Been a bit busy since the last post. As promised, albeit a few days late, I've tackled the front suspension. For the front suspension, something a bit more modern was wanted. A supersport inverted fork layout was selected, for increased performance in steering and braking and for the aesthetic upgrade. From the factory, the GS500 comes with a very underwhelming front end, especially for anyone over about 140 lbs. In its stock form, an upgrade is a huge improvement, so when modifications are being done to up power output, suspension and brakes ought not be overlooked. Thanks to the wonders of craigslist, I was able to pick up a front suspension off a wrecked '06 Suzuki GSX-R600. I was told by the seller that one fork was slightly bent, but everything else was in great shape. The front wheel, however, was a total loss. I paid a great price for this condition. Unfortunately, after further inspection, this description was a bit of an understatement. The guys at G P frame in Napa, Ca did a wonderful job getting the front end all sorted out. Both forks needed lots of work, along with the upper and lower triple trees and the axle. Far from the one fork needing slight adjustment I had expected. After a hole in my wallet, I was left with a great front end to use.
Unfortunately, the front wheel that came on the front end was not salvageable, despite the efforts by G P frame. I ended up picking up a 98 GSXR 600 front wheel off ebay for a great price. About 1/4 of what an 06-07 GSXR wheel would cost. Unfortunately, these are not a direct bolt up. The brake rotors that came with the front end would not bolt up to the older gsxr wheel. Instead, I picked up a set of Hayabusa brake rotors. They bolt up the wheel, but weren't a direct fit to the brake calipers. More on that in a bit.
Now the GS500 is a much smaller, less expensive bike than the supersports, and as such have a much smaller, weaker suspension set up. The GSXR front end does not bolt up to the GS500 frame. To solve this, I went to Bob Broussard, an experienced GS500 builder who has done this front suspension swap many times. The GS500 stem was pressed out of the GS lower triple, welded to add some material, then shaped and pressed into the GSXR lower triple. This allows the lower triple to mate to the GS500 frame, however, the top GSXR triple tree needed an adapter to be made. I had to modify the frame slightly to use the GSXR ignition module, just for clearance. A new steering stop will need to be made and welded to the GS frame, however, I haven't tackled this yet. This new steering stop will also act as a point from the GSXR steering damper to bolt to.
After adapting the front suspension to the frame, attention was turned to the wheel and brake issues. The 06 GSXR axle fit the older wheel great, however the spacer used to center the wheel was too large, causing the wheel to sit off center and rub. About 5mm was removed from the surface that meets the wheel on the spacer, centering it while mounted. The brake rotors sit about 2mm further apart than the older ones, however, play in the brake calipers will easily make up for this. The calipers, however, did need to be spaced out to clear the larger 320mm diameter Hayabusa rotors over the 310mm GSXR rotors. Honda sells a caliper spacer that would have achieved this goal, however, all the local dealers were out of stock and it offered a good excuse to practice my lathe skills and save $25. I picked up some 1" diameter aluminum bar stock, and turned a set of spacers for the calipers.
The new, updated hand controls require some serious rewiring. As I am converting to fuel injection concurrently, significant wiring needs to be down there as well. As such, I removed the stock wiring harness from the bike, and used the opportunity to start cleaning things up. Some serious modifications to the frame were completed as well. As I will be running a solo seat, an abbreviated tail for aesthetic reasons, and a under bike mounted exhaust, I ground off the passenger pegs, exhaust hanger, and a section of the rear frame. Also painted the front wheel while it was without a tire. Now onto the pictures:
Before cutting and with the stock front end.
Stock front suspension
Comparison between the old and new front forks. Note that the GS stem has already been pressed into the GSXR triple tree
With the GS stem, everything bolts up to the frame like stock
The aluminum adapter made to fit the GSXR top triple tree and the steering lock ground down for clearance of the GSXR ignition module
Mock up with the new controls in place, older wheel, etc
Calipers mounted up with the 5mm spacers I made in place
Profile with the new front end
Stripped down, waiting to go under the knife