1983 cb900 USD conversion

SebastianM

New Member
Hey guys,
I am planning a USD-fork conversion for my 83 cb900f sc01.
According to my current information, both FZR 1000 LE3 and yzf 750 forks will fit almost "plug and play".
Any pros and cons to those two forks?

thx in advance..

Sebastian
 
are you using the entire USD front end, wheel and all? or are you looking to use the forks and adapt your stock wheel?
 
SebastianM said:
I want to use "custom" spoke-wheels with a cb 550f hub...
If you don't have access to machine shop equipment, you're going on a costly endeavor.

Rather than the USD, I'd take a look at a set of 94 CBR600F2 forks. Beefy, basically a direct swap. Then, you'll only have to pay someone to make you an axle, caliper spacers, and wheel spacers.
 
you'd be better off with a metric bearing dual disc hub from a Harley Davidson if you're trying to do spoked wheels.....as they would still be 40-spoke and use much closer to correct bearing size for an USD forkset's axle.

The fzr1000 forks and triples don't have all that bad of geometry all things considered and will go into the neck of the cb900 with some bearing conversions from All Balls Racing.....

the fzr1000 uses I think a 20 or 22mm front axle if I'm not mistaken....which could prove to be a chore since the metric bearing variant of Harley wheels uses 25mm axle size. That said, ZX7/ZX9 USD forks use 36mm offset and 25mm axle, with 6-piston tokiko brakes. I've used those a lot. ZX7/9 forks with a harley hub and you'd just need centering spacers and rotor spacers made up to take 5-bolt GSXR or ZX rotors....
 
J-Rod10 said:
If you don't have access to machine shop equipment, you're going on a costly endeavor.

Rather than the USD, I'd take a look at a set of 94 CBR600F2 forks. Beefy, basically a direct swap. Then, you'll only have to pay someone to make you an axle, caliper spacers, and wheel spacers.

The F2 swap has been done a lot, also thr F2 swingarm swap.
 
The FZR 1000 LE3 uses a 17mm axle! I can simply swap the bearings in my cb550 hub to fit the 17mm axle ... correct bearing-size should be something like 42x17x12.

Do you have more information about the bearings for the steering stem? To be honest, I thought I have to press out the stem of my cb900 and press it in the FZR bridge.....
 
I know people have pressed the 900 stem into F2 clamps and it works well. Some people have even bored the 900 clamps out to accept F2 forks but I am not sure if the size of the FZR tubes would allow this.
 
Can't you shorten the FZR stem and use an All-Ball conversion to fit the frame? That's exactly what I did with my RD, though I used older non-USD FZR 600 forks. I used the stock RD hub and made spacers for the hub and brake rotor.
 
SebastianM said:
The FZR 1000 LE3 uses a 17mm axle! I can simply swap the bearings in my cb550 hub to fit the 17mm axle ... correct bearing-size should be something like 42x17x12.

Do you have more information about the bearings for the steering stem? To be honest, I thought I have to press out the stem of my cb900 and press it in the FZR bridge.....

if it's 17mm you're in luck....stock bearing is 42x15x13

https://www.123bearing.com/bearing-DG1742-RS-C3-KOYO.php

for neck bearings:

http://www.allballsracing.com/index.php/forkconversion

if you punch in cb900f and scroll all the way down to FZR1000 you'll see you need a 25x47x15 top bearing and a 30x55x17 bottom bearing, allballs part numbers 99-3518-5 and 99-3519-5 respectively.

if the FZR stem isn't more than a quarter inch between bearing seats, the all balls kits come with big fat washers to put under the bottom bearing or under the top race in the neck (or both) to take up about 1/4".
 
The big thing is trying to get the trail to 95mm so that it handles properly. I'm doing a f3 front end with cb900f triple bored for the f3 forks.
 
The thing I wonder about is the reduced ground clearance, I have F2 forks and wheels to put on mine and I have read of how much lighter the bike is and feels but it does lower the bike.
 
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