Author Topic: CR750 replica build  (Read 33014 times)

Offline CR21

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CR750 replica build
« 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!











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.



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



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:






Now stripped to leave the rolling chassis:







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!) 



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



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
« Last Edit: September 13, 2017, 12:02:46 PM by CR21 »

Offline MarkCR750

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Re: CR750 replica build
« Reply #1 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.

Suzuki GT250A (Nostalgia)
1977 K7 CR750 (lookalike, what of I’m not sure)
Ducati 900SS (Soul & Speed)
Ducati M900 Monster (Handling & character)
Thruxton 1200 (suits me)
James Captain 197 (pure adrenaline, i.e. no brakes!)
"Eff yir gitten awvestear yir gooin te farst"
Sir J.Stewart.

Offline CR21

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Re: CR750 replica build
« Reply #2 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

Offline MarkCR750

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Re: CR750 replica build
« Reply #3 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
Suzuki GT250A (Nostalgia)
1977 K7 CR750 (lookalike, what of I’m not sure)
Ducati 900SS (Soul & Speed)
Ducati M900 Monster (Handling & character)
Thruxton 1200 (suits me)
James Captain 197 (pure adrenaline, i.e. no brakes!)
"Eff yir gitten awvestear yir gooin te farst"
Sir J.Stewart.

Offline westfieldandy

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Re: CR750 replica build
« Reply #4 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

Offline CR21

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Re: CR750 replica build
« Reply #5 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

Offline Laverda Dave

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Re: CR750 replica build
« Reply #6 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
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota

Offline Johnwebley

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Re: CR750 replica build
« Reply #7 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
lifelong motorcycle rider,and fan

Offline CR21

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Re: CR750 replica build
« Reply #8 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!




















Cheers
CR21
« Last Edit: September 13, 2017, 12:04:01 PM by CR21 »

Offline MarkCR750

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Re: CR750 replica build
« Reply #9 on: August 27, 2016, 07:25:11 AM »
Very nice, are they from mr Boyce?
Suzuki GT250A (Nostalgia)
1977 K7 CR750 (lookalike, what of I’m not sure)
Ducati 900SS (Soul & Speed)
Ducati M900 Monster (Handling & character)
Thruxton 1200 (suits me)
James Captain 197 (pure adrenaline, i.e. no brakes!)
"Eff yir gitten awvestear yir gooin te farst"
Sir J.Stewart.

Offline CR21

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Re: CR750 replica build
« Reply #10 on: August 27, 2016, 09:45:23 AM »
Very nice, are they from mr Boyce?

They certainly are  ;)

Offline CR21

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Re: CR750 replica build
« Reply #11 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!





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:



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
« Last Edit: September 13, 2017, 12:04:27 PM by CR21 »

Offline MarkCR750

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Re: CR750 replica build
« Reply #12 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
Suzuki GT250A (Nostalgia)
1977 K7 CR750 (lookalike, what of I’m not sure)
Ducati 900SS (Soul & Speed)
Ducati M900 Monster (Handling & character)
Thruxton 1200 (suits me)
James Captain 197 (pure adrenaline, i.e. no brakes!)
"Eff yir gitten awvestear yir gooin te farst"
Sir J.Stewart.

Offline CR21

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Re: CR750 replica build
« Reply #13 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

Offline UK Pete

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Re: CR750 replica build
« Reply #14 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

 

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