Front End Swap GSX-R to GT550

Normandy10 · Post by **Normandy10** » Mon Sep 07, 2020 2:20 pm

Does anybody here happen to know how the dimensions and profile of the steering stem, bearings and triple clamps compare between the 1975 GT550 and the 1992 GSX-R? Interested in doing an inverted fork swap on the GT550 and wondering how much trouble I would be looking for.

jabcb · Post by **jabcb** » Mon Sep 07, 2020 5:36 pm

The AllBalls Racing website lists the bearings needed for conversions.
They only looked at bearing sizes. Any particular swap might not be viable becase of stem length or some other issue.
https://www.allballsracing.com/forkconversion

Normandy10 · Post by **Normandy10** » Mon Sep 07, 2020 7:21 pm

Found them just a little bit ago, but thanks. Looks like it should work with a bearing swap, stem length appears about the same.

dollydog · Post by **dollydog** » Tue Sep 08, 2020 1:54 pm

i put some gt380 forks on a gsx-r400 a couple of years ago, just to see if it would work and they went straight on. does the 97 gsx-r have usd forks on it? if so you'll have a problem and no turning circle because the forks will be right next to the fuel tank

cheers, dd.

jabcb · Post by **jabcb** » Tue Sep 08, 2020 5:32 pm

+1 on needing to investigate this issue.
Take a look at the GT550 & GSXR triple trees on eBay. Might also end up with a change in trail that alters handling.

Normandy10 · Post by **Normandy10** » Tue Sep 08, 2020 7:45 pm

Dolly dog, thanks for the insight from your experience, definitely something to keep in mind, but it would not hurt my head too much to change the fuel tank to something a bit more streamlined if needing some clearance.

Jabcb, the geometry is already altered, previous owner swapped the swing-arm and front from a later Katana, it modded it to dual rear shocks, so the wheel base is currently a good 4 inches longer, but lowered. I am shortening it back to stock length and installing an Ohlins adjustable height shock set-up from a 2011 Duc Hypermotard, part of the motivation to change the front to the GSXR inverted forks. Geometry of the new front is about the same as what is on it now, and they are center-axle, so should not be too different, and should be able to possibly compensate with the adjustable rear ride height. Adding a couple pics of the rear hung in place for mock-up.

Normandy10 · Post by **Normandy10** » Tue Sep 08, 2020 7:48 pm

Top view

dollydog · Post by **dollydog** » Wed Sep 09, 2020 6:08 am

i put upside down forks on my big bang gt250 or the gt285 [can't remember which], and using an old gt250 tank i heated each side up and panel beat a scallop in each side, at the front - a bit like the old cafe racer tanks that had them, they stopped you trapping your thumbs when you had clip-ons fitted. easy enough to do as long as the tank is fuel free

cheers, dd.

Normandy10 · Post by **Normandy10** » Wed Sep 09, 2020 8:14 am

Looks like I can move the front mount studs and rear clamp strap back about an inch, might get enough clearance from that.

Normandy10 · Post by **Normandy10** » Thu Sep 17, 2020 8:47 am

1992 GSX-R inverted front end

Normandy10 · Post by **Normandy10** » Thu Sep 17, 2020 8:49 am

Move the gas tank back about an inch and add 1/4 inch to each side of the steering stops and the turn radius will be just about stock.

Front End Swap GSX-R to GT550

Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550

Re: Front End Swap GSX-R to GT550