Topic: '75 CB750F SS - GSXR Fork conversion

[Johnny340]

I bought the All Balls bearing conversion for '06 GSXR forks on my '75 CB750F and have a couple questions.
The upper bearing race doesn't fit very tight and can spin.  Also even bottomed out, it doesn't fit down very far so the bearing and dust cover don't fully cover the top. (see pic) It looks like it can go in further in the pic but it is bottomed out on the inner frame head tube.  Is that normal?
Also, is there a better top triple clamp that would allow the forks to slide down more in the lower triple clamp for more 'factory' geometry?  (It's about 2" shorter right now)
Thanks for the input!

[Jwexperience]

I have the same front end on a '78ss and my top race doesn't spin but I also reused the 750 tapered race. Did you have a 750 stem pressed in or a aftermarket stem?
As far as being 2" shorter, I used the gsxr front rim with a cbr600f2 rear wheel, both 17". Then used cb900rear shocks which are about an inch or two longer than stock. My bike handles pretty good, might lower the rear a little to see if it slows the steering a little but it's close.


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[Johnny340]

Thanks for the reply.  Your bike looks awesome!
I've mocked it up with the stock GSXR 750 stem and it fits by using only the Suzuki top nut to do the holding; just like the original Honda setup uses. (the lower nut/locknut threads are too low from the original Suzuki setup to be used).  When you say "750 stem" do you mean the stock Honda stem?  The original Honda bearing was a loose ball bearing type and the All Balls one is a nice tapered roller bearing style.
I'm planning on using a 19" front wheel.

[calj737]

I'm planning on using a 19" front wheel.

You will very likely have conflict between the tire and the exhaust with a 19" tire and the GSXR forks. The offset of the GSXR fork is much smaller than the stock 750, so the top clamp and back edge of the tire are much closer to the tank (top clamp) and the motor). Even mocked up, it may not show, but under front end compression it will conflict.

Sliding the triples down the tubes (or tubes up through the clamps) isn't really possible. The fork tubes have tapers that prevent them from being clamped in an arbitrary location. I'd suggest you consider a custom triple tree with more offset, and perhaps a dropped clamp bridge if you are attempting to rectify the geometry changes. You can ring up CognitoMoto and discuss it with them as an option.

[Jwexperience]

I have the all balls tapered bearings and some people press out the stock stem and use it in the gsxr triple. Mine uses a cognito moto stem pressed into the gsxr triple.


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[Johnny340]

You will very likely have conflict between the tire and the exhaust with a 19" tire and the GSXR forks. The offset of the GSXR fork is much smaller than the stock 750, so the top clamp and back edge of the tire are much closer to the tank (top clamp) and the motor). Even mocked up, it may not show, but under front end compression it will conflict.

Sliding the triples down the tubes (or tubes up through the clamps) isn't really possible. The fork tubes have tapers that prevent them from being clamped in an arbitrary location. I'd suggest you consider a custom triple tree with more offset, and perhaps a dropped clamp bridge if you are attempting to rectify the geometry changes. You can ring up CognitoMoto and discuss it with them as an option.

Thank you for that insight as I haven't even checked pipe or tank clearance yet.  I looks like there are a couple centimeters of thick area on the forks to slide them down more but I'll check with Cognito Moto about their triple clamps.  I was planning to use their front hub already.  I assumed a small front wheel with an already shorter set of forks would make it handle too quickly so I'd like to get a 19" wheel to work.

I have the all balls tapered bearings and some people press out the stock stem and use it in the gsxr triple. Mine uses a cognito moto stem pressed into the gsxr triple.

Did you use an All Balls 'conversion kit' for Suzuki forks? I assumed their conversion kits catered to matching up the different brands and didn't require any steer tube swapping.  (btw, you are missing a front fender bolt.)
It looks like your wheel is close to the pipe even with the small front wheel.  You also went with longer shocks which I thought was make the handling even quicker...  You are happy with the way it turns?  Does it have high speed stability?  I have a steering damper I was going to mount up too.

[Jwexperience]

I'm not a geometry guru but I believe the shorter offset makes up some of the difference in fork length and wheel diameter. It does turn in a little quicker but it's not to the point where it feels like it's falling into a turn if you know what I mean. I was thinking of putting shorter rear shocks on but I'm also debating on getting the adjustable offset triples from cognito. I'm leaning towards the triples and I'm thinking if I can add about 15mm's to the offset then I will add some stability and slow the steering a bit. I will also gain steering stops and better turning radius. I haven't done much time on the highway so I do t have a great idea of high speed stability but it feels solid going 50-60 on some back roads. I like the ride and handling. My biggest gripe is the position of my feet, they could be back another 2" or so.
As it sits, I have plenty of room between the wheel and pipes. I am aware of the bolts, they're an odd size so I have to pick some up next time I go to the hardware store. Thanks


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[sinister902]

you might be able to find what's called a drop triple for the GSXR, which can be flipped to make it a rise triple and add some length to your front end. But as cal said, with the gsxr triple trees' degreased offset you may not have very much turning radius before contacting the tank, and you may also smack into the head pipes under a hard compression of the front end. That's why cognito offers a 45mm offset set of triple trees.

[Johnny340]

I thought I researched this well but does nobody use a larger wheel with the stock triple clamps?  What about those threads on using a Harley front hub?  Some of the things I've read were for the CB550...is that frame able to handle the small offset of the Suzuki triple clamps?  I'm willing to put up with the short steering throw but a tire into the pipes is not an option..

As for the All Balls conversion bearings, it seems that the stock Suzuki stem is too short for the bearing preload nut so I'm back to square one there too.  Alex at All Balls is helping me to try to find a solution there and is excellent to work with btw.  Good company!

Yes, the smaller offset of the triple clamps is compensated for with the smaller wheel resulting in around 4" trail which apparently is ideal no matter how you achieve it.

Any other comments are welcome.

[Johnny340]

Just an update in case anyone searches for USD forks on a CB750.
The GSXR triple clamps will need a different stem such as the one made by Cognito Moto. You will still have limited steering with the small offset triple clamps due to tank clearance. CM also sells steering stops for the lower triple clamp if you don't want to make your own.
As for the wheel size, I'm going with 17" front and rear to help compensate for the increased trail from the smaller offset clamps and also for a good selection of modern sport bike tires.
From my research, rather than messing around with Harley hubs and spacers for the front wheel, it is worth buying the sweet looking hub from CM. it seems expensive at first but is probably cheaper in the end for this a proper looking and safe setup.

I might do a build thread if there is any interest.

[Jwexperience]

Are the steering stops you mentioned from cognito for the stock gsxr triples?


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[calj737]

Are the steering stops you mentioned from cognito for the stock gsxr triples?

Yes. Or make your own.

[Ericcb750]

Hey Guys, just seeing this for the first time. I have a complete front end coming from Cognito shortly. Unfortunately in order to use the steering stops that cognito sells on the stock GSXR Lower triple, you will need to drill and tap a hole for the M6 screw that holds the steering stop to the lower tree, You may have to cut the stock steering stop off.... I'm going with their upper and lower tree and stem so the stops are built in.

Have a build thread going in the project section. The last piece , my hub was being anodized at the beginning of the week so i'll be sure to get some photos/info up in the project thread when everything arrives. I have the GSXR lower triple, tubes, calipers and some sweet brand new stainless Galfer wave rotors waiting for the rest of the goods to arrive....

I'm super excited to see how this puppy stops and handles opposed to the stock CB750 front end.

[Johnny340]

Hey Guys, just seeing this for the first time. I have a complete front end coming from Cognito shortly. Unfortunately in order to use the steering stops that cognito sells on the stock GSXR Lower triple, you will need to drill and tap a hole for the M6 screw that holds the steering stop to the lower tree, You may have to cut the stock steering stop off.... I'm going with their upper and lower tree and stem so the stops are built in.

Have a build thread going in the project section. The last piece , my hub was being anodized at the beginning of the week so i'll be sure to get some photos/info up in the project thread when everything arrives. I have the GSXR lower triple, tubes, calipers and some sweet brand new stainless Galfer wave rotors waiting for the rest of the goods to arrive....

I'm super excited to see how this puppy stops and handles opposed to the stock CB750 front end.

I checked out your build thread and it looks great so far!  Why did you decide on an 18" front wheel and what tires do you plan to use? Also, what offset triple clamps did you order?
Thanks, I'll plan to cut off the stock GSXR stops and tap a hole for the Cognito ones.

[Jwexperience]

I just ordered a set myself, I spoke to them about a month ago and he said they didn't have any stops unless I bought the triples. Thanks for mentioning...$27 is better than $700!


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[gwallis]

I absolutely love the look of the bike.  What brand is the exhaust headers?

[turboed13b]

I thought I researched this well but does nobody use a larger wheel with the stock triple clamps?  What about those threads on using a Harley front hub?  Some of the things I've read were for the CB550...is that frame able to handle the small offset of the Suzuki triple clamps?  I'm willing to put up with the short steering throw but a tire into the pipes is not an option..

As for the All Balls conversion bearings, it seems that the stock Suzuki stem is too short for the bearing preload nut so I'm back to square one there too.  Alex at All Balls is helping me to try to find a solution there and is excellent to work with btw.  Good company!

Yes, the smaller offset of the triple clamps is compensated for with the smaller wheel resulting in around 4" trail which apparently is ideal no matter how you achieve it.

Any other comments are welcome.

I have a 19 on mine.

[Jwexperience]

I absolutely love the look of the bike.  What brand is the exhaust headers?

Delkevic header with a cone engineering muffler. Real nice exhaust and great price point.


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[gwallis]

You see... that s what I thought it was.  I also have the Delkevic Exhaust Header... however, the end of my exhaust sticks out about 15 degrees past being parallel with the frame of the bike.  When adding a muffler it really sticks out there.

It does not look like yours does this.  Have I installed the header incorrectly?  Is there some 'play' in the exhaust collector that allows you to turn the end more into the bike so it does not stick out so far?

'Thanks' for the reply!

[Jwexperience]

As long as it's fitted together properly there shouldn't be much play. Mine is angled out slightly but it doesn't stick out far.


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[Johnny340]

As long as it's fitted together properly there shouldn't be much play. Mine is angled out slightly but it doesn't stick out far.

That looks perfect. 
Hey, what size rear tire have you got on there.  I'm wondering if a 160/60x17 will fit in the stock SS swingarm and also not hit the brake stay.

[Jwexperience]

I don't think it will fit the 75/76 but it will def fit the 77/78 swingarm. I think the stay would need modification to work. I had to weld a bracket onto my swingarm to hold the brake mount and stop it from swinging. I used a 92 cbr600f2 rear wheel and brake setup. Mixed and matched some spacers to line it all up.


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[Johnny340]

I don't think it will fit the 75/76 but it will def fit the 77/78 swingarm. I think the stay would need modification to work. I had to weld a bracket onto my swingarm to hold the brake mount and stop it from swinging. I used a 92 cbr600f2 rear wheel and brake setup. Mixed and matched some spacers to line it all up.

Yes, the current brake stay rod on my '75 is mounted on the top of the swingarm which looks too far over as it is.  I'm sure I'll need to move that mount outward and/or modify the rod.  As for the swingarm itself, is it the same as your 77/78 and can handle 160mm tires?  Thanks!

[Jwexperience]

The 77/78 was the widest swingarm. You might have to go with a 150 at most because your front sprocket will be inboard too much compared to the 77/78.
Even with my 78 engine, I had to use an offset front sprocket to get the sprockets to line up. Might not matter for you though if you are staying with your stock hub and lacing up a wider rim. I laced a wider rim to my '76 k model and was able to get a 150 on it with no mods, only moved the brake stay to the outside of the swingarm mount. The chain and swing arm were close to rubbing with the 150 but I put over 3k miles on it with no issues.


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[Johnny340]

Thanks for the reply.
I didn't realize that the counter sprocket was not as far out on the 75/76 engine.  I'm using a 4.25" rim on the stock disc hub which looks like the same dimensions as a drum hub and it looks like a sprocket spacer will be necessary.
Since this is so far off topic now, I'll start a (another) new thread regarding tire size.
Thanks for the info everyone.  Cognito Moto order placed!