Comstars + gsx-r front end

Quick Update of the project: fork has been fitted sucessfully!
Thanks to Rob from the forum who helped me a lot on the process.
Detailled information:
- conversion stem & bearing from Cognito (240$ with shipping & taxes to France)
- GSXR 600 K5 fork with stock caliper, upper & lower triple clamps & axle (630$)
- Comstar wheel from first generation
- new wheel bearing (40$)
- discs from a Susuki hayabusa, OD 300mm (100$)
- conversion flanges to adapt for disc pattern & position (80$)
- spacer for wheel bearing positionning (20$)
- adjustable fork stopper (retroengineered from pictures of Cognito Moto item) (10$)
=> total cost: 1120$ roughly

To be noted that the wheel bore has a lip, quite thick, reducing the diameter. It has to be grinded to fit the new axle & spacer.

So far, it hasn't been tested and one disc is offcentered of 1mm.... Seems I messed up with my measurement, but can be corrected with a 1mm thick washer under the disc.

Bike is looking good, definetely improving the overall stance and line of the bike! :) We will see later about the riding, now working on the wiring!
 

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Quite an expensive conversion but well worth the cost as original forks are very flexy. Now you'll find out where frame needs bracing to compensate for stiffer front end. I think a copy of Tony Foal's Chassis book is in your future?
 
Thatʻs a lot of doh on fork conversion but it looks great, should stiffen up the handling and improve your stopping power. I like the seat mounted lower, maybe a fill in panel on the end of the tank to link the two?
 
crazypj said:
Quite an expensive conversion but well worth the cost as original forks are very flexy. Now you'll find out where frame needs bracing to compensate for stiffer front end. I think a copy of Tony Foal's Chassis book is in your future?

Correct me if I am wrong but isn't this 750 frame made with lighter tubing than the 900F frame, if so then bracing may be even more important?
 
Popeye SXM said:
Thatʻs a lot of doh on fork conversion but it looks great, should stiffen up the handling and improve your stopping power. I like the seat mounted lower, maybe a fill in panel on the end of the tank to link the two?

I can't wait to ride it and test that! The stance is already better and I the position with clip on feels to me already more naturall! Will see that on the road...
Seat will be change to something tailor made for two people and a removable cowl ! Tank painted with its small lower ear cut, all this should improve the look :)
 
CrabsAndCylinders said:
Correct me if I am wrong but isn't this 750 frame made with lighter tubing than the 900F frame, if so then bracing may be even more important?
I never read anyting about frame bracing after a fork swap... It make sense obviously as the fork & wheel axle is stiffer, but for the use I will have (which is purely leasure) is it nonetheless compulsory? I would expect such modification for a track oriented project I would say, but I am no expert :)
 
Personally I always thought the 750F was a better motor than the 'long stroke 900. Honda UK bored 750 to 998 to go endurance racing rather than modify a 900 motor. I know the 750 had way less cam chain problems than 900 (pretty sure I only ever did one 750 compared to unknown quantity of 900 cam chain refits)
 
Quick update on the topic!

I put couple of thousand miles on the clock, and the bike is running like a blast!
- Braking is good, precise and efficient
- cornering is also good, nothing to declare there except at really low speed where it gets a bit hard with the clip-on.
- handling is good
Overall no surprise, and technical improvement from 1979' and 2005 is real, no doubt about it!!

I had to retighten the top nuts of the stem after a while, as a small movement was appearing when breaking abruptly. Since retightening, nothing to declare!
For now I just have to place the steering stopper on the bottom triple T, and I will be completely over with the front end!
 

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Sorry to resurrect an older thread, but Google directed me this way. I have single disk, newer reverse comstars on my 79 cb750 limited. Did anyone find a way to make these work? Are they not as wide as the twin disc versions the OP had issues with being too wide/caliper clearance issues? Any help would be greatly appreciated as I'm gonna go this route myself. Comstars just have the look I'm looking for. Thanks!
 
Sorry to resurrect an older thread, but Google directed me this way. I have single disk, newer reverse comstars on my 79 cb750 limited. Did anyone find a way to make these work? Are they not as wide as the twin disc versions the OP had issues with being too wide/caliper clearance issues? Any help would be greatly appreciated as I'm gonna go this route myself. Comstars just have the look I'm looking for. Thanks!

Post pictures of both sides of your wheel hub. It really depends on that. If the wheel hub is the same as dual disc, there is no reason it wont work. If the hub really is different, then it's easier to get a new wheel to start with than try and make the original work.

I was able to get reverse comstars to work with GSXR fork. No need to ditch them and go for standard comstars.

20200626_210349.jpg
 
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