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Discussion Starter #1
so, for a honda 350gp race bike project we are going to use a 4ls gt550 brake. but weve been kicking around the idea of using the entire front end. then trading the bike carcass to something more modern. were guessing the 550 has 35mm tubes. anyone have any good reason why we shouldnt do this? obviously it might look like shitola, but were hoping not. this would be the easiest swap to get the brake. no spacers, not measuring, just bolt up and go. any thoughts??

jc
 

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i am basically doing the same thing.... only using a gt 750 front end. sounds like fun



latered
 

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Discussion Starter #3
thanks matt. any idea why ou dont see these things??? is it geometry???


jc
 

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That front end was a one year deal on the 550s. That's why you don't see them. I have one. I'll take measurements off it if you want me to. I don't know about the drum brake front ends but my 75 550 front end is the same pieces as a 750 less one brake.

The reason you don't see them as racebikes is that the motors are pretty tame for a 2-strokes and so much wider than like an RD or a T500. I think the points cover would be one of the first things to drag on my 550. Know it's the first thing to hit the floor when I knock it off the stand.
 

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Joe,

Are you thinking you're going to take the entire front end, including the triple trees and bolt it into the CB350 frame? That's where you may end up with some work. Im not sure the steering stem of the Suzuki will work with the frame of the Honda. Different bearing sizes. If you use the Honda triple trees then you will still need to make up spacers to fit. But if Monkey says it will work then sounds like it will work.

Craig
 

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Discussion Starter #6
i was hoping to swap the stems out, or just drop the spacers under the bottom bearing. like with the cb550/750 clamp swap. yeah, i was trying to avoid running the cb clamps with the zook tubes because of the spacer issue n the axle. im running the 750ss forks with550 trees and the gt750 drum. this is for another project were working on though. as time is getting short, we were thinking it might be a smart thing to do. i just dont recall seeing one setup like that. so i was curious. that and as i went and inventoried the parts pile, i pointed out and noticed that the 750 front end he has is like 9" over. probably not going to work so well!

thanks, ill post up what we find out. i was really more worried about if that front end is good for racing. or if there is some major flaw to it.

jc
 

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that's the setup I've got mounted to my semi-retired BMW. We had to make spacers to take the steering head bearings and get a set of 1" longer fork tubes to make it the same heighth as the one it replaced. Forking by Frank made the tubes. So far, so good
 

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The GT550 and 750 forks are 35mm. The GT380 forks are 33mm. The 72 4LS GT550 front end should be 1 or 2 inches shorter than the stock 72 750 front. I don't recall the exact lengths (28in vs 30in??) but I can check when I get home if you like. The spacing between the fork tubes is narrower for the 550 versus the 750 as the 550 side plates have smaller spacers than the 750 at the axle. The 550 4LS can be easier to fit to other front ends since it's a little narrower.

The bearings on a GT550 front are (IDxODxheight):

25x48x16 upper 27x48x14 lower

The CB350 is:

26x48.5x15.2 upper 30x50x14.4 lower

So it looks like switching the stems is probably the best way to go for you. There's a good damper rod modification for the GT series forks that will improve the Suzuki forks a lot:

http://www.ozebook.com/compendium/suzi/mags/forks.htm

Jim
 

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you will however need to gring the bump on the lower tree to clear the cb steering stop.

do it

latered
 

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Discussion Starter #13
eh....were hacking the stop off anyway.

jc
 
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