Honda-SOHC

SOHC.co.uk Forums => Project Board => Topic started by: CR21 on May 14, 2016, 10:12:06 PM

Title: CR750 replica build
Post by: CR21 on May 14, 2016, 10:12:06 PM
So the build begins!

I have been wanting to undertake another project since the TA replica I took on over three years ago, this is due for its final commissioning at the end of this month where it will be put through its paces on the dyno (worried face!)

Since I began the TA125 build, I have become fascinated by the world of 70s race bikes, the history, stories and machinery of that era are very  intriguing. This led me on to discover a machine which I did not know a huge amount about, of course its roots are from the CB750 a bike in itself has left a very prominent flag in motorcycling.

The CR750

A beautiful build of a previous replica, used for inspiration!

(https://farm5.staticflickr.com/4403/36272196223_db55fa1529_z.jpg)


(https://farm5.staticflickr.com/4399/36272196143_12249d5043_z.jpg)


(https://farm5.staticflickr.com/4349/36272196073_46c9b80263_z.jpg)

(https://farm5.staticflickr.com/4353/37085476395_4909eab537_z.jpg)

To be honest at first the CR750 appealed to me completely on an aesthetic level, just look at it! The lines of the pipes, the tank, the fairing lines and the stance of the bike. This winning the Daytona ridden by Dick Mann in 1969 must have been an incredible sight.

To cut a long story short, I want to build a replica. This will by no means be an "unlimited budget" replica, alike some bikes that have been built. But it will aim to be as "accurate" as the budget allows, fabricating and sourcing replica parts as I go along will hopefully keep the budget on track.

I had anticipated that this build was going to have to happen some time ago, when I decided to place a deposit down on a fuel tank. Having previously constructed the replica tank for my TA125, I contemplated fabricating a tank for the CR replica however after seeing ASA MOYCE'S beautiful work, he was the only man for the job. Last year I paid a deposit in order to be on the waiting list, of which the build slot is slowly approaching around July.

(https://farm5.staticflickr.com/4400/36944425071_9ccab138d1_q.jpg)

After committing to the project and a fuel tank I then needed to source a bike! If any forum member happens to have this kit of bits boxed up in the loft, please get in touch  ;D

(https://farm5.staticflickr.com/4352/36944425021_80dc79a558_z.jpg)

After many weeks searching around and bidding on bikes which went way out of my budget, I decided to price up building the CR750 "basis" (CB750 rolling chassis + engine) from parts. This came in at about the same cost as some of the project bikes. I generally have the attitude that some original bikes with patina should not be modified, so could not face "cutting up" a good one.

I searched and searched, and ended up buying a CB750 K4 USA import, this had; non-standard pipes, different forks, repairs needed doing to the frame and crankcases, a few modifications. But all in all a fairly original bike which I could face stripping for the starting block of the CR build. I stripped the bike one Saturday, and all of the parts that were not required (most of the bike) were sold off online, mainly to members of the Honda forums.

This made the "donor bike" a little more affordable. I intend on fabricating my own replica parts that I deem to be too expensive from some suppliers, and using other fantastic suppliers for accurate components such as the tank and exhausts.


There is a huge amount of information out there regarding the CR750s, I have found out more information on the CR750 in one evening than even exists on the TA125 so I feel that although this build is larger and will cost a lot more than the TA, the information and fellow enthusiast group will be a great help. I have been emailing a few different experienced builders of these machines, some of which have been extremely helpful so far so thank you guys it's much appreciated.

The donor bike in all its glory, what a beast of a bike!

CB750 K4:

(https://farm5.staticflickr.com/4340/36944424961_2f6aa26876_z.jpg)

(https://farm5.staticflickr.com/4396/36944424891_b854b2d8fb_z.jpg)


Now stripped to leave the rolling chassis:

(https://farm5.staticflickr.com/4406/36944425361_c0fb5c4dc4_z.jpg)

(https://farm5.staticflickr.com/4341/36944425291_e8bb6dcf69_z.jpg)

(https://farm5.staticflickr.com/4386/36944425181_86e679b2b1_z.jpg)

During the strip down I was very pleased with how everything has come off of the bike, and how original the bolts and small components have been, which will hopefully be reflected inside that big engine.

Of course there are a few hurdles:


- the chain has damaged the crankcases at some point in the past and this has been repaired with epoxy (will be cleaned, dressed and delivered to a local master aluminium welder!) 

(https://farm5.staticflickr.com/4351/36272504063_f44f3f98e2_z.jpg)

- Some cowboy repair merchant was seeing double when fitting a side stand in the past:

(https://farm5.staticflickr.com/4420/36944425461_d073b4ab8f_z.jpg)

But all in all I feel that it should make a good basis, and as some of you may have noticed, the front end has previously been swapped for an earlier set-up. There is no sign of accident damage to the frame. However this is another reason I was interested in this bike, as I wanted to run the early fork/brake set-up as it is more sympathetic to the original CR look.

I have managed to source the opposing "mirrored" caliper bracket in order to run the dual disk set-up. This is a fairly rough casting but I feel it will clean up relatively well. This will allow me to mount the "original style" CR front mudguard to the bike. As fork stanchions are relatively easy to get hold of I will be replacing these with pattern ones.

However I am still on the lookout for a second caliper. And some drawings/measurements for a CR mudguard.


--

I will be documenting the build of this bike in two locations. On the air-cooled RD forum (where the TA125 replica build thread is) and on the SOHC HONDA U.K forum.

I received a huge amount of advice from the members of the air cooled Rd forum and if it is welcome on the forum I would like to keep people posted on the "next project" (apologies it is not a YAMAHA!)

I think that is enough rambling for now, here goes another long build :D I can't wait!

All the best,
CR21/RD17
Title: Re: CR750 replica build
Post by: MarkCR750 on May 14, 2016, 11:13:02 PM
Good luck with your build, I got mine on the road last week although it's a long way from finished ,for example it currently has a 4 into 1 and Honda racing colours instead of the CR paint job and 4 into 4, I can however report that they are great fun to ride and the twin disc set up works well, Ive lost count of the amount of people that have stopped me to talk about it at petrol station/traffic lights etc, so be aware it will attract a lot of attention when you have finished it!, as I said good luck I hope it goes well.

Title: Re: CR750 replica build
Post by: CR21 on May 14, 2016, 11:14:08 PM
Good luck with your build, I got mine on the road last week although it's a long way from finished ,for example it currently has a 4 into 1 and Honda racing colours instead of the CR paint job and 4 into 4, I can however report that they are great fun to ride and the twin disc set up works well, Ive lost count of the amount of people that have stopped me to talk about it at petrol station/traffic lights etc, so be aware it will attract a lot of attention when you have finished it!, as I said good luck I hope it goes well.

Hi Mark, I have been following your build. Fantastic work I am glad you have it ready for the summer :)

Cheers
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on May 14, 2016, 11:26:48 PM
Here's a link to the race that gave the bike it's reputation, a few good shots of the bike too.

https://www.youtube.com/watch?v=FHlFH8hxMyQ
Title: Re: CR750 replica build
Post by: westfieldandy on July 26, 2016, 04:39:41 PM
Hi,

If you need any advice /assistance.

please dont hesitate to call, been developing a race winning cr for ages,

see https://youtu.be/cOcQZ2oVeFE.   for video of "Award winning Honda 750 Cove Torque"

and my website www.good-bits.co.uk

advice for free, and hopefully i can help with your build

andy
Title: Re: CR750 replica build
Post by: CR21 on July 27, 2016, 05:46:32 PM
Thanks for the replies, all help is useful so the offer is much appreciated. I am aiming to pick the project back up in September  :)

Cheers
CR21
Title: Re: CR750 replica build
Post by: Laverda Dave on August 17, 2016, 05:35:08 PM
Good luck with build and enjoy the long nights in the shed  :).
One piece of advice though, get the frame checked for alignment before you paint it especially as it's been fitted with another front end.
The last two restorations I've completed both had frames that appeared fine but were both out of alignment once placed in a jig. It cost me £80 to have each one checked and straightened. Money well spent, the last thing you want is to finish a build only to find it doesn't handle.
You will need to fit the engine (bare crankcases will do,it doesn't have to be together), the swingarm, rear shocks, back wheel and the top and bottom yokes to be really thorough.
I used Hybrid motorcycles in Sarratt,  Middlesex.
Dave
Title: Re: CR750 replica build
Post by: Johnwebley on August 17, 2016, 06:48:16 PM
hi,

 I do enjoy your TA125 rebuild ,and I am sure the CR750 will be to the same perfection,


  regards

 John
Title: Re: CR750 replica build
Post by: CR21 on August 26, 2016, 09:58:40 PM
hi,

 I do enjoy your TA125 rebuild ,and I am sure the CR750 will be to the same perfection,


  regards

 John

Hi John thanks, it turned out alright in the end  :D

Anyway back to the CR!!

So a BIG package arrived today... I felt like a little kid opening it up :D All I can say is that I am very chuffed!

(https://farm5.staticflickr.com/4421/36251042824_277d099e61_z.jpg)

(https://farm5.staticflickr.com/4351/36897902526_d4d6dfdc0f_z.jpg)

(https://farm5.staticflickr.com/4366/36272946033_7d65506b52_z.jpg)

(https://farm5.staticflickr.com/4427/36897902456_97628ccf16_z.jpg)

(https://farm5.staticflickr.com/4389/36272945943_1043a0b94b_z.jpg)

(https://farm5.staticflickr.com/4352/36944867061_9218ac8458_z.jpg)

(https://farm5.staticflickr.com/4333/36272945053_8a5799e95a_z.jpg)

(https://farm5.staticflickr.com/4421/36944867821_5eaafd15b7_z.jpg)

(https://farm5.staticflickr.com/4437/36251042694_876221b4fb_z.jpg)


Cheers
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on August 27, 2016, 07:25:11 AM
Very nice, are they from mr Boyce?
Title: Re: CR750 replica build
Post by: CR21 on August 27, 2016, 09:45:23 AM
Very nice, are they from mr Boyce?

They certainly are  ;)
Title: Re: CR750 replica build
Post by: CR21 on October 11, 2016, 01:13:14 PM
So the build is progressing slowly.

I am currently searching for the following:

- CR750 original style tank strap.
- CR750 RC seat (not sure about the meadspeed unit)



The fueltank is strapped into place on the rear of the tank only, the front is held in with rubber mountings. Unlike the Yamahas which are often strapped front and back.

The difficult thing is getting hold of a ‘replica’ fueltank strap to be able to do the tank justice! I could use a Yamaha part that would work well, but I would rather not. Just to add detail to the build and some originality. The only thing I don’t like about the RC style strap is that the bare steel loop of the strap sits onto the aluminium tank so I think I may have to sheath this somehow. I can make up the stainless parts by hand bending however the challenge comes with the rubber part!

(https://farm5.staticflickr.com/4346/36251129814_4e5c1b6d22_z.jpg)

(https://farm5.staticflickr.com/4373/36916128042_bf39a5cfa1_z.jpg)

Stock extrusions exist but after quite a bit of research there is not a suitable stock part that I could use….

This type of part would have been overmoulded over the wire sections, which is expensive. As well as moulding, extrusion is an option for manufacturing this part however again there is a tooling cost associated with this, and it is high as I would only want a very low volume of parts.

A company named ‘CR750 RSC - Works Motorcycles & Parts’ who I came across on Facebook make a replica strap that is close to the part that I am after however I would like a go at making one myself. Some of their other products are fantastic including frame kits and machined parts – well worth a look! This is the replica strap available, similar to what I would like to achieve:

(https://farm5.staticflickr.com/4355/36251129944_be4ef643f3_z.jpg)

I have ordered some stainless bar to have a play with bending it, I also ordered up a few Yamaha straps to see if any of them are close to the part I am after and could be utilised/modified. When I get fed up of trying to sort this out I will just order the available part and see if I can tidy it up?

I have some time booked off over soon, and I intend on building the twin disk front end up, de-lugging the frame and adding the seat and tank mountings so that I can finally look at the tank on the bike and get stuck into the project!

Cheers!
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on October 11, 2016, 04:52:39 PM
Here is the twin disc guide that I used, I found it a very easy job, people on various threads in the states seem to struggle, not at all sure why, maybe we're cleverer than our Yankee friends? 😄, make sure that you use a master cylinder that is designed for a twin disc setup, i used one from a 97 fire blade , works well but maybe wouldn't suit your bike as I think your going for a more original look, GL1000 master cylinder may be better for you, yes the mead speed seat looks nothing like the original, I used it because I needed somewhere to hide the battery, the original CR had a tiny tail cowl.
http://www.dotheton.com/forum/index.php?topic=1525.0
Title: Re: CR750 replica build
Post by: CR21 on October 11, 2016, 11:13:31 PM
Here is the twin disc guide that I used, I found it a very easy job, people on various threads in the states seem to struggle, not at all sure why, maybe we're cleverer than our Yankee friends? 😄, make sure that you use a master cylinder that is designed for a twin disc setup, i used one from a 97 fire blade , works well but maybe wouldn't suit your bike as I think your going for a more original look, GL1000 master cylinder may be better for you, yes the mead speed seat looks nothing like the original, I used it because I needed somewhere to hide the battery, the original CR had a tiny tail cowl.
http://www.dotheton.com/forum/index.php?topic=1525.0

Hi Mark!

Thanks for the link, I have already linked from a thread from this forum (may be your build thread) its very useful. That may be the case  ;D

Cheers for the heads-up on the master cylinder, I was planning on using a GL1000 one.

Tricky one the seat as I am after one with a cover/seat swab as trimming can soon get very expensive! I have a Meadspeed unit that I picked up but I am not sure if I am going to use it.

What ignition did you use Mark? I was thinking of using the DYNA total loss system.

Cheers!
CR21
Title: Re: CR750 replica build
Post by: UK Pete on October 12, 2016, 09:13:08 AM
WOW i have to say the petrol and oil tank are a work of art
What do other people use for the strap
pete
Title: Re: CR750 replica build
Post by: CR21 on October 12, 2016, 09:36:37 AM
WOW i have to say the petrol and oil tank are a work of art
What do other people use for the strap
pete

Hi Pete, they are the maker is a true craftsman! Other people have used the Yamaha strap in the past, or the reproduction one,

Cheers
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on October 12, 2016, 12:56:05 PM
Here is the twin disc guide that I used, I found it a very easy job, people on various threads in the states seem to struggle, not at all sure why, maybe we're cleverer than our Yankee friends? 😄, make sure that you use a master cylinder that is designed for a twin disc setup, i used one from a 97 fire blade , works well but maybe wouldn't suit your bike as I think your going for a more original look, GL1000 master cylinder may be better for you, yes the mead speed seat looks nothing like the original, I used it because I needed somewhere to hide the battery, the original CR had a tiny tail cowl.
http://www.dotheton.com/forum/index.php?topic=1525.0

Hi Mark!

Thanks for the link, I have already linked from a thread from this forum (may be your build thread) its very useful. That may be the case  ;D

Cheers for the heads-up on the master cylinder, I was planning on using a GL1000 one.

Tricky one the seat as I am after one with a cover/seat swab as trimming can soon get very expensive! I have a Meadspeed unit that I picked up but I am not sure if I am going to use it.

What ignition did you use Mark? I was thinking of using the DYNA total loss system.

Cheers!
CR21
I used the piranha system that was on the donor bike, god knows how old it is but it works, but I've kept the alternator etc because mine is for road use, I assume that you are removing your alternator to be closer to the original?
Title: Re: CR750 replica build
Post by: CR21 on October 12, 2016, 01:14:43 PM
Here is the twin disc guide that I used, I found it a very easy job, people on various threads in the states seem to struggle, not at all sure why, maybe we're cleverer than our Yankee friends? 😄, make sure that you use a master cylinder that is designed for a twin disc setup, i used one from a 97 fire blade , works well but maybe wouldn't suit your bike as I think your going for a more original look, GL1000 master cylinder may be better for you, yes the mead speed seat looks nothing like the original, I used it because I needed somewhere to hide the battery, the original CR had a tiny tail cowl.
http://www.dotheton.com/forum/index.php?topic=1525.0

Hi Mark!

Thanks for the link, I have already linked from a thread from this forum (may be your build thread) its very useful. That may be the case  ;D

Cheers for the heads-up on the master cylinder, I was planning on using a GL1000 one.

Tricky one the seat as I am after one with a cover/seat swab as trimming can soon get very expensive! I have a Meadspeed unit that I picked up but I am not sure if I am going to use it.

What ignition did you use Mark? I was thinking of using the DYNA total loss system.

Cheers!
CR21
I used the piranha system that was on the donor bike, god knows how old it is but it works, but I've kept the alternator etc because mine is for road use, I assume that you are removing your alternator to be closer to the original?

Hi Mark,

I see, I have seen the piranha systems on Yamahas but I have never used them. I run a PVL style total loss on my TA125. Yes the alternator will go I just need to decide what ignition set-up to use. Really it will depend on reviews and price - I need to do some research :)

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on November 16, 2016, 09:10:57 PM
This thread has been very quiet for a while... But I have been doing a huge amount of research, and have become somewhat CR obsessed!

Picking back up on the tank strap:

I have managed to source the correct rubber part to fit in between the steel bands, and have ordered some stainless steel rod to allow me to make my own replica tank strap.

Frame modifications

This research is what I have been whittling away at ready for a Christmas frame altering session. This is the list so far:

- De-lug all road mounts.

- Fit machined and fabricated rear sets. I have produced a CAD model and drawings for the rear sets, which like the image below have a 12mm thick boss, which houses the footpeg and mounts for the brake pedal and exhaust. This part is welded in-between two folded sections to create a triangular bracket. These 'inserts' will either be waterjet cut or I will machine them. Luckily I have managed to get hold of a sketch with measurements from a kit bike to be able to accurately place the rearsets onto the frame.

(https://farm5.staticflickr.com/4387/36251413384_edaaeced8a_z.jpg)

(https://farm5.staticflickr.com/4378/36251413334_8bf25d8ca3_z.jpg)

On these rearsets I am going to mount a set of replica aluminium pegs with the all important cured rubber over moulded grip. These are replicas cast from the original parts, with a bronze bushing pressed into them. They will be held into place by a custom 'replica bolt' which I will turn up.


Replica footpeg clamping bolt CAD:

(https://farm5.staticflickr.com/4386/36273299293_b62b0e924d_z.jpg)

Onto these rear sets mount the rear exhaust hangers, the brake pedal again a cast item with a rubber over moulded grip. The footpeg mounts through a bush, and depending on the gear set-up is on the left or the right side. The rear brake is cable operated with a large and very complex cable, a cable stop will be placed onto both rearsets to allow for both left and right gear changes.

Replica Brake cable 'stop':

(https://farm5.staticflickr.com/4331/36251413264_b69e718e88_z.jpg)

(https://farm5.staticflickr.com/4393/36273299153_abccb55fac_z.jpg)

The left gearchange is simple, as it uses a conventional style pedal in reverse from the output shaft. However the 'special' gear change option was to have a changeover shaft for British racers, this comprises of a linkage assembly, bearing holders and another frame modification to house an olive bush. This is a modification that I would like to fit at a later date so this is another frame modification.

(https://farm5.staticflickr.com/4391/36273298893_73499696f6_z.jpg)

The fuel tank mountings are fairly simple, it mounts at the front with the original HONDA rubber mounts, and at the rear it is held in with the replica strap. The frame is modified with an added 'Arc' which braces the frame for the tank strap, and provides a mounting point for the front of the seat. Again I have managed to acquire a drawing for this part  ;)

The rear of the frame is cut off, and the seat support loop is lowered. I may also add a rear frame loop as well if I feel that the seat requires supporting.

Other frame mods include an additional steering damper (a simple flanged plate that fits ontop of the lower yoke around the left fork tube and is secured by sharing the pinch fork pinch bolt) the other end of the damper fits to the frame rail underneath the tank with a clamp, a detail that is still to be resolved.

Fairing

The fairing is mounted in three places, at the headstock with the conventional 'pinched tube' onto a bracket, either side of the engine mounts to support the rear of the fairing, and on the frame rails by the headers to support the lower front part of the fairing (I believe this was a modification rather than being original however I don't want the fairing flapping.

I have managed to get a set of accurate rear fairing brackets that bolt onto the rear engine mounting plates, which again are really nicely made parts and are supposedly very accurate, similar to the ones below but detailed in a different way:

(https://farm5.staticflickr.com/4365/36251413024_ef78ccd5ef_z.jpg)[/url]

The front 'main' fairing bracket that I have purchased is a 'tribute' part that is relatively close to the original, however I may make my own/try to source a more original one further down the line.

The fairing has been a real head-scratcher, as many replica fairings just do not look right in my eyes, this could be down to decal placement, or even the fitting of the fairing itself, I am really unsure. This led to contacting many people that have built replicas including some self-confessed classic racing Honda 'Anoraks' in order to trace down a good replica fairing.

I eventually traced down a fairing from a supplier in London and the story says that he purchased the moulds from a guy who made the mould from a 'Genuine CR Daytona fairing' so it should be pretty spot on. I am happy with the shape, and it seems to be the best that I can find. Listening to various recommendations from different people who have built accurate replicas seems to be the way forward with this build, there is a wealth of knowledge of these bikes that simply did not exist during the TA125 build and it is a real help.

After looking at many available seats on the market I was not really happy with any of them, the Meadspeed unit seems to be reasonable quality but the shape is wrong. The only seat that I did like was the Airtech seat but with shipping and a swab base it becomes a ludicrous amount! Luckily I have managed to track down a guy who has a seat mould, supposedly taken again from an original Honda racing part. The aim is to borrow the mould and create a seat for my bike potentially from Carbon  :) which would be great!

Wheels

The front wheel aside from having the double disk conversion is pretty straight forward. The hub will be turned down to remove the central cast ribs to resemble the original magnesium CR part.

The rear hub is a point of discussion of these CR bikes. Originally the CR had a twin leading shoe, cable operated brake cast in magnesium, a real work of art and a focal point of the bike. Sadly these hubs were only ever made in very small batches, and any replicas are also made in small runs and are massively expensive from £3500 upwards  :o For me this is a step too far financially, and I will be finding an alternative way of achieving a similar look. There is a company in America who are making a replica back plate to fit the standard K series CB750 hub, however this is still in development and again is not cheap. I think I will try to work out a way of mounting a cable boss to the existing brakeplate unless a replica part becomes financially viable.

Exhausts

I think that a good chunk of the CR appeal comes from the exhausts, not only the sound but the look of the original 'Swept' pipes. After researching this topic it appears that there is only one supplier who makes these exhausts properly, hydroformed with a welded seam, complete megas with a reverse cone and smoothly bent header pipes they really are a work of art! Made by Simon Tappin, these will be going on my bike!

(https://farm5.staticflickr.com/4370/36273298863_cc16e025c5_z.jpg)

(https://farm5.staticflickr.com/4367/36251414054_b158b96c2a_z.jpg)

Clip on handlebars

The original CR clip on handlebars were hinged around the yoke and clamped into place by a pinch bolt, this was for ease of disassembly without the need to remove the top yoke. As far as I know nobody makes a replica clip on, and as I want clip ons as close to the original I am going to have to make them myself! "Why" You may say when standard clip ons that will do the same job are less than £100? Well it's the details that will hopefully make this bike, and it is a good challenge for me to get stuck into!

The original CR clip ons were a two-piece clamp, cast in Titanium and then had a tube attached to the casting to form the handlebar. I doubt I wil be using titanium, however I will aim to make the parts as light as possible either in a racing steel or aluminium. In order for the master cylinder to clear the clamp on the right unit the clip on needs to be angled and kinked to prevent a clash. I have drawn the parts up using a CAD program to be able to create the design, look at tolerances and of course check the clearance angles with the master cylinder.

(https://farm5.staticflickr.com/4388/36251413884_6b9fe341f5_z.jpg)

RHS CLIP:

(https://farm5.staticflickr.com/4334/36251413544_fc8a2f3bc9_z.jpg)

LHS CLIP:

(https://farm5.staticflickr.com/4332/36251413504_637168cec7_z.jpg)

All in all the preparation seems to be going well for the frame modifications at Christmas  :) Full steam ahead!

I have referred to people without naming them in this post quite a lot, and this is because most of them are not part of forums or even online at all.  I have been overwhelmed with the help and enthusiasm from suppliers and people who are in the Honda scene, thanks to you guys if you are reading this!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on November 16, 2016, 09:14:36 PM
To progress with the CR750 rearsets, I worked from a number of images and sketches that I have been collecting over the last two years. It appears that there may have been two types of CR750 rear sets available with the kit originally supplied by Honda. Both types were folding, one sprung and one un-sprung. I have decided to go with the un-sprung set for simplicity, and I am not entirely sure if the sprung units I have seen are replica parts or original parts. I can also get a nice replica set of footpegs from an American supplier. As mentioned in my post above, the rear-set ‘boss’ is a relatively simple form, that will be machined from steel, cut from one direction, then spot faced, drilled and tapped for the bolt.

I had toyed with the idea of making the entire rear-set machined, as the profile is very simple and there is machining to be done on the part anyway, however to be faithful to the original bike I will fabricate the hanger from two sheet metal halves. These halves are just simple folded profiles that are butt welded to form a central seam, and then the boss is welded into position around the perimeter.

(https://farm5.staticflickr.com/4344/36916722552_d4af632cdb_z.jpg)

(https://farm5.staticflickr.com/4366/36945539341_a164379613_z.jpg)

(https://farm5.staticflickr.com/4439/36273616883_b3372a03a0_z.jpg)


In order to save on fabrication time, I have modelled up the rearsets in a CAD package. These are very simple parts to model but this allows me to consider bush tolerances for the peg, and also the ‘flat pattern’ for the sheet metal work.  When modelling these parts in CAD I start off with a flat sheet, mark out bend lines and generate the bends, very much like the manual process at a bench with marking blue and a fly press, but in the digital form.

(https://farm5.staticflickr.com/4353/36916722362_9050ba3421_b.jpg)

This digital CAD model can then be ‘flattened’ to give me a profile to work with with bend lines in the correct places, which will untimely save time and head scratching when fabricating and will allow me to fabricate the parts as I intended and have planned. Of course these parts should then fit nicely around the boss for welding into place.  Overkill yes on such a simple part – but it is good to try these things out, and with the angles involved to interface with the frame, it should prevent errors.

(https://farm5.staticflickr.com/4440/36945539611_171615ab2d_z.jpg)

I will follow the same process for the frame brackets, which will also allow me to build up an inventory of drawings and models for reference.

Cheers, 
CR21
Title: Re: CR750 replica build
Post by: onethumb on November 17, 2016, 10:06:21 AM
That is embarrassingly good. It puts most shed builds (mine included) completely in the shade.

CR21 you've got skills.





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Title: Re: CR750 replica build
Post by: Nurse Julie on November 17, 2016, 10:51:23 AM
WOW !!! That's very impressive. Whatever happened to the days of scribbles on the back of a fag packet  :) :) :)
Title: Re: CR750 replica build
Post by: onethumb on November 17, 2016, 11:04:54 AM
Nurse Julie I still do.  Hence the mess up with my frame. 


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Title: Re: CR750 replica build
Post by: Nurse Julie on November 17, 2016, 11:41:42 AM
Nurse Julie I still do.  Hence the mess up with my frame. 


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I'm please I'm not the only Luddite on here  ::) ::) ::)
Title: Re: CR750 replica build
Post by: MCTID on November 17, 2016, 12:33:47 PM
Scott (CR21) is a Designer in real life. He's a smart Lad - and I'm looking forward to seeing his finished CR750.
Title: Re: CR750 replica build
Post by: Chris400F on November 17, 2016, 01:04:34 PM
Scott (CR21) is a Designer in real life.
So he has a head start then! But if you have the knowledge, enthusiasm and facilities then you may as well make the most of them.
Even so the amount of research he has done and the attention to detail is very impressive.
Title: Re: CR750 replica build
Post by: CR21 on November 17, 2016, 10:33:04 PM
Hi guys,

Thanks for the replies. There are some extremely high-quality builds on this forum, and a lot of fantastic support. If this build can come out anywhere near some of the builds I have seen on this forum I will be chuffed  ;D

Cheers!
CR21
Title: Re: CR750 replica build
Post by: CR21 on December 01, 2016, 07:07:07 AM
Just a quick update:

I have made some progress on the other frame modifications, drawings are all completed for the rear sets ready for Christmas manufacture and replica pegs have been ordered.

The oil tank mounting on these bikes are a little fiddly, this is what I make of it so far:

The oil tank is 'suspended' into the frame, it is hung from the top from two L-shaped brackets and rests on rubber seats on the bottom supported by more L-shaped brackets either side like the reference image below:

(https://farm5.staticflickr.com/4344/36928060342_009133d76c_z.jpg)

(https://farm5.staticflickr.com/4403/36928060232_ae11a4ceec_m.jpg)

Top mounting brackets (to be modified for a more triangular profile).Waiting for grommets to arrive to complete the profile:

(https://farm5.staticflickr.com/4425/36956970841_03e10021ae_z.jpg)

Bottom brackets:


(https://farm5.staticflickr.com/4337/36928060442_d8aa83888e_z.jpg)


(https://farm5.staticflickr.com/4384/36928060282_d541e3d761_b.jpg)

With the help of a member from the CB750 forum who has built a fantastic replica, I have managed to obtain measurements from his CR750 catch tank. Another piece of the jigsaw! Modelled up in CAD for future reference. This will be fabricated in Aluminium.

(https://farm5.staticflickr.com/4352/36956971011_43b130bd85_z.jpg)

(https://farm5.staticflickr.com/4436/36956970941_b6363a185a_b.jpg)

(https://farm5.staticflickr.com/4401/36956970871_d49a1a03ea_b.jpg)



That is all for now,

Cheers
CR21

Title: Re: CR750 replica build
Post by: CR21 on January 04, 2017, 07:21:00 AM
Hi all,

The CR donor was removed from the shed:

(https://farm5.staticflickr.com/4419/37043594851_ba63f4321c_z.jpg)

After a long game of 'engine wrestle' the engine was removed from the frame and the rest of the parts stripped off!

What a lump!!
(https://farm5.staticflickr.com/4414/37014062732_45656a15d0_z.jpg)

(https://farm5.staticflickr.com/4371/37043594791_8c4ce81c8c_z.jpg)


Now for a day of de-lugging and working out these chassis mods. Rearset fork bosses all machined up ready to accept the sheet-metal work:

(https://farm5.staticflickr.com/4347/37043594661_86fcdf7c59_z.jpg)

(https://farm5.staticflickr.com/4418/37043594531_302736e7a0_z.jpg)

More to come over the next few days,

Cheers!
CR21
Title: Re: CR750 replica build
Post by: CR21 on January 04, 2017, 07:21:25 AM
Made some progress today:

****  :o CB750K PURISTS LOOK AWAY NOW  :o *****

5 hours of de-lugging later and the frame is sorted  ;) Took a while as I did not want to damage the frame...

(https://farm5.staticflickr.com/4423/36996160436_2e6e3aa950_z.jpg)

(https://farm5.staticflickr.com/4362/36996160556_b6ab6b2155_z.jpg)

The most difficult of all was definitely the side-stand bosses, and I had two of them  :'( :D

(https://farm5.staticflickr.com/4382/36371861183_665f74a099_z.jpg)

(https://farm5.staticflickr.com/4426/36371861793_987b27eeed_z.jpg)

The frame looks much cleaner de-lugged, I must say I think that the build quality of these frames is pretty poor! Compared to the Yamaha frames that I have worked on its really rather poor  :-\

(https://farm5.staticflickr.com/4431/36371861403_7f207655a6_z.jpg)

I faced off a bit of tube to keep the frame from pulling in when removing and adding bracing in this area. Tank placed onto the frame for the first time it was good to see! (the seat is just being used for a mock-up I will not be using this for the final build). 

(https://farm5.staticflickr.com/4407/36371861743_e397c28d7d_z.jpg)


On with the rear-set sheet metal work, pattern worked from, folded, cut back, jigged and welded. Then the final fit on the boss to be welded in place tomorrow morning and fitted.

(https://farm5.staticflickr.com/4383/36371861673_d22b93ebff_z.jpg)

(https://farm5.staticflickr.com/4430/36996160856_c003592f0d_z.jpg)

(https://farm5.staticflickr.com/4350/36371861303_88c784ee33_z.jpg)

(https://farm5.staticflickr.com/4360/36371861573_3fe124454d_z.jpg)

(https://farm5.staticflickr.com/4375/36371861523_432d2515f6_z.jpg)

Cheers!
CR21
Title: Re: CR750 replica build
Post by: onethumb on January 04, 2017, 02:43:59 PM
Sweet work. Makes me embarrassed to put my build up now. 


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Title: Re: CR750 replica build
Post by: Johnwebley on January 04, 2017, 02:54:35 PM
this is brilliant,

   the quality is superb,did you do the folding/bending and welding ??
Title: Re: CR750 replica build
Post by: CR21 on January 04, 2017, 07:52:05 PM
Thanks guys!

Yes I play around with the fabrication and the odd bit of machining,  a good friend of mine is 100 times better than welding than me, and you guessed it he does my welding  :)

Cheers CR21
Title: Re: CR750 replica build
Post by: CR21 on January 04, 2017, 10:03:29 PM
Hi all,

Made some progress today:

Rearset plates all welded up now, and the footpegs fit nicely in the slots. I am going to tweak the footpegs to the brackets so that they sit level on the frame at a later date as I want to make sure they are going to be level when weight is placed onto them. I took this into account when drawing the footpeg bosses.

(https://farm5.staticflickr.com/4375/37043805901_6bfc2b9fd0_z.jpg)

I still have the brake pedal stop and cable guide to add, but again I will wait until the rear-sets are on the bike and the assemblies are 'dry built'.

In order to jig the rear-sets accurately onto each frame tube I cut a piece of tube and faced off each end on the lathe. This keeps the brackets parallel to each other when they are tacked onto the frame:

(https://farm5.staticflickr.com/4416/37186059455_8c213da7e8_z.jpg)

The first attempt at shaping the rear-set to fit around the frame tube. This needs tweaking again to bring it closer to the frame before the final fitting, tedious but very important  ???

(https://farm5.staticflickr.com/4442/37043806561_d519f5eaa3_z.jpg)

Onto the frame and seat brace, this rather surprisingly fits between the seat and the frame  ;) The seat slides into two small hooks on this bracket and the tank strap also hooks onto it. This brace is shaped to accept the oil filler for the tank, similar to the shown in the image below:

(https://farm5.staticflickr.com/4386/37043805781_4b8d7dc426_z.jpg)

L shape folded on the folding table:

(https://farm5.staticflickr.com/4367/37186059175_852c925525_z.jpg)

(https://farm5.staticflickr.com/4358/37186058625_03d88005d9_z.jpg)

Welded:

(https://farm5.staticflickr.com/4357/37186059075_827949e0e5_z.jpg)

Linished back and marked out oversize so that it can be fitted to the frame:

(https://farm5.staticflickr.com/4368/37043806191_3e6e136bd9_z.jpg)

Cut on the bandsaw supported by a 'strategically selected' piece of palletwood:

(https://farm5.staticflickr.com/4424/37186058945_cb5e66d8c3_z.jpg)

Now for the infilling strip for the curved session, I cut a strip and then rolled it to fit the radius:

(https://farm5.staticflickr.com/4438/37014297532_eb7f0634bc_z.jpg)

(https://farm5.staticflickr.com/4394/37043805991_71e3d45e77_z.jpg)

All blocked up for tack welding and seaming in the morning. Of course this will be linished back afterwards:

(https://farm5.staticflickr.com/4430/37186058495_6d48cb2827_z.jpg)

I started to play with the seat hooks at the end of the day, however I have decided to make them again so that they can be welded properly along another folded edge like the image of the other bracket above. The gauge of material for the hooks looks heavy here, but I feel that it is needed to secure the seat properly as the tab is so small.

(https://farm5.staticflickr.com/4394/37186059555_a01069f778_z.jpg)


All for now hopefully the frame will be all welded up tomorrow!

Cheers
CR21
Title: Re: CR750 replica build
Post by: K2-K6 on January 04, 2017, 10:37:30 PM
Nice fabrication work.

I noticed that the seat tab example photo shows the tabs as a Z shape so that they've got more weld shear plane rather than just butt welded to the flat steel.

Did you have to heat the heavy gauge footpeg block while welding to get a good flow into the weld? As it's usually quiet difficult to get two different metal thicknesses to melt at the same time. I'm just interested in the method he's used.

Did you get a solution for the tank strap with that rubber section you have previously asked about?
Title: Re: CR750 replica build
Post by: CR21 on January 04, 2017, 10:53:49 PM
Nice fabrication work.

I noticed that the seat tab example photo shows the tabs as a Z shape so that they've got more weld shear plane rather than just butt welded to the flat steel.

Did you have to heat the heavy gauge footpeg block while welding to get a good flow into the weld? As it's usually quiet difficult to get two different metal thicknesses to melt at the same time. I'm just interested in the method he's used.

Did you get a solution for the tank strap with that rubber section you have previously asked about?

Hi K2-K6,

Thanks. yes if you read the end of my last post this is what I am referring too, the ones that I will use on the bike will be welded along the flat section for strength, I also think these look neat just welded up each side of the flat. The torch would have been directed predominately towards the boss to prevent the sheet from melting away, aside from that I guess it's just experience!

Yes that is all sorted, more to come  :)

Cheers
CR21

Title: Re: CR750 replica build
Post by: paul G on January 05, 2017, 08:18:45 AM
Nice fabrication work.

I noticed that the seat tab example photo shows the tabs as a Z shape so that they've got more weld shear plane rather than just butt welded to the flat steel.

Did you have to heat the heavy gauge footpeg block while welding to get a good flow into the weld? As it's usually quiet difficult to get two different metal thicknesses to melt at the same time. I'm just interested in the method he's used.

Did you get a solution for the tank strap with that rubber section you have previously asked about?


Hi K2-K6,

Thanks. yes if you read the end of my last post this is what I am referring too, the ones that I will use on the bike will be welded along the flat section for strength, I also think these look neat just welded up each side of the flat. The torch would have been directed predominately towards the boss to prevent the sheet from melting away, aside from that I guess it's just experience!

Yes that is all sorted, more to come  :)

Cheers
CR21


Some stunning work going on here  ;D ;D
Title: Re: CR750 replica build
Post by: CR21 on January 05, 2017, 11:49:18 PM
Thanks guys it is good to get stuck in and focus on the build  ;)

Some progress from today!

- Brace welded
- Brake cable stops made
- Front spigot made for the fairing carrier
- Welded the tank strap loops around the rubbers
- Debossed the top yoke and started to re-shape to 'CR spec'

Tank/seat brace welded up and linished back:

(https://farm5.staticflickr.com/4430/37186590205_3df27853f0_z.jpg)[/url]

(https://farm5.staticflickr.com/4409/36350002564_b4aafabe20_z.jpg)


Offered up to the frame and tank etc:

(https://farm5.staticflickr.com/4410/36350002534_9921bd35dd_z.jpg)

I shaped either side of the bracket to fit tightly between the frame tubes, however I was unhappy with the rear of the brace where it was 'open'. So this was plated up, linished back and then shaped the same as the front section to fill the gap:

(https://farm5.staticflickr.com/4410/37044353071_62126382d6_z.jpg)

Measured out using the shock mounts as a datum:

(https://farm5.staticflickr.com/4346/36350002464_ef6ec46ca2_z.jpg)

Now ready for welding tomorrow morning:

(https://farm5.staticflickr.com/4393/36372530983_c55d75fa93_z.jpg)

Front spigot made and shaped out of steel tube, quick bit of turning to make the clamping boss. I shaped the rear of this with a file for it to sit nicely onto the tube and for a better fit whilst welding. I will add the slit after welding and will drill out one side of the clamp.

(https://farm5.staticflickr.com/4357/36372530663_74a814a05d_z.jpg)

Offered up to the frame to check the fit and angle, still to be confirmed and welded tomorrow:


As the rear brake is cable operated, originally the cable would have sat down into a boss and was lock wired into place. Luckily a good friend of mine has found an original cable that I can borrow! So I thought I better get on and get the bosses made so that they can be welded onto the rearset plates. I had drawn the part up in CAD and produced a drawing, so over to a mate for machining previously on this thread.

The original cable:

(https://farm5.staticflickr.com/4381/36789106820_4e412c09da_z.jpg)

As the part is relatively simple the machining process can all be done on the 4th axis from a piece of standard barstock in one operation with no need to reposition the workpiece. Then these can be cut-off and then drilled from the back just to finish them off!

(https://farm5.staticflickr.com/4422/36350002384_179d75768e_z.jpg)

(https://farm5.staticflickr.com/4391/36372530323_826405262a_z.jpg)

De-burred and ready to go!

(https://farm5.staticflickr.com/4347/37014843662_e63339e2b8_z.jpg)

Chuffed with how this detail has come out  :D especially the hole for the lockwire!

Frame mods still to do:
- Lower frame tabs for the fairing.
- Oiltank mounts.
- Gear shaft changover kit bush.
- Repair frame tube where the rear brake tube was removed.
- Seat and tank hooks to be added to the brace

Another day of it tomorrow, hopefully will get most of the welding finished off on the frame.

Cheers!
CR21

Title: Re: CR750 replica build
Post by: yozzer74 on January 06, 2017, 12:01:32 AM
Loving this build
Title: Re: CR750 replica build
Post by: paul G on January 06, 2017, 08:11:08 AM
Loving this build

Me too detail is superb  ;D
Title: Re: CR750 replica build
Post by: CR21 on January 06, 2017, 08:23:01 PM
So progress from today:

Seat/tank brace:

It took a while to position this piece around the frame tubes neatly   :-\ And then I remembered after speaking to a previous CR750 builder that I needed to add a breather hole through the brace to accept the crankcase oil breather line. So out the brace came, breather hole installed and back in, jigged up and welded:

(https://farm5.staticflickr.com/4363/37186732645_a7ff263fb4_z.jpg)

(https://farm5.staticflickr.com/4439/36789215430_e311594885_z.jpg)

I still need to add the tank strap hook as well as the seat hooks to the brace.

I bought a spare top yoke in order to see if I could convert a standard CB750K item to look more like the CR750 part. I was unsure of two things, the strength with the cast handlebar bosses removed and how the holes could be filled neatly. Anyway to cut a long story short, I cut the boss off with the bandsaw, linished and shaped the yoke surface, drilled out the threads to remove contaminants, filled the holes with rod. Then this was welded up and linished back!

(https://farm5.staticflickr.com/4414/36789215990_cc781aaff4_z.jpg)

(https://farm5.staticflickr.com/4380/36789215870_eb82d15f1c_z.jpg)

(https://farm5.staticflickr.com/4366/36789215760_00abeda50c_z.jpg)

(https://farm5.staticflickr.com/4419/36789215150_015c0d0434_z.jpg)


 I am relatively happy with the result, it still needs a fair bit of fettling here and there to smooth out the surface but I think it will be alright when finished. Luckily the die cast material welded really well  ;D


Rearsets:

Braced up ready to weld:

(https://farm5.staticflickr.com/4387/36350131294_bcd6f077e1_z.jpg)

(https://farm5.staticflickr.com/4422/36789215610_61996db47f_z.jpg)

(https://farm5.staticflickr.com/4433/37186732435_f5b87ab45f_z.jpg)


As the rearset is effectively 'sealed' a hole was drilled to stop outgassing spoiling the last part of the weld:

(https://farm5.staticflickr.com/4392/36789215030_e81d0c3a45_z.jpg)

The front fairing spigot was also welded up and tacked to the frame to kick off the fairing fitting:

(https://farm5.staticflickr.com/4394/37186732385_d21664bc31_z.jpg)

Also as a little side job, the oil tank is hung from the top with an original honda lined bush. These fix onto threaded bosses on the frame, I was going to turn these from solid bar however they looked a bit heavy, so I turned the back off of each one to thin them down.

(https://farm5.staticflickr.com/4388/36789214960_a84f881d24_z.jpg)

(https://farm5.staticflickr.com/4416/36789215530_d07ed8a2ac_z.jpg)

Fitting of the fairing, oil tank and other frame items will happen in a future fabrication session. Just got to fettle the yoke and fit the fueltank tank strap hook in place tomorrow and then I will start to build up the front end with the double disks! 

Cheers,
CR21
Title: Re: CR750 replica build
Post by: MCTID on January 06, 2017, 09:51:50 PM
I have to say Scott - as an ex Welding/ Radiographic Inspector and CNC Machine Shop Inspector - that I am mightily impressed with your Project.

It's been a pleasure to see how you are progressing and I can't wait to see the final product.

Keep up the good work - and please keep those photos coming............CR Porn no less....LOL.


Title: Re: CR750 replica build
Post by: mike the bike on January 06, 2017, 10:01:04 PM
I'm enjoying this thread as well, can wait for the next exciting episode.  You're probably the only one of us doing anything at the moment.
Title: Re: CR750 replica build
Post by: CR21 on January 07, 2017, 08:46:12 AM
Thanks guys! As I have said before, of course I would not be at this point without the help of some great friends and acquaintances whose knowledge and skills bank is simply inspiring! Of course I have picked up a lot from the forum as well  :D

Cheers
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on January 07, 2017, 10:16:40 AM
I'm saying nothing, 😄 Actually I will, it's excellent, unfortunately it makes mine look like what it is a cheap lookalike! 😄
Title: Re: CR750 replica build
Post by: philward on January 07, 2017, 02:22:11 PM
I'm saying nothing, 😄 Actually I will, it's excellent, unfortunately it makes mine look like what it is a cheap lookalike! 😄
Me too Mark - but I am only building my CR with a hammer, drill and bench vice! Great build though!

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: royhall on January 07, 2017, 02:45:50 PM
I'm enjoying this thread as well, can wait for the next exciting episode.  You're probably the only one of us doing anything at the moment.
Ive got plenty on Mike just not Honda. I would put it on here but as its a Triumph special, probably not. And just to add another comment, what a great build well done.
Title: Re: CR750 replica build
Post by: MarkCR750 on January 07, 2017, 02:53:10 PM
I'm saying nothing, 😄 Actually I will, it's excellent, unfortunately it makes mine look like what it is a cheap lookalike! 😄
Me too Mark - but I am only building my CR with a hammer, drill and bench vice! Great build though!

Sent from my MotoG3 using Tapatalk

That's 2 more tools than I used!😄
Title: Re: CR750 replica build
Post by: onethumb on January 07, 2017, 11:28:26 PM
Embarrassed by the quality. Good work.


Sent from my iPad using Tapatalk
Title: Re: CR750 replica build
Post by: CR21 on January 09, 2017, 12:15:36 AM
Cheers for the comments guys  ;)

Just a quick update on the build. The recent session has now come to an end as I am back to work ;D. I loosely through the rolling chassis back together to get an idea of how the bike is starting to look, some quick images below. Obviously, the forks are sitting high due to the lack of weight...

(https://farm5.staticflickr.com/4385/36997197266_4b65e615f6_z.jpg)

(https://farm5.staticflickr.com/4335/36789439130_38508aab81_z.jpg)

A starting point for the front dash and fairing bracket:

(https://farm5.staticflickr.com/4392/36997197146_c00aa8e08e_z.jpg)


Pleased with how this footpeg is sitting with the 'correct' bolt:

(https://farm5.staticflickr.com/4351/36350355954_52e7cd2483_z.jpg)

This HONDA oil cooler may be a good starting point. I will have to re-work the inlet/outlets though to look more standard:

(https://farm5.staticflickr.com/4367/36789438920_99e5f665f7_z.jpg)


Back to the research and planning for the next building phase,

Cheers
CR21
Title: Re: CR750 replica build
Post by: CR21 on January 19, 2017, 08:20:24 PM
Tiny update regarding the fuel cap ;)

There is much talk around the CR750 fuel filler cap. Here is my interpretation of the situation around the fuelcaps:

The original three Daytona bikes were fitted with magnesium filler caps, to save weight. Many of the factory CR parts were cast from magnesium. Replica magnesium caps are available, but at a price of 400  :o

The kit bikes that were available from Honda, supposedly had the same chrome cap as the CB400 CB500 CB550 CB750 SL350 street bikes.

To cut a long and not very interesting story short, the plan is to use a CB750 fuel cap. Luckily the fuel caps and latch are still available from Honda  :D.

So I had to find a bezel, I placed an advert on the SOHC forum for a rotten/crashed tank that was not worth repairing and came up lucky! I have drawn the bezel up, so may get one machined from stainless or aluminum but I have not decided yet:

(https://farm5.staticflickr.com/4386/36350400814_17b49e2c88_z.jpg)


(https://farm5.staticflickr.com/4435/36350400994_b38749f2ae_z.jpg)

This/a replacement bezel will be bonded onto the filler neck of the aluminum tank to replace the Monza cap.

Plans for this weekend: sort out the double disk fitment  ;)

Cheers!
CR21
Title: Re: CR750 replica build
Post by: philward on January 19, 2017, 08:43:00 PM
Scott, I'm on the double disc adaptation tomorrow - mines the later fork legs so will be slightly different to the early legs on yours
Title: Re: CR750 replica build
Post by: CR21 on January 19, 2017, 10:38:46 PM
I'm on the double disc adaptation tomorrow - mines the later fork legs so will be slightly different to the early legs on yours

Nice  ;D How are you dealing with the speedo-drive collar? I was thinking of machining one up to fit when both disks are fitted?

Cheers
CR21
Title: Re: CR750 replica build
Post by: philward on January 19, 2017, 10:46:43 PM
I'm going to look at it tomorrow - was speaking to Simon Tappin (just ordered exhausts!) and he made up a spacer - I intend to use some tube as a mock up then have a spacer made - it will be trial and error in conjunction with previously posted guide's

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: CR21 on January 19, 2017, 10:48:06 PM
I'm going to look at it tomorrow - was speaking to Simon Tappin (just ordered exhausts!) and he made up a spacer - I intend to use some tube as a mock up then have a spacer made - it will be trial and error in conjunction with previously posted guide's

Sent from my MotoG3 using Tapatalk

Exciting  ;D
Title: Re: CR750 replica build
Post by: philward on January 20, 2017, 06:07:42 PM
Twin discs done! Nothing like the previously posted guide's (worryingly!) - done away with speedo gear and made a spacer to locate replace speedo bits. Main issues that have been previously seen as an issue, lining brake arm parallel to disc which normally requires filing of bottom pivot arm - I had to shim it to get arm parallel! (And shim upper m6 mount's about 5 mm). Both discs are parallel to discs but won't know if all works properly until all hydraulics connected (no where near that point). I'll now have some proper spacers made up from stainless

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: MarkCR750 on January 20, 2017, 07:06:15 PM
Well if the arms are parallel to the discs and the callipers with pads fitted fit and the wheel rotates it should be fine, before I fitted the callipers I put a 12" steel rule edge on across the calliper mounting face on the arms and down across the discs, then measured the gap between the edge of the rule to the disc altering the shims until the gap was parallel across the disc, I had to file the bottom bolt mounting lug on mine, anyway there are bound to be differences between bikes so if it's all parallel sounds like the jobs a good un!.
Title: Re: CR750 replica build
Post by: philward on January 20, 2017, 07:27:17 PM
Only minor issue I have is the new pad that goes on the arm side is a lot thicker and pushes the arm out of parallel so I swapped it to the other side and the new pad from the other side is a few mm thinner fitted in the RH side fine and allowed parallel. The LH now binds slightly (pushing arm slightly out of parallel) and so a mate is going to mill the thicker pad down to the same size as the thinner one. The pads are different makes so don't know why they are different thickness'. The pads surface to the red max wear line is smaller on one set.
I'm glad it's not a use everyday bike as its going to be a pain to take the wheel off!
Title: Re: CR750 replica build
Post by: MarkCR750 on January 21, 2017, 01:59:41 PM
Yes it's annoying having to take the 2 calliper bolts out to remove the calliper every time you need to remove the front wheel, only a problem during build though, I don't think my front wheels been out again for at least 18 months, so barring a puncture it's a small price to pay for brakes that actually work! 😄
Title: Re: CR750 replica build
Post by: CR21 on February 07, 2017, 03:02:54 PM
Just a quick update:

This will allow me to fit disks to both sides of the hub whilst retaining the speedo drive unit without the need to modify any other parts. The machined part will replace the original two part pressing which can't be used as it locates in an area that the disk.

Designed up in CAD, now to draw and then machine:

(https://farm5.staticflickr.com/4415/36350589714_73c72428b9_z.jpg)


(https://farm5.staticflickr.com/4434/37187260235_e41245ca6c_z.jpg)

Some progress on the replica hinged clip-on parts:

(https://farm5.staticflickr.com/4394/37187260355_157f1611e7_z.jpg)

(https://farm5.staticflickr.com/4331/37187259795_e755a37f09_z.jpg)

More to come (hopefully) soon!

Cheers
CR21
Title: Re: CR750 replica build
Post by: Johnwebley on February 07, 2017, 06:24:29 PM
Bloody hell,that is some machining !!


    keep up the good work
Title: Re: CR750 replica build
Post by: captaink on February 27, 2017, 05:02:46 PM
Hi CR21,
Nice work so far,
I'm building my CR replica here in the UK.
Had a bit of a break but I'm back on it now.
I have the Asa Moyce tanks as well, they are nice bits of work...worth the wait.
Do you know what type of fuel tap works with that tank, I have been told its from a Honda motorcross but cant seem to track one down.
Also what are you thinking of doing for a front mudguard / fender.
Regards Keith
Title: Re: CR750 replica build
Post by: haynes66 on February 27, 2017, 05:06:26 PM
welcome back, captaink! i was wondering how the rickman was coming along.
Title: Re: CR750 replica build
Post by: philward on February 27, 2017, 05:17:48 PM
The fuel tap that Meadspead advised me was from a CR250 motocrosser - I got one from an Australian seller (http://www.ebay.co.uk/itm/HONDA-CR250-80-07-GXMOTOR-FUEL-TAP-PETROL-TANK-PETCOCK-/141756762924?hash=item21015c8b2c:g:Yj0AAOSwTapV3XhE). The original is a twin exit tap but you will have to search the .net site for that - don't know if they are available (H2eric on the ,net site got hold of one I seem to remember when reading a thread) - depends how for you want to go.
Its not a priority at the moment for me but the Bartel (Asa Moyce) tanks tap flange bolt holes are not 'blind' and so will need some effective thread sealing to prevent leakage via the thread on the bolts
Phil
Title: Re: CR750 replica build
Post by: captaink on March 01, 2017, 03:57:45 PM


The Rickman engine is complete and I plan to put it in the frame in a week or so.

I've done a bit on the CR in the last few weeks
I purchased another 1977 engine and stripped it to the bones, this has now been aqua cleaned and after accessing the work required I'll be sending it up to the engine man for machining.
The present thought is inspect crankshaft and either polish journals or regrind, new shells for the crank and rods.
As before I have got a big bore kit 836cc and it will be rebored to suit.
Head will have new APE valve guides, valves and springs.
APE casing and cylinder studs.
I also purchased another set of casings, cylinder, head and rocker cover to use as a dummy which will allow me to carry on with the project whilst the engine man Dave from D & M Engineering is doing the machine work.
Pictures show the clean but dummy engine.

Title: Re: CR750 replica build
Post by: Bryanj on March 01, 2017, 05:05:57 PM
Nobody makes undersize shells so regrind don't work
Title: Re: CR750 replica build
Post by: Tomb on March 02, 2017, 07:34:45 AM
Bryan have you Capt'Ks list of bikes? must half a million quid there alone, if you have the money you can get anything done. ;)

I once bored out a Royal Enfield conrod to take different shells, they came from an Austin Allegro that were 10 thou smaller ID to fit an undersize reground crank. It ran for years like that. As you can tell by the Allegro parts it was a looooong time ago.

Nice work Capt'K, no disrespect intended.
Title: Re: CR750 replica build
Post by: Bryanj on March 02, 2017, 02:16:34 PM
If you have the time and cash anything is possible but for us mortals it just ain't so, I did convert a pair of triumph white metalled rods from a 500 to shells but the customer didn't like the cost, from memory £25 in the late 70's
Title: Re: CR750 replica build
Post by: hairygit on March 02, 2017, 04:02:25 PM
Send it to S.E.P. in Kegworth, they build the crank up with submerged argon arc welding then regrind back to original spec. Can vouch for their quality of work.
Title: Re: CR750 replica build
Post by: MarkCR750 on March 02, 2017, 08:27:11 PM
Quote
"Bryan have you Capt'Ks list of bikes? must half a million quid there alone"

I don't think the value is anywhere near half a million, I've totted the bikes up and struggled to reach 464,000 😄, on a serious note though I too can vouch for SEP, you don't have to be in a hurry though because they are very very busy!.

(PS capt'K please will you be my friend?).
Title: Re: CR750 replica build
Post by: captaink on March 05, 2017, 05:58:54 AM
Hi Mark,
I would be your friend but someone as mad as to "Almost " mask up his kitchen to paint his bike bits is some kind of nutter  ;D ;D ;D ;)
I must admit though I did used to put the high temp painted cylinders for the older bikes in the oven to bake them, it makes the oven smell but does the job. And yes she had gone out shopping.
When I was much younger ( late 1970's ) I spray painted my car in the street, tried not to get overspray on the neighbours cars !  " those were the days " 8)

Title: Re: CR750 replica build
Post by: MarkCR750 on March 05, 2017, 08:25:35 AM
Fair enough capn'K I can understand that behaviour being off putting, although in some quarters it has almost given me hero status  :)
PS I'm guessing that a side benefit of spray painting your car in the street was that it simultaneously  marked out your parking bay?.
Title: Re: CR750 replica build
Post by: CR21 on March 16, 2017, 08:57:11 AM
Hello all!

I have been off the forum for a while, but progress is happening on the build. Clip on bosses are completely machined now as are the rear set pinch bolts and front wheel speedo drive plates.

Captaink - your build looks great please keep updating your thread  ;D

With regards to fueltaps - the CR250 taps that fit the bartel tanks are still available from Honda. I am considering machining my own tap, but at the moment I have bigger things to progress on with the frame!

Update to come soon on the clip on bars/front end. Need to start thinking about designing and machining a splitter for the front brakes lines as well. 

Cheers!
CR21
Title: Re: CR750 replica build
Post by: CR21 on March 21, 2017, 11:26:28 AM
Just a quick update:

Speedo drive adapter plate machined:

(https://farm5.staticflickr.com/4363/37187325715_73f264a909_z.jpg)

(https://farm5.staticflickr.com/4383/36373248223_e328df2ae8_z.jpg)

And the filler cap bezel to accept the 'correct' fuelcap:

(https://farm5.staticflickr.com/4399/36373248093_ff348d3028_z.jpg)

(https://farm5.staticflickr.com/4434/36373248373_cd85b52a54_z.jpg)

More to come at the weekend, hopefully front wheel assembly and some movement on the clip-ons!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: paul G on March 21, 2017, 12:28:42 PM
Everything about this build is impressive  ;D
P.S. Can you do me some rear sets for a Z650 ;)
Title: Re: CR750 replica build
Post by: CR21 on March 21, 2017, 12:31:32 PM
Everything about this build is impressive  ;D
P.S. Can you do me some rear sets for a Z650 ;)

Paul anything is possible - send me a message and we can go from there  :)
Title: Re: CR750 replica build
Post by: JamesH on March 21, 2017, 04:23:24 PM
Stunning work (as always). This is going to be special...
Title: Re: CR750 replica build
Post by: CR21 on March 22, 2017, 08:50:38 PM
Cheers James!

Seat, currently being made and shipped over to me. Beautiful attention to detail on this part, the 'studs' heat moulding on the seat and profile are spot on, I could not resist  :D At least this will allow me to finish the seat and tank mountings in one hit:

(https://farm5.staticflickr.com/4368/36350669524_c6db4323a4_z.jpg)

(https://farm5.staticflickr.com/4369/36789788840_070295bd68_z.jpg)

Cheers
CR21

Title: Re: CR750 replica build
Post by: CR21 on March 28, 2017, 01:08:17 PM
Not as much done as the weekend as expected however, I am pleased with how the clamps turned out just got to work out the tubing interface now and the clearance of the master cylinder etc in order to get that right and repeatable I think I will build a jig.

(https://farm5.staticflickr.com/4432/36997538126_e57d675cfa_z.jpg)

(https://farm5.staticflickr.com/4374/36789826590_cf384eb4cd_z.jpg)

Also the speedo drive adapter plate fits nicely:

(https://farm5.staticflickr.com/4427/36997537836_6e120c3c33_z.jpg)

Hoping to have a good session next month to finish the seat/tank mountings on and progress with the front brake etc.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: captaink on March 28, 2017, 06:06:44 PM
Nice bit of machine work mate.
looking good  ;)
Title: Re: CR750 replica build
Post by: CR21 on April 16, 2017, 09:17:29 AM
Quick update:

Speedo adapter plate sitting in place nicely  ;) Front end fitted with double disks. Really easy 'upgrade' as the fork lowers have bosses, it is just a matter of sourcing a 'mirrored' bracket, disk, caliper and carrying arm and bolting it on along with the modded speedo plate.

(https://farm5.staticflickr.com/4353/36790066950_8ddb383755_z.jpg)

(https://farm5.staticflickr.com/4438/36790067070_6c54dab946_z.jpg)

I still need to work out the hole drilling and skimming of these disks, and reevaluate whether they need shimming or not. I have read on a couple of forums that the set-up that I have done needs shimming, however as the caliper arms sit at the moment they are parallel to the disk, and I believe that they should function as intended.

To complete the 'front end brake set-up' I need to do the following:

- Create replica splitter block, cables to the lower calipers.
- Cable to the GL1000 master cylinder, with the mirror mount removed, or David silver can supply a very reasonably priced reproduction master cylinder which is suitable to drive twin calipers.

The 'original' bikes had a splitter attached to the horn mount, like below:

(https://farm5.staticflickr.com/4410/36790066850_0900f43650_z.jpg)

I need to look into thread types and spacing if I were to go down this route.

Another concern of mine is these original forks, obviously, my fork stanchions are only suitable for the bin, due to the corrosion at the top. These original forks are very crude and have been named 'pogo sticks' by other builders! A solution to this would be to have the lowers fitted with cartridges and then run reproduction uprated stanchions. It is of course also an option to go down the GL1000 front end, but I was not too keen on this.

Then, of course, it is building up the front wheel. I already have rims, but need to source spokes and need to skim the ribs off of the front hub to replicate the original cotton reel look that the original magnesium part had. I will have the hub vapour blasted and vibratory-polished to try and represent the original 'new cast' finish.

And of course the replica front mudguard, which is a small project in itself! I am planning on making one from an aluminum blade and fabricating the stays - a job for another time!

Extremely pleased with the seat unit, placed this onto the bike yesterday. I need to do the rear frame cutting, cross brace and hoop to accept this seat, and of course the brackets for the catch tank.

(https://farm5.staticflickr.com/4423/36790066700_302577177b_z.jpg)

Lots to do, but glad the front end is underway!

Cheers!
CR21
Title: Re: CR750 replica build
Post by: captaink on April 17, 2017, 06:09:29 PM
Hi, I went down the GL1000 front end, twin disks etc.
I got a billet top tree from the states and powder coated black.
I got from Silvers a GL1000 master cylinder which can branch off to a splitter or as is fitted to my other CR bike a twin banjo at the master cylinder with a brake line to each calliper.
That front mudguard will be a challenge and I've yet to consider the options.. I'll be watching what you do as your trying to be as accurate as possible.

Your looking good though
Title: Re: CR750 replica build
Post by: CR21 on April 20, 2017, 09:51:53 PM
Hi Captaink, thanks for the reply. Your build is great! Is the GL1000 front end heavy? Do you have any images of your splitter?

Yes the front mudguard is a detail that I really want to get 'right' not an easy one really though... Ideally I don't want to use fibreglass as well...

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on April 24, 2017, 10:16:45 PM
Quick update:

Went to Stafford on Saturday to meet up with people and exchange parts at the show! Usually I don't go to the April show, however I knew that a CR750 guru was going to be there. A bit quiet on the jap front as expected, this was a nice machine:

(https://farm5.staticflickr.com/4415/36997853796_ef35870fb8_z.jpg)

Picked up a lovely CR clutch lever and cable:

(https://farm5.staticflickr.com/4387/36350985004_57ec17fbe0_z.jpg)

And also saw some extremely rare CR parts, the original TLS rear racing hub, as well as a single leading shoe racing hub. All genuine Honda parts cast in Magnesium:


(https://farm5.staticflickr.com/4391/36350985164_b1ee5a7b2c_z.jpg)

(https://farm5.staticflickr.com/4382/36997853336_59b8461e06_z.jpg)


My next thoughts is how can I go about replicating this hub, and a large chunk of aluminium comes to mind...

Cheers
CR21
Title: Re: CR750 replica build
Post by: captaink on May 01, 2017, 01:08:57 PM
Now that would be a challenge a complete hub !  ???

I haven't made a brake splitter as yet, with your machining skills though that should be an easy one for you.
Honda sounds nice, my other CR Replica sounds like that, needs to tick over at 4000 rpm though, a mate of mine says he will take it round Brands for me, but he is an ex BSB rider with no fear.

Regards Keith
Title: Re: CR750 replica build
Post by: CR21 on May 02, 2017, 11:13:01 AM
Now that would be a challenge a complete hub !  ???

I haven't made a brake splitter as yet, with your machining skills though that should be an easy one for you.
Honda sounds nice, my other CR Replica sounds like that, needs to tick over at 4000 rpm though, a mate of mine says he will take it round Brands for me, but he is an ex BSB rider with no fear.

Regards Keith

Hi Keith,

It sure would be, that Is what I am aiming for... Nice!

Cheers
CR21
Title: Re: CR750 replica build
Post by: CR21 on May 05, 2017, 07:44:34 PM
Quick update from today:

Spent most of today pondering about an oil tank  ::) ::) I must say it is certainly a challenge to get this thing in a sensible place!! The alignment is dependent on the breather routing, frame brackets and spacing, as well as the seat. Also the tank does not have any flat surfaces so that helps a lot  ;D ;D

Anyway, progress in images, added the frame brace, cut the frame at the back ready to accept the repositioned seat brace and new hoop. Tank in situ ready for some more thinking and lugging tomorrow  ;)

(https://farm5.staticflickr.com/4383/36790166140_94f06f9776_z.jpg)

(https://farm5.staticflickr.com/4358/36790166000_bfc8a0e900_z.jpg)

(https://farm5.staticflickr.com/4378/36997922246_c7614e3dbd_z.jpg)

(https://farm5.staticflickr.com/4411/36790165650_d60aba97fd_z.jpg)

(https://farm5.staticflickr.com/4360/36790165700_27f443c33a_z.jpg)

(https://farm5.staticflickr.com/4403/36790165690_99e0430147_z.jpg)

Cheers
CR21
Title: Re: CR750 replica build
Post by: philward on May 05, 2017, 08:01:11 PM
Oil tank mounting has been my biggest challenge too Scott - still not 100% happy but its staying where it is now!
Title: Re: CR750 replica build
Post by: CR21 on May 06, 2017, 11:10:42 PM
Phil - it has certainly been fiddly!!

A bit more progress from today:

Knocked up some hanger brackets and spigots, turned bosses for the rubbers to sit on, with a simple folded bracket; these accept an original Honda rubber mounting. Tacked in place for now to check the wheel clearance and hose runs at a later date. The lower brackets are still on the list!

(https://farm5.staticflickr.com/4402/36790315510_759d2d05b2_z.jpg)

(https://farm5.staticflickr.com/4373/37016045552_9e4e6616e6_z.jpg)

Trimmed the rear brace from the frame offcut, this will be repositioned and lowered on the frame, the original Honda pressing was pretty poor so I took the chance to straighten the edge before it goes back on:

(https://farm5.staticflickr.com/4429/36790315460_b93a0ddc0a_z.jpg)

(https://farm5.staticflickr.com/4440/36790315380_92c26c53ce_z.jpg)

Folded up the rear tank strap mounting, I wanted to get a fair bit of stretch on the rubber to keep it strong on the mountings, having the double fold in the bracket provides more strength for the weld area. 

(https://farm5.staticflickr.com/4372/36351128884_13136709a7_z.jpg)

(https://farm5.staticflickr.com/4425/36373901203_a939b22414_z.jpg)

(https://farm5.staticflickr.com/4352/36790315320_8f16bba399_z.jpg)

Onto the rear brake pedal. I bought a rough casting of an original brake pedal, this needed a lot of cleaning up and a bush pressing into it. The casting quality is not great, but probably reflects the era. Set up the pedal in the mill and skimmed the gate off of the casting, as well as facing off both of the bushing faces. Hole bored slightly undersized for an interference fit, heated the pedal to around 100 degrees and then pressed in the bush.

(https://farm5.staticflickr.com/4411/37016045432_d64bbb040f_z.jpg)

More heat needed!!

(https://farm5.staticflickr.com/4441/36373901843_534ab4d130_z.jpg)

Pressed into place, lots of tidying up of the rough casting to be done:

(https://farm5.staticflickr.com/4392/36351129004_5912d87783_z.jpg)

Took the triple tree off and extended the lock stops.

That is all for now! The seat mounts I will machine up to get those smart as they will be difficult to fabricate from sheet material due to the tight double folds. Still got to do the following to the frame:

- Mirrored horn bracket for the oil cooler mount.
- Seat mounts and rear hoop with repositioned frame brace.
- Fit fairing and confirm front spigot location and angle.
- Lower oil tank mounts.
- Look into oil tank breather routing and catch tank.

Cheers
CR21
Title: Re: CR750 replica build
Post by: philward on May 07, 2017, 09:30:27 AM
Looking good Scott. Ref the mirrored horn mounting for the oil cooler - after I mounted the mirrored bracket, I had to make another bracket/plate to lower the cooler to avoid the cooler's exit's pointing at the side of the tank
Phil

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: CR21 on May 07, 2017, 10:01:50 AM
Looking good Scott. Ref the mirrored horn mounting for the oil cooler - after I mounted the mirrored bracket, I had to make another bracket/plate to lower the cooler to avoid the cooler's exit's pointing at the side of the tank
Phil

Sent from my MotoG3 using Tapatalk

Cheers Phil!
Title: Re: CR750 replica build
Post by: JamesH on May 07, 2017, 10:10:04 AM
Excellent work as always. Really enjoying seeing this come together. If you're considering going the DID alloy rim route drop me a PM. I have a few 3.5 x 18" DID alloy rims I've collected over the years and they look great with the GL1000 front 19" alloy DID rim. James
Title: Re: CR750 replica build
Post by: CR21 on May 08, 2017, 08:23:15 AM
Excellent work as always. Really enjoying seeing this come together. If you're considering going the DID alloy rim route drop me a PM. I have a few 3.5 x 18" DID alloy rims I've collected over the years and they look great with the GL1000 front 19" alloy DID rim. James

Thanks James, I will bare that in mind,
Cheers,
CR21
Title: Re: CR750 replica build
Post by: paul G on May 08, 2017, 02:05:14 PM
Love this build ;D
Title: Re: CR750 replica build
Post by: CR21 on September 13, 2017, 12:24:49 PM
Just updated all of the broken links on this thread! Sorry about that  ::)
Title: Re: CR750 replica build
Post by: CR21 on September 13, 2017, 12:25:03 PM
Not posted on this thread for a while as I have been super busy, and also the 'top secret' Yamaha that I am working on is consuming a lot of my time, but its fun  ;)

Few small replica fixings sorted for the CR, plus a couple of spares of course:

Replica bolts for the master cylinder and the clutch bracket, with the very small lock wire holes!

(https://farm5.staticflickr.com/4400/35678954673_e293a77fed_z.jpg)

(https://farm5.staticflickr.com/4334/36319071672_122d350873_z.jpg)

Bushings done for the rear brake pedal:

(https://farm5.staticflickr.com/4366/36349811571_3869b85d75_z.jpg)

(https://farm5.staticflickr.com/4340/36349801381_007418df5e_z.jpg)

Other miscellaneous bolts for various locations:

(https://farm5.staticflickr.com/4365/35652245954_f1664fe3dd_z.jpg)

That is all for now, working away on a few details for this CR so it's all coming along just not as the usual pace :)

Also I need to get around to updating the links on this thread, it will happen soon  ::)

Cheers
CR21
Title: Re: CR750 replica build
Post by: CR21 on September 13, 2017, 12:25:24 PM
Just a quick update:

Had a fantastic time at the classic TT/MGP. There was a CR750 replica in the parade with a few trick bits on so I spent a while taking reference pictures of that. It sounded really rather nice going past the Conkerfields!

I believe that this bike is a replica, but it does have some genuine works bits on! Really handy as a reference  ;)

Me taking thousands of photographs as per usual:

(https://farm5.staticflickr.com/4377/36158140993_a2489ab52f_z.jpg)

(https://farm5.staticflickr.com/4434/36570523760_086bf958c6_z.jpg)

Cheers
Cr21
Title: Re: CR750 replica build
Post by: CR21 on September 13, 2017, 12:25:51 PM
Quick update!

I have been super busy on the Yamaha project, but I have been working on a few small bits for the CR:

I have been working on a few small details, after seeing the CR750 over at the Manx, I decided that a custom throttle was in need. A dual-action push and pull throttle housing which looks "original" with the correct fastenings and adjusters. I have modelled this up in CAD, and will post some images shortly. I will most probably utilise an original or new throttle tube and will machine the other parts.

I have also been playing with the front brake splitter, this will be held on with a wire clip and a steel plate bracket. The T will be machined from solid aluminium, and the bracket and wire will be fabricated.

(https://farm5.staticflickr.com/4363/37059217581_2d875af116_z.jpg)

Another small detail is the works style fuel tap. Managed to get a starting point CAD model online, and to be honest the original design is pretty rubbish in terms of sealing. I think I will produce a version that looks like the original but has internals that won't leak! The TZ taps were pretty known for leaking as well  :-\

Here is the fuel tap body:


(https://farm5.staticflickr.com/4430/37201376735_176dc92ff4_z.jpg)

(https://farm5.staticflickr.com/4381/37059217481_3b7021b439_z.jpg)


Anyway I wanted to test out some new technology, casting is something that has always fascinated me, I think it's the history around the process, and how good it can be as a production method. Loss wax casting, is where a wax model or plug is made of the intended shape, this is buried in sand or plaster with a vent and a sprue. When the molten aluminium is poured into the sprue hole the wax melts away allowing the aluminium to fill the cavity. This is a common method of casting relatively low volume parts.

However the difficulty and repeatability issues come when producing the plug from wax as you need a mould to create this plug.

3D printing technologies are moving on at quite a pace, and it's something that I am involved with on a daily basis, both designing and having parts 3D printed. A new material has recently been released which is a "castable" resin so I thought I would give it a try!

Here is the part as it has come out of the printer, you can see a "raft" the 2D shape on the table, and the "supports" the random pillars holding the object up. The raft and supports are removed leaving the plug.


(https://farm5.staticflickr.com/4387/37201376815_3c899cc4de_z.jpg)

(https://farm5.staticflickr.com/4426/37059217821_ecfb481729_z.jpg)

The plan is to bury this model in plaster, leaving a vent and a sprue. This can then be cast for, or burnt out and cast from.

Of course after the casting process a lot of the surfaces would have to be post-machined to give suitable surface finishes for sealing and interfacing with other parts. And in reality the cast part would have holes blanked off, however for this stage I am interested to see what resolution is possible to get from a plaster casting.

Progress to come at a later date on the fuel tap front.

I have also made a small amount of progress on the clip-ons: tube interface parts being machined at the moment:

(https://farm5.staticflickr.com/4345/37201376715_02975543bf_z.jpg)

(https://farm5.staticflickr.com/4361/36364342754_144b4670b0_z.jpg)

(https://farm5.staticflickr.com/4410/36803660640_445019b887_z.jpg)

Due to the complex curvature, this part will start off as a piece of EN8 bar, will be CNC turned, and then added to the 4th axis of a Mill to 3D machine the complex geometry.

This enables the tube to be set at a repeatable angle, compared to the boss each time, this also gives a good engagement sleeve for the length of handlebar tube.

Cheers
CR21
Title: Re: CR750 replica build
Post by: CR21 on September 21, 2017, 10:16:47 AM
Quick update:

Tube bosses machined from EN8, ready for welding up:

(https://farm5.staticflickr.com/4398/36551185283_51ace5f951_z.jpg)

Cheers,
CR21
Title: Re: CR750 replica build
Post by: JamesH on September 21, 2017, 11:12:14 AM
Excellent progress as always.

Maybe worth reaching out to Richard (RGP750) if you need any advice on the casting process - he's been doing it as the 'day job' since before I was born ( :-) ). James
Title: Re: CR750 replica build
Post by: CR21 on September 21, 2017, 01:22:35 PM
Excellent progress as always.

Maybe worth reaching out to Richard (RGP750) if you need any advice on the casting process - he's been doing it as the 'day job' since before I was born ( :-) ). James

Hi James,

Thanks for that  :D

Thanks,
Scott
Title: Re: CR750 replica build
Post by: CR21 on September 25, 2017, 05:59:31 PM
Quick update:

Parts together and ready for welding. A quick side-by-side shot with an original HRC part:

(https://farm5.staticflickr.com/4344/37312774181_5656c8bbc9_z.jpg)

(https://farm5.staticflickr.com/4435/37312773411_beef952c2a_z.jpg)

(https://farm5.staticflickr.com/4488/37455492575_cebde00a74_z.jpg)

I think I am going to make a second set of these from a high grade of Aluminium, as soon as I am happy with the design and fit.

Cheers
CR21
Title: Re: CR750 replica build
Post by: Trigger on September 25, 2017, 06:55:23 PM
Nice work, fancy making some new cam towers  ;) Can't find a company that will do a small amount, everyone that has the correct CNC only do large orders.
Title: Re: CR750 replica build
Post by: philward on September 25, 2017, 07:26:42 PM
Nice work, fancy making some new cam towers  ;) Can't find a company that will do a small amount, everyone that has the correct CNC only do large orders.
I'm no expert Graham but in the 90s I had a Phil Read Rep with cam towers that where goosed - had them line bored and had some shells made for bottom of towers and complete new phosy bronze caps made that 'clamped' in the bottom shell's - not standard spec but worked for several thousand miles while I had it - hope that makes sense after several Madererian beers on holiday!

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: CR21 on September 25, 2017, 07:34:39 PM
Nice work, fancy making some new cam towers  ;) Can't find a company that will do a small amount, everyone that has the correct CNC only do large orders.

Sure, drop me a message :)
Title: Re: CR750 replica build
Post by: Trigger on September 25, 2017, 08:28:03 PM
Nice work, fancy making some new cam towers  ;) Can't find a company that will do a small amount, everyone that has the correct CNC only do large orders.
I'm no expert Graham but in the 90s I had a Phil Read Rep with cam towers that where goosed - had them line bored and had some shells made for bottom of towers and complete new phosy bronze caps made that 'clamped' in the bottom shell's - not standard spec but worked for several thousand miles while I had it - hope that makes sense after several Madererian beers on holiday!

Sent from my MotoG3 using Tapatalk

I know this method Phil, but it also weakens the towers. At this time we line bore the towers and metal spray the journals on the cam shaft and then grind to fit. This can only be done it the tower has only had minimum damage. 
Title: Re: CR750 replica build
Post by: philward on September 25, 2017, 08:40:14 PM
That's me told - back to my beer! No seriously, when I did mine, I was able to machine can bearings slightly to get any wear marks out then have them case hardened then machined towers/caps to suit - it's all down to budget I suppose - I was working at BAE at the time and cost nothing! Now back to the Madererian beer!

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: Trigger on September 25, 2017, 08:49:54 PM
That's me told - back to my beer! No seriously, when I did mine, I was able to machine can bearings slightly to get any wear marks out then have them case hardened then machined towers/caps to suit - it's all down to budget I suppose - I was working at BAE at the time and cost nothing! Now back to the Madererian beer!

Sent from my MotoG3 using Tapatalk

How many beers now mate ?
Title: Re: CR750 replica build
Post by: philward on September 25, 2017, 08:56:39 PM
About 6 since 3 ish but now having Madererian meal ( restaurant within all inclusive hotel) - but had a few before that around the pool  - it's a hard life!

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: MCTID on September 25, 2017, 11:07:37 PM
Coral..........splendid Madeiran Lager (multi award winning........I know these things....I'll be there for the 12th time soon). Enjoy. LOL.
Title: Re: CR750 replica build
Post by: CR21 on September 27, 2017, 09:40:04 AM
Quick update:

Parts together and ready for welding. A quick side-by-side shot with an original HRC part:

(https://farm5.staticflickr.com/4344/37312774181_5656c8bbc9_z.jpg)

(https://farm5.staticflickr.com/4435/37312773411_beef952c2a_z.jpg)

(https://farm5.staticflickr.com/4488/37455492575_cebde00a74_z.jpg)

I think I am going to make a second set of these from a high grade of Aluminium, as soon as I am happy with the design and fit.

Cheers
CR21
Title: Re: CR750 replica build
Post by: CR21 on September 27, 2017, 09:40:28 AM
A quick bit of progress on the front brake splitter assembly design:

(https://farm5.staticflickr.com/4369/37300406736_079b1c5eab_b.jpg)

I still need to add some location grooves for the wire clip.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 03, 2017, 02:12:22 PM
Quick update on the clip ons!

My master welder friend has assembled the clip ons :) All good to go now:

(https://farm5.staticflickr.com/4458/23620826048_e8595eafe3_z.jpg)

(https://farm5.staticflickr.com/4448/23620825998_602fc433a0_z.jpg)

(https://farm5.staticflickr.com/4490/36763453484_2583736840_z.jpg)

(https://farm5.staticflickr.com/4498/23620826138_0b9b39552f_z.jpg)

Cheers
CR21
Title: Re: CR750 replica build
Post by: MarkCR750 on October 03, 2017, 05:03:38 PM
Looks really good, this thread is going to be a terrific reference for people currently building or about to build a CR750, keep it up👍
Title: Re: CR750 replica build
Post by: CR21 on October 03, 2017, 05:25:39 PM
Looks really good, this thread is going to be a terrific reference for people currently building or about to build a CR750, keep it up👍

Thanks Mark  :)
Title: Re: CR750 replica build
Post by: JamesH on October 03, 2017, 06:44:23 PM
Awesome...
Title: Re: CR750 replica build
Post by: Johnwebley on October 03, 2017, 08:40:30 PM
the attention to detail,and workmanship is outstanding,

  looking forward to the finished bike running
Title: Re: CR750 replica build
Post by: philward on October 03, 2017, 09:01:28 PM
the attention to detail,and workmanship is outstanding,

  looking forward to the finished bike running
Great work - your setting very high standards Scott!

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: CR21 on October 04, 2017, 08:28:32 AM
Thanks, guys. When I committed to building a replica that was the plan; to build the bike to the highest standard, quality and detail that I can afford. Working away on these small details seems trivial but fingers crossed it will all come together  :)

Cheers
CR21
Title: Re: CR750 replica build
Post by: paul G on October 04, 2017, 12:22:58 PM
Stunning work all the way.
Can't wait to see the finished item :) :)
Title: Re: CR750 replica build
Post by: MarkCR750 on October 04, 2017, 08:25:00 PM
Here's a link to H2erics build, another fine piece of work, if I remember correctly he even had Magnesium sliders made!, could be some useful info in there for you 👍

http://forums.sohc4.net/index.php?topic=94588.0
Title: Re: CR750 replica build
Post by: CR21 on October 05, 2017, 08:02:26 AM
Here's a link to H2erics build, another fine piece of work, if I remember correctly he even had Magnesium sliders made!, could be some useful info in there for you 👍

http://forums.sohc4.net/index.php?topic=94588.0

Hi Mark,

Eric's thread is fantastic, and is a great reference point and source of inspiration! When I started thinking about the build it was this forum and that thread that made my mind up  :) I have been in touch with Eric via PM, a great help  ;D

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 09, 2017, 04:54:16 PM
Quick update:

Repro master cylinder suitable to run the double disk arrived, fitted with the replica bolts, I also dropped the clutch lever on to have a look!

(https://farm5.staticflickr.com/4455/36885846894_00b581a5e4_z.jpg)

(https://farm5.staticflickr.com/4494/36885847314_18be722294_z.jpg)

(https://farm5.staticflickr.com/4461/36926350053_848df027d7_z.jpg)


Got to do the mods to the master cylinder:
- Remove ridges
- Remove mirror mount
- Remove some casting marks
- Replace with a more original looking cap

I will also linish the tube weld back and paint these clip-ons black and finish them with a turned nylon end cap.

I should be picking up some goodies at the weekend for the CR  ;)

Cheers!
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 11, 2017, 01:56:07 PM
Quick update on some very tiny details!

I have been looking for a more period style filler cap for the oil tank. The Monza is pretty and shiny but does not look that original, it is also difficult to open when the seat is in place. After seeing a CR kit bike with a filler cap on that closely resembles the GL1000 fuel cap that is what I have decided to go for:

(https://farm5.staticflickr.com/4444/23781388208_0fdb1349a0_q.jpg)

Once this arrives I will make an aluminium neck to be welded to accept this cap. 


The other thing is the seat fasteners, the ones that came on the seat were not quite right, they looked ok but let down the rest of the seat in my opinion as they are too bulbous:

(https://farm5.staticflickr.com/4500/36924119854_9e219ee9b7_m.jpg)

The Honda seat studs, found on the CB400F do the trick and make the seat look a little less bling as the studs are less polished:

(https://farm5.staticflickr.com/4461/23781388368_587dfee1e5_z.jpg)

It's the small things... :)

Cheers!
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 14, 2017, 09:07:23 PM
Had a good wander around Stafford today! Met up with some good contacts, especially for the Yam project.

Also met up with a CR guru and purchased these bits:

Sand-cast side cover and fuel tap:

(https://farm5.staticflickr.com/4474/37664651002_83b7c8518a_z.jpg)

(https://farm5.staticflickr.com/4463/36986794884_d70f371e8c_z.jpg)

(https://farm5.staticflickr.com/4448/36986809714_94cfd818bd_z.jpg)

(https://farm5.staticflickr.com/4484/37439045670_842e6f4ba2_z.jpg)

(https://farm5.staticflickr.com/4491/37697016321_d2caa63776_z.jpg)


Venhill '888' quick action throttle:

(https://farm5.staticflickr.com/4470/36986805244_153400768c_z.jpg)

The side cover is just a rough casting so needs a lot of loving, however apparently they were pretty poor when supplied new in the kit in the 1970s. I will trim off the gates and sprue, fly cut  a face seal and drill for bolting on. I would like to CNC my own one of these but that will have to go on the back burner for now.

The fuel tap, is ready for bolting on! I am still going to machine one of these though.

And the throttle, its a starting point. I will either run this as-is but stripped of the anodising, vibro-polished add with some period fastenings. Or I am going to make a new throttle as a replica of the original kit style one.

Cheers
CR21
Title: Re: CR750 replica build
Post by: philward on October 14, 2017, 09:11:29 PM
Had a good wander around Stafford today! Met up with some good contacts, especially for the Yam project.

Also met up with a CR guru and purchased these bits:

Sand-cast side cover and fuel tap:

(https://farm5.staticflickr.com/4474/37664651002_83b7c8518a_z.jpg)

(https://farm5.staticflickr.com/4463/36986794884_d70f371e8c_z.jpg)

(https://farm5.staticflickr.com/4448/36986809714_94cfd818bd_z.jpg)

(https://farm5.staticflickr.com/4484/37439045670_842e6f4ba2_z.jpg)

(https://farm5.staticflickr.com/4491/37697016321_d2caa63776_z.jpg)


Venhill '888' quick action throttle:

(https://farm5.staticflickr.com/4470/36986805244_153400768c_z.jpg)

The side cover is just a rough casting so needs a lot of loving, however apparently they were pretty poor when supplied new in the kit in the 1970s. I will trim off the gates and sprue, fly cut  a face seal and drill for bolting on. I would like to CNC my own one of these but that will have to go on the back burner for now.

The fuel tap, is ready for bolting on! I am still going to machine one of these though.

And the throttle, its a starting point. I will either run this as-is but stripped of the anodising, vibro-polished add with some period fastenings. Or I am going to make a new throttle as a replica of the original kit style one.

Cheers
CR21
Who did you get the tap from Scott?

Sent from my MotoG3 using Tapatalk

Title: Re: CR750 replica build
Post by: CR21 on October 14, 2017, 09:14:02 PM
Who did you get the tap from Scott?

Sent from my MotoG3 using Tapatalk

PM sent  :)
Title: Re: CR750 replica build
Post by: CR21 on October 17, 2017, 09:22:09 PM
Hi Kawa, its works and looks well, but I just dont think it looks period enough for the CR...

Anyway, super quick update:

To fit the GL1000 filler cap I need to make up a filler cap bezel to weld to the oiltank. 

(https://farm5.staticflickr.com/4444/23781388208_0fdb1349a0_q.jpg)

Mocked one up in CAD, and sent it to print yesterday:

(https://farm5.staticflickr.com/4464/37091057283_8dcfab3964_z.jpg)

(https://farm5.staticflickr.com/4467/23908269058_e9c6baa521_z.jpg)

The reason for printing this is to test the design against the compression of the spring, before committing to turning/milling one in aluminium. Update on the fit tomorrow!

Cheers
CR21
Title: Re: CR750 replica build
Post by: Bryanj on October 18, 2017, 06:18:08 AM
It arrived OK then?
Title: Re: CR750 replica build
Post by: CR21 on October 18, 2017, 06:53:19 AM
It arrived OK then?

Yes thanks. I sent you an email on Monday  :)
Title: Re: CR750 replica build
Post by: CR21 on November 01, 2017, 09:52:14 AM
A quick update. Some small parts machined up:

Gear changeover bush to hold the olive:

(https://farm5.staticflickr.com/4474/26308397759_405d32005e_c.jpg)

(https://farm5.staticflickr.com/4470/26308398039_cb817a9385_c.jpg)

Seat hooks for welding onto the cross brace:

(https://farm5.staticflickr.com/4479/37375450104_390610fe0d_c.jpg)

Front brake splitter:

(https://farm5.staticflickr.com/4488/38053612392_0e2ac3acfd_c.jpg)


Cheers,
CR21
Title: Re: CR750 replica build
Post by: captaink on November 10, 2017, 02:03:41 PM
Fuel Tap of great interest
may I ask where it comes from ?
Title: Re: CR750 replica build
Post by: CR21 on November 10, 2017, 02:36:19 PM
Fuel Tap of great interest
may I ask where it comes from ?

pm sent :)
Title: Re: CR750 replica build
Post by: SamCR750 on February 08, 2018, 10:09:37 AM
CR21, Phil Ward in Wigan linked me up with this thread and I must say, it made a very interesting read, good luck with getting it up and running.

Sam.  ;)
Title: Re: CR750 replica build
Post by: CR21 on February 08, 2018, 10:15:20 AM
CR21, Phil Ward in Wigan linked me up with this thread and I must say, it made a very interesting read, good luck with getting it up and running.

Sam.  ;)

Hi Sam, thanks!

As a general update - the progress is super slow as I have been absorbed into a very special Yamaha build! However, I am planning on making some progress this year with the aim of completing the rolling chassis.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: SamCR750 on February 08, 2018, 10:41:25 AM
CR21, Phil Ward in Wigan linked me up with this thread and I must say, it made a very interesting read, good luck with getting it up and running.

Sam.  ;)

Hi Sam, thanks!

As a general update - the progress is super slow as I have been absorbed into a very special Yamaha build! However, I am planning on making some progress this year with the aim of completing the rolling chassis.

Cheers,
CR21

No problem mate, some builds take a lot more time than what we thought they would in the first place.
At the moment, I'm involved with a very large project rebuilding two very famous drag bikes from the 70s.
The projects have been on going for just over 6 years now, haha, but the end is looking close to being in sight now.
Would you like to tackle putting this mess back in shape. haha.

Title: Re: CR750 replica build
Post by: CR21 on February 08, 2018, 10:44:43 AM
CR21, Phil Ward in Wigan linked me up with this thread and I must say, it made a very interesting read, good luck with getting it up and running.

Sam.  ;)

Hi Sam, thanks!

As a general update - the progress is super slow as I have been absorbed into a very special Yamaha build! However, I am planning on making some progress this year with the aim of completing the rolling chassis.

Cheers,
CR21

No problem mate, some builds take a lot more time than what we thought they would in the first place.
At the moment, I'm involved with a very large project rebuilding two very famous drag bikes from the 70s.
The projects have been on going for just over 6 years now, haha, but the end is looking close to being in sight now.
Would you like to tackle putting this mess back in shape. haha.

Awesome - yes I would like to tackle that!! Do you have a thread about this?!

It's frustrating, but my goal is classic TT 2020, and that will happen  ;) Just need to finish the Yamaha and two other restorations to be able to find the time first!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: philward on February 08, 2018, 11:31:10 AM
CR21, Phil Ward in Wigan linked me up with this thread and I must say, it made a very interesting read, good luck with getting it up and running.

Sam.  ;)

Hi Sam, thanks!


As a general update - the progress is super slow as I have been absorbed into a very special Yamaha build! However, I am planning on making some progress this year with the aim of completing the rolling chassis.

Cheers,
CR21

No problem mate, some builds take a lot more time than what we thought they would in the first place.
At the moment, I'm involved with a very large project rebuilding two very famous drag bikes from the 70s.
The projects have been on going for just over 6 years now, haha, but the end is looking close to being in sight now.
Would you like to tackle putting this mess back in shape. haha.

Is that THE Russ Collins bike Sam? In this country?
Title: Re: CR750 replica build
Post by: SamCR750 on February 08, 2018, 11:40:17 AM
It is Phil but sadly Russ Senior is no longer with us.
It's his Son Russ Jr that is running the rebuilds but in the States.
He joined my team a few years back and then again last year at the World Finals at Valdosta in South Georgia.
Here's a pic of young Russ with my bike.
Title: Re: CR750 replica build
Post by: SamCR750 on February 08, 2018, 11:46:12 AM
CR21, there are a couple of threads on it but one is on Facebook, I'll dig out links for you, the other one is on sohc4.net.

https://www.facebook.com/groups/451231164982012/

http://forums.sohc4.net/index.php/topic,99452.0.html
Title: Re: CR750 replica build
Post by: SamCR750 on February 08, 2018, 12:41:39 PM
This was all we had to start with for the AT&SF bike.
The complete bike had to be built around the motor unit.
We didn't realize at the time but the motors were in a right mess and all needed complete rebuilds, this is still ongoing as not much of each motor was standard and not all three were the same.
Title: Re: CR750 replica build
Post by: Napoleonb on February 18, 2018, 01:18:03 PM
Hi Scott, your build sure is coming along nicely!
Title: Re: CR750 replica build
Post by: CR21 on February 18, 2018, 04:13:48 PM
Hi, your build sure is coming along nicely!

Thanks Nap, how is yours coming along?!

CR21
Title: Re: CR750 replica build
Post by: Napoleonb on February 18, 2018, 05:15:35 PM
The bike itself isn't progressing much since I've completed it to about 90%.
But I've been able to obtain a dozen or so NOS 970 and 971 items, for most parts I've got some spares so I decided to build a second bike while I'm still at it.
Title: Re: CR750 replica build
Post by: AshimotoK0 on February 18, 2018, 06:20:17 PM
Welcome Nap.. small world ! ...Ash
Title: Re: CR750 replica build
Post by: CR21 on February 27, 2018, 12:53:57 PM
The bike itself isn't progressing much since I've completed it to about 90%.
But I've been able to obtain a dozen or so NOS 970 and 971 items, for most parts I've got some spares so I decided to build a second bike while I'm still at it.

That sounds like a good plan  ;)
Title: Re: CR750 replica build
Post by: CR21 on July 29, 2019, 09:25:51 AM
Digging this project back up after a long time doing other things!

I still have  a huge list of things to do and I am working through this, but it has been handy to have a break in order to properly research some aspects of the build.

A big part of kicking off the project was a chance to see an extremely well done CR750 replica at Mallory Park. This was built by Eric who I got in touch with through this forum. As I am sure many members are aware, the attention to detail on this build is fantastic, the project has taken a long time to get right but was well worth it. It both looks and sounds spectacular. If my bike turns out anything like this I will be very pleased!

(https://live.staticflickr.com/65535/48402359196_3ce2dd71a6_c.jpg)

The weather was a little soggy earlier on in the day when I took the 'detail' images:

(https://live.staticflickr.com/65535/48402492806_e528e54682_c.jpg)

(https://live.staticflickr.com/65535/48402492626_dcee1342d3_c.jpg)

(https://live.staticflickr.com/65535/48402492866_e9bb89950a_c.jpg)

(https://live.staticflickr.com/65535/48402636342_b004a3e477_c.jpg)

(https://live.staticflickr.com/65535/48402493146_970128674b_c.jpg)


Please see the start up video below (sound on!)

https://www.flickr.com/photos/139374148@N06/48402396316/ (https://www.flickr.com/photos/139374148@N06/48402396316/)


I also met another chap who I have been dealing with for a long time during this project, he took along his Honda 750 race bike which is kitted out with many genuine original CR750 honda parts. Including the tank, rear wheel, front hub and carbs.

(https://live.staticflickr.com/65535/48402624977_1ed409c8b6_c.jpg)

(https://live.staticflickr.com/65535/48402481211_ac448cd161_c.jpg)

(https://live.staticflickr.com/65535/48402625312_d38b345a9f_c.jpg)

(https://live.staticflickr.com/65535/48402636867_c71ee38b21_c.jpg)


I also picked up a brand new copy of the October 1970 'Cycle' magazine which I have been searching for for a while.


(https://live.staticflickr.com/65535/48402624842_c3750dea9f_c.jpg)

(https://live.staticflickr.com/65535/48402624697_0b9fe98d46_c.jpg)

(https://live.staticflickr.com/65535/48402624512_c3bc67dba2_c.jpg)

(https://live.staticflickr.com/65535/48402541356_feebb75850_c.jpg)


Hopefully I will be able to provide some more regular updates on various parts of the project soon. I would really like to get a rolling chassis complete this year.

Cheers!
CR21
Title: Re: CR750 replica build
Post by: Laverda Dave on July 29, 2019, 12:06:03 PM
Hi CR21. Good to hear your enthusiasm has returned and it looks like you have some more information progress with the build. Keep the progress photos coming as we all want to follow the build.
Title: Re: CR750 replica build
Post by: Rob62 on July 29, 2019, 01:09:19 PM
The bike looks even better in the flesh and sounds awesome,,, it certainly shook up the café diners when he fired her up on Sunday morning!

Those original CR carbs look very "sand cast"... almost home made  :o
Title: Re: CR750 replica build
Post by: philward on July 29, 2019, 09:30:08 PM
Eric's bike is on another level, the originality is suburb - and Scott's will be I'm sure. Scott and Eric have helped with my build (although my road going CR Rep isn't in the same league!)
Keep the build thread going Scott
Title: Re: CR750 replica build
Post by: CR21 on July 30, 2019, 10:15:58 PM
Thanks for the replies guys!

Rob - it certainly did amazing sound  :) Yes they do look a little home-cast!

Phil - your rep is a lovely bike and you have done it remarkably quickly, its great that we have all met through these builds and have managed to help one another. Thanks Phil with a bit of luck it will turn out alright!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 07, 2019, 10:18:55 PM
Hi all,

I am gathering parts at the moment for a push on the rolling chassis.

I have a week off soon and the plan is to focus on the rolling chassis to progress that along so that I can properly start the dry build.

Hopefully I can kick some life back into this thread!

Oil catch tank:

A little progress on the oil catch tank, this is located underneath the seat of the works CR750.

This is the type of tank I will be replicating:

(https://live.staticflickr.com/65535/48861862057_b19e2f99f8_c.jpg)

Thanks to Eric for the info!

Modelled up in CAD a while ago:

(https://live.staticflickr.com/65535/48861666641_cb70a93ceb_c.jpg)


I ran a 3D print off in a draft resin (quick and cheap! around 2 hrs build time) to check fitment and clearances before fabricating in Aluminium. As the part is going to be made from thin aluminium I thickened the walls for the 3D print and split it into to pieces, for ease of printing:

(https://live.staticflickr.com/65535/48861658261_e0d19442c6_c.jpg)

(https://live.staticflickr.com/65535/48861853827_2660c848cc_c.jpg)

I have seen a few different types of tanks, so will do a little more research before starting!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 13, 2019, 10:33:54 PM
The oil catch tank or 'Sniffer box' as some people call it, is quite the point of controversy across forums!

The one that I drew up and 3D printed was a copy of a copy. This was created over in France by a chap who has built a few replicas, however it does not seem to be as accurate as I originally thought. Another CR guru (thanks if you are reading!) has steered me towards a more correct design, based on some old images and notes from the factory bikes.

It looks a little different now!

Ref image 1

(https://live.staticflickr.com/65535/48864686321_cf42a259af_o.jpg)

Ref image 2

(https://live.staticflickr.com/65535/48864687401_c04bf79b3d_o.jpg)

Apparently two versions of this tank were available.

The side breather/exhaust was apparently what was at Daytona and on the works bikes. I imagine this was to do with the short seat.

(https://live.staticflickr.com/65535/48864686181_51cffdf0bf_o.jpg)

(https://live.staticflickr.com/65535/48864163648_d8bccaa0e9_o.jpg)

And the rear breather on the kit bikes:

(https://live.staticflickr.com/65535/48864686201_a4d3d4b07d_o.jpg)


As I am creating a CR works style bike replicating the Daytona winning bike, I will be going for the side exit catch tank variant. I will probably make up a 'buck' to create the radii on the edges, and roll a piece in the centre to match, then spring bend the inlet/outlets. The original notes show some baffles as well so it would be good to build these in.
 

It is so difficult with these bikes to be 'accurate' as the bikes that were at Daytona were all slightly different, the 'kit' bikes had a variety superseded parts across the years and of course there are a few replicas out there.

Another can of worms is the oil tank brackets  ::)

Cheers,
CR21
Title: Re: CR750 replica build
Post by: Napoleonb on October 15, 2019, 11:36:58 AM
Can't wait to see this part getting shape!
Title: Re: CR750 replica build
Post by: CR21 on October 15, 2019, 03:35:50 PM
Can't wait to see this part getting shape!

Thanks Nap!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 18, 2019, 11:35:47 AM
Quick 3D print of the breather box:

(https://live.staticflickr.com/65535/48918353767_4681dcc71c_c.jpg)

(https://live.staticflickr.com/65535/48918353707_9ec796be27_c.jpg)

This will allow me to mock it up on the bike to check clearances with the seat etc

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 20, 2019, 09:19:08 PM
In my view, there are a handful of important parts that really 'make' the CR replica true to the original bike:

- Fuel tank
- Exhaust system
- Fairing shape, style, fitment and screen

- And finally the rear hub:
The CR750 was produced as a works machine for Honda to demonstrate the advanced performance that the new model was about to bring to the market. The main campaign for doing so was at the Daytona in 1970, where Dick Mann ended up finishing first, other team members (and breakdowns) aside it was an impressive feat. A very iconic part of the Daytona winning bike, and the subsequent CR kit bikes was the twin leading shoe rear brake

This rear hub was cast in magnesium, but that did not make it light!

A company in Italy used to make a replica of the CR rear hubs, which looked very smart in the images I have seen online but were very expensive and are lo longer available. A CR 'guru' in the UK also made a batch around 10 years ago.
I was going to make a replica of the rear hub by scaling photographs and begging for measurements however this has never really excited me as it was replicating a replica and would only ever be a tribute rather than a detailed replica part.

Cut a long story short, after some serious looking I found an original part:

(https://live.staticflickr.com/65535/48925938466_d8d55e67ec_c.jpg)

(https://live.staticflickr.com/65535/48925940426_15639f4ca6_c.jpg)

Another bit of this jigsaw started.

Also purchased the ignition for the bike so I can start to think about coil and CDI unit lugs:

(https://live.staticflickr.com/65535/48925934941_436fd2468c_c.jpg)

Although this was expensive, it is nicely made and is rated pretty well.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 21, 2019, 10:49:16 PM
A little bit of progress today!

It took me a long time to re-set into CR mode after working on other projects for the last couple of years.

Got a few things done:

Started to re 'hang' the oil-tank:

Fiddly one to get right this and waiting for the correct style bottom brackets:

(https://live.staticflickr.com/65535/48937646663_6308c44a80_c.jpg)

Fitted the right hand gear-change bushing, so that a right hand gear change assembly could be fitted if required:

Fitted up:

(https://live.staticflickr.com/65535/48937638973_591f22ec2f_c.jpg)

(https://live.staticflickr.com/65535/48938375317_56c107c24f_c.jpg)

Welded in:

(https://live.staticflickr.com/65535/48938379782_ce782ddcc5_c.jpg)

This bush accommodates the plain swivel bearing #5

(https://live.staticflickr.com/65535/48938296881_13fc21ffcb_o.jpg)


Front hub

The original CR bikes had a magnesium front hub. This was a simple part with no ribbing

Ribs removed on the lathe

Going

(https://live.staticflickr.com/65535/48938387492_316516b423_c.jpg)

Going

(https://live.staticflickr.com/65535/48938200411_b5b856c516_c.jpg)

Gone!

(https://live.staticflickr.com/65535/48938377782_e670f7a1ae_c.jpg)

As the offset is not quite central I will make up a 2mm spacer to sit behind the right side disc at some point.

Next frame jobs on the list:

- Front seat mountings
- Rear seat hoop and frame cross brace
- Steering damper mount
- Mirror image oil cooler mounts

Other jobs:

- Oil tank filler neck
- Skim the discs (or have them ground) down in thickness. As far as I am aware they were either 4.8 or 6mm thick
- Oil catch tank

Cheers!
CR21
Title: Re: CR750 replica build
Post by: Trigger on October 21, 2019, 10:52:44 PM
Why did you take the cooling fins off the hub ? They are there is cool the hub  :o
Title: Re: CR750 replica build
Post by: CR21 on October 21, 2019, 10:58:51 PM
Why did you take the cooling fins off the hub ? They are there is cool the hub  :o

Hi Trigger,

The CR's did not have this detail on the hub - this is why the ridges were removed.

Thanks,
CR21
Title: Re: CR750 replica build
Post by: Trigger on October 21, 2019, 11:13:11 PM
I think the CR would of had a different hub and a different heat displacement system ?
When I have been fitting new liners to the rear hub, I have had quite a few customers ask, if I could also remove the fins as it is in the lathe and I always refuse because I have known a few people do this and had over heating problems. More so with a front drum but, a few with a disc.
Title: Re: CR750 replica build
Post by: CR21 on October 22, 2019, 07:36:04 AM
I think the CR would of had a different hub and a different heat displacement system ?
When I have been fitting new liners to the rear hub, I have had quite a few customers ask, if I could also remove the fins as it is in the lathe and I always refuse because I have known a few people do this and had over heating problems. More so with a front drum but, a few with a disc.

Hi Trigger,

Yes you are correct it was a different part, and was cast in Magnesium but my bike is a replica. I don't think It will be problematic due to the size of the disk, and surface area change, but I will certainly keep an eye on it,

Cheers,
CR21
Title: Re: CR750 replica build
Post by: Trigger on October 22, 2019, 08:00:15 AM
You will need to get info on heat displacement in alloy of that grade, it is totally different than magnesium. You will always see more fins on a rear drum as, it needs to cool the shoes and bearings. The front hub fins will just cool be bearings, no fins means a overheating problem to the bearings.

Heat always transfers to the smaller area with alloy. Think about removing all the engine fins on a air cooled engine, it will overheat  ;)
I studied this years ago but, can remember all the tech on it and I had a look around last night for the study and data paperwork but, it must of been binned when I moved.
Title: Re: CR750 replica build
Post by: CR21 on October 22, 2019, 08:16:26 AM
You will need to get info on heat displacement in alloy of that grade, it is totally different than magnesium. You will always see more fins on a rear drum as, it needs to cool the shoes and bearings. The front hub fins will just cool be bearings, no fins means a overheating problem to the bearings.

Heat always transfers to the smaller area with alloy. Think about removing all the engine fins on a air cooled engine, it will overheat  ;)
I studied this years ago but, can remember all the tech on it and I had a look around last night for the study and data paperwork but, it must of been binned when I moved.

Hi Trigger,

I understand this, as I also studied it and will do some calcs at some point as I have the part drawn up. Before doing the calcs my gut is that as this bike will never be 'raced' and that I have not removed much material/area I will still have a good factor of safety,

Cheers,
RD17
Title: Re: CR750 replica build
Post by: CR21 on October 22, 2019, 10:58:57 PM
A little more progress from today:

Rear hub stripped and inspected:

(https://live.staticflickr.com/65535/48944086116_98de104a76_c.jpg)

(https://live.staticflickr.com/65535/48944277182_23fc9777a9_c.jpg)


Filler neck bezel offered up:

(https://live.staticflickr.com/65535/48943580298_c2b35797bf_c.jpg)

And welded on:

(https://live.staticflickr.com/65535/48943540688_d998879700_c.jpg)

This replaced the Monza part.

(https://live.staticflickr.com/65535/48943549883_a6387fedcd_c.jpg)

I have linished this down so the weld is flush, but I forgot to get an image!


Seat

Rear hoop tweaked to fit, holes drilled in the fibreglass (always hate that bit!)

(https://live.staticflickr.com/65535/48944283792_aeb7942eaa_c.jpg)

Front seat mounts jigged up:

(https://live.staticflickr.com/65535/48944092426_a8765326b3_c.jpg)

Seat fitting well now, and the bike is starting to resemble a CR!

(https://live.staticflickr.com/65535/48944287307_938a167106_c.jpg)

Cheers
CR21
Title: Re: CR750 replica build
Post by: Napoleonb on October 24, 2019, 05:29:11 PM
Nice find on that hub!
Title: Re: CR750 replica build
Post by: CR21 on October 24, 2019, 09:01:31 PM
Cheers Nap!
Title: Re: CR750 replica build
Post by: philward on October 24, 2019, 10:02:23 PM
Great detail Scott - but you know that already! Having gone through a compromise replica build, really appreciate your build
Title: Re: CR750 replica build
Post by: CR21 on October 24, 2019, 11:31:31 PM
Thanks Phil. Your build is far from a compromise. It is a cracker of a bike.

A few more frame jobs completed today!

A couple of options for mounting the oil cooler on the CR750, a bracket was available for the kit bikes which provided the offset holes for the cooler. I have not seen the frame area on a factory bike, however my suspicion is that they may have mirrored the horn bracket to accommodate the cooler...

(https://live.staticflickr.com/65535/48954201021_d7dd3dccfb_c.jpg)

Folded up a mirror image bracket:

(https://live.staticflickr.com/65535/48953653923_db916a13de_c.jpg)

Welded on some flanged nuts:

(https://live.staticflickr.com/65535/48954210371_1c79f8c411_c.jpg)

Trimmed back and jigged up:

(https://live.staticflickr.com/65535/48954207981_43fc378319_c.jpg)

Welded on and ready for final fettling:

(https://live.staticflickr.com/65535/48953663608_f897662fae_c.jpg)

Still a fair few things on the frame to-do list!

- Rear hoop and cross brace to accept catch tank
- Steering damper mount
- Lower oil-tank mounts
- Lower fairing mounting plates
- Brake stops, and welding of the cable bushes
- Remove chain guard mountings from the swinging arm
- Many other small details!

Cheers,
CR21
Title: Re: CR750 replica build
Post by: philward on October 25, 2019, 10:17:35 PM
Thats exactly what I did Scott
Title: Re: CR750 replica build
Post by: CR21 on October 25, 2019, 10:40:53 PM
Thats exactly what I did Scott

Hi Phil,

Hope it turned out ok? I think a few people have done it, how accurate it is to an original I don't know but I think it will be in-keeping once it is all painted up.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: CR21 on October 25, 2019, 11:43:39 PM
A little progress from today:

Oiltank

Oiltank brackets tacked on, ready to check chain-clearance etc:

(https://live.staticflickr.com/65535/48959958177_1a29a0c686_c.jpg)

Exhausts

The CR75O exhausts are a 'big' part of the appearance of the machine, and something that I would like to get looking tidy.

I believe on the original bikes each exhaust pipe was made of two pressings, which were then welded or seam rolled together. This left the appearance of a seam running at the top and bottom of the pipe. The headers were formed separately and were welded or clamped to the pipes.

Although the shape profile could be achieved with rolling or even sand bending rolled cones, the appearance of a seam is hard to achieve

(https://live.staticflickr.com/65535/48959780551_cbc2368ccb_z.jpg)

The obvious next step was to give it a go...


So a good chunk of time was spent today trying out hydroforming! Something that I have watched many videos on and read about but never tried.

Quick trip out to pick up various fittings to allow the cheapo pressure washer to be hooked up to the sheetmetal assembly, tapped hole in the blanking plug for bleeding air out of the system:

(https://live.staticflickr.com/65535/48959940397_e59428c9e7_c.jpg)

The hardest part of the CR exhaust shape is the curve, so the first flat pattern was knocked up to test the curve profile section. Complete guesswork for the angle and diameter (scaled off of photographs) at this stage and purely for experimentation:

(https://live.staticflickr.com/65535/48959268793_703664dd77_c.jpg)


Seamed together and valve welded in:

(https://live.staticflickr.com/65535/48959202553_76940f7b89_c.jpg)

(https://live.staticflickr.com/65535/48959270758_62447187eb_c.jpg)

Hooked up, with a little safety cage!

Pumped up around 400psi

(https://live.staticflickr.com/65535/48959760646_4a07f8a276_c.jpg)

Happy for a first attempt, but very wavy edges and some buckling  :-\

The pattern next to the product:

(https://live.staticflickr.com/65535/48959762456_59c96c6dc8_c.jpg)


Round two!

Stainless sheet, smoothed pattern shape, special attention on matching the two halves and having smoother curves:

(https://live.staticflickr.com/65535/48959763931_e9964706dc_c.jpg)

(https://live.staticflickr.com/65535/48959954382_1bab1c0401_c.jpg)

(https://live.staticflickr.com/65535/48959767706_52a1c635ba_c.jpg)

The latest attempt above the first attempt and pattern:

(https://live.staticflickr.com/65535/48959218238_cf0f237b44_c.jpg)

What I have learnt about hydroforming today is that the pattern, weld penetration and consistency are key to repeatability.


And that it is with a bit more experimentation I could possibly achieve what I am after...


I think I am going to purchase off the shelf header pipes, however I may experiment with another process I have been wanting to play with for a while which is sand-bending...

Cheers,
CR21
Title: Re: CR750 replica build
Post by: Laverda Dave on October 26, 2019, 12:37:38 PM
Wow, fascinating work. I like to have a go at most things buts hats off to you for trying hydroforming with that pressure and being successful.
Great thread, looking forward to the next installment and photos.
Title: Re: CR750 replica build
Post by: philward on October 26, 2019, 02:45:24 PM
I think I've mentioned it to you before Scott, but when trying to calculate the visual up sweep on the pipes, don't forget that in the picture of Dick Mann on the bike, his weight is on the bike and hence the swing arm is pushed up. I positioned mine relative to the rear wheel spindle as a reference the the picture- but the bike was on the 'A' frame stand when I welded the exhausts together - with no weight on it (which looked the right up sweep). But when everything was assembled and I sat on the bike, the exhausts are lower than I wanted. Just a thought!
Title: Re: CR750 replica build
Post by: AshimotoK0 on October 28, 2019, 10:58:49 AM
Looking fantastic... talked to a guy yesterday at Newark who I get parts from and he told me he just recently sold a CR rear hub for £350 to somebody. Thought it might have been you Scott but seems not.
His was from the estate of Alf Briggs who was Honda UK's Service Manager from the very early 1960's and held all of the race parts at one time. Alf was a close friend of Mr. Honda and when they pulled out of racing  Alf was allowed to keep all of the spares I believe.
Title: Re: CR750 replica build
Post by: CR21 on November 15, 2019, 02:54:00 PM
Hi Laverda, it was pretty simple to be honest but I can't call the result a success yet! I think once I have developed the pattern, along with some very consistent welding it will be more successful. Learnt a lot from the trial parts.

Phil - I remember you mentioning this - thanks for reminding me! So many details on these bikes. 

Hi Ash, I think I know who you are talking about. pm sent for further discussion.

Rear Hub

A little more progress on the replica rear TLS hub.

The CAD assembly is coming along, still a lot of detail to add!

(https://live.staticflickr.com/65535/49068830158_03b5afed91_c.jpg)

(https://live.staticflickr.com/65535/49068830203_758cb939d7_z.jpg)

Cheers,
RD17
Title: Re: CR750 replica build
Post by: CR21 on March 10, 2020, 03:59:22 PM
Hi all,

Small and slow steps on this projects due to other projects consuming heaps of my time!

Anyway a tiny update! The fork bottoms are back from the foundry. How just to figure out the machining techniques and cartridge details  ;)

An original image for reference:

(https://live.staticflickr.com/65535/49644234196_41f68a464f_z.jpg)

And the cast blanks!

(https://live.staticflickr.com/65535/49644526607_6fd1fa1702_c.jpg)

(https://live.staticflickr.com/65535/49644244871_39a85e4e3d_c.jpg)

(https://live.staticflickr.com/65535/49643718633_14a0eb828d_c.jpg)


H2 Eric did a wonderful job of his forks, I have asked him for a little more info.

Cheers,
CR21
Title: Re: CR750 replica build
Post by: Napoleonb on March 11, 2020, 10:08:18 PM
Looking good!
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