Vintage Superbike Project
I bought this bike back in late 2006 with the intention of turning it into a racebike for AHRMA's Vintage Superbike class. I've raced
modern bikes, mostly Ducatis, for years, but was interested in building a bike for the class. Work, racing, life, etc., all interfered, and I
haven't messed with it now for a couple of years. With AHRMA recently announcing a new "Next Generation" Vintage Superbike class
for 83-92 bikes, I've decided I'd rather focus my efforts on the Ducati 888 I'm building for the new class. Therefore, this bike is now up for
The bike is a 1982 Kawasaki GPz550, the only year they made a twin-shock GPz750. It was a "shed bike" when I bought it and hadn't
been ridden for several years. Most of the parts were there, and the engine turned over, so I bought it and brought it home to the shop.
Why a 750 in a class of 1000cc bikes? The GPz 1100 would require re-sleeving to meet the class displacement maximum of 1025cc, and
the fuel injection would have to be replaced with carbs. Those restrictions, coupled with the weight and size of the bike (it has a 60-inch
wheelbase) convinced me the smaller and lighter 750 was the way to go. The rules would allow it to be taken out to 931cc and I could
run without the carb/intake restrictions of the litre bikes.
Here's what it looked like when I brought it home . . .
Not beautiful, but pretty much intact, which is often rare for a 25-year-old bike.
Up on the workbench it went, where I stripped it down to the bare frame. The only thing that would remain would be the frame,
engine, and bodywork, so everything else went in boxes or was sold.
I had several major goals with the chassis: improve the front and rear suspension; strengthen the frame, swingarm, and forks;
lighten and update the wheels; increase the ground clearance; and improve the geometry.
Towards those goals, I installed a set of ZX6R forks, which were the only 41mm conventional-design fully adjustable cartridge forks
Kawasaki made. (The rules require the forks be from the same mfg., convential design, and no larger than 41mm). To accomplish
this, I had my machinist press the GPz stem into the ZX6 lower triple, then had a custom top triple with bar mounts (again, required
by the rules) made. I added a ZX6R 3.5" x 17" front wheel, ZX6R dual rotors, and ZR7S calipers (rules require two-piston calipers).
Out back, my machinist did a little whittling to get a ZXR1100 braced tubular aluminum swingarm mounted up. These Eddie Lawson
Replica swingarms look fantastic on these bikes, and are not only much stronger, but make mounting the 4.5" x 17" ZX6 rear wheel
(again, the rules require no larger than 4.5" rear wheels) much easier.
Obviously, there's still plenty of work to finish this project. The chassis is close to complete, with caliper mounts still needing to be
made, and the cush surface of the rear wheel needs milled down to align the sprockets properly. Boeywork needs painted and the
seat needs recovered, and rearsets will need to be fabricated. New proper racing shocks will need to be purchased. My plan was to
fit up an exhaust system and a set of smoothbore carbs and leave the engine alone until I was sure I had the chassis well sorted.
After that, there are a ton of go-fast goodies available for these old Kawasaki motors, so building a fast motor should be the easy
Price is $1,750, which is what ratty stockers are going for. Nice ones fetch $4,000 to $5,000. Not a lot of
82 GPz 750s were ever made, so they can be difficult to find in any condition.
I can deliver the bike at no charge to the any AHRMA roadrace east of the Mississippi.