Author Topic: CR750 replica build  (Read 33005 times)

Offline onethumb

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Re: CR750 replica build
« Reply #30 on: January 04, 2017, 02:43:59 PM »
Sweet work. Makes me embarrassed to put my build up now. 


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Offline Johnwebley

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Re: CR750 replica build
« Reply #31 on: January 04, 2017, 02:54:35 PM »
this is brilliant,

   the quality is superb,did you do the folding/bending and welding ??
lifelong motorcycle rider,and fan

Offline CR21

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Re: CR750 replica build
« Reply #32 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

Offline CR21

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Re: CR750 replica build
« Reply #33 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.



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:



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  ???



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:



L shape folded on the folding table:





Welded:



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



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



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





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



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.




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

Cheers
CR21
« Last Edit: September 13, 2017, 12:16:50 PM by CR21 »

Online K2-K6

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Re: CR750 replica build
« Reply #34 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?

Offline CR21

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Re: CR750 replica build
« Reply #35 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


Offline paul G

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Re: CR750 replica build
« Reply #36 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
Honda CB400 4
Honda CB550 K3 (sold)
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer (Sold)
Honda CD175 sloper

Offline CR21

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Re: CR750 replica build
« Reply #37 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:

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Offered up to the frame and tank etc:



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:



Measured out using the shock mounts as a datum:



Now ready for welding tomorrow morning:



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.



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:



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!





De-burred and ready to go!



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

« Last Edit: September 13, 2017, 12:17:22 PM by CR21 »

Offline yozzer74

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Re: CR750 replica build
« Reply #38 on: January 06, 2017, 12:01:32 AM »
Loving this build

Offline paul G

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Re: CR750 replica build
« Reply #39 on: January 06, 2017, 08:11:08 AM »
Loving this build

Me too detail is superb  ;D
Honda CB400 4
Honda CB550 K3 (sold)
Honda CB750 UK K1
Kawasaki Z650 C2
Kawasaki Z650 cafe racer (Sold)
Honda CD175 sloper

Offline CR21

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Re: CR750 replica build
« Reply #40 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:





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!










 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:








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



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



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.





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
« Last Edit: September 13, 2017, 12:18:47 PM by CR21 »

Offline MCTID

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Re: CR750 replica build
« Reply #41 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.


Now: 2008 CB1300S, CB750K4, 1970 Bonneville. Various other 1960's 650 Triumph T120's/ TR6's/ TR6C's (all in bits...many, many bits unfortunately). Previous: 2007 CB600FA, 1976 CB500 Four. BMW F800ST. GS750E. ZZR1100. CB1300 (2). ZXR1200S. VFR800. CB750 Nighthawk. CX500. XS500 Yam. Suzuki GT500. BSA A10. Various Lambrettas. Zundapp Bella (honest).

Offline mike the bike

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Re: CR750 replica build
« Reply #42 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.
Where's that 10mm socket got to?

Offline CR21

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Re: CR750 replica build
« Reply #43 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

Offline MarkCR750

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Re: CR750 replica build
« Reply #44 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! 😄
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.

 

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