|Project: Vintage Superbike
|December 18, 2006 -- I have a new winter project: I've decided to prepare a bike to compete in the AHRMA Vintage Superbike
Heavyweight class. I'll still be racing my 749R, but I've been a big fan of the AHRMA Vintage Superbike class (www.ahrma.org) since its
inception a few years back, and decided to step up and give it a try. (Follow this link for more of my racing info.)
Bikes of this era are my "vintage" bikes. While I enjoy and respect the older bikes, I just don't have any emotional connection to them.
The original AMA Superbikes were my first real exposure to roadracing, and I still remember how cool it was to read about (not much TV
coverage back then) Eddie, Wayne, Wes and company wrestling those monsters around the racetrack.
First on the agenda was choosing the bike. Rules dictate pre-1983 bikes, and allow the replacement of the forks, wheels, brakes,
swingarm, etc. Tank, seat, fenders, bodywork must be stock and remain on the bike. Engine mods are pretty much wide open, with
displacement limits based on engine architecture.
Naturally, my first inclination was to investigate Ducatis. Bevel-drive and early belt-drive Ducatis fit into the class rules, but making one
competitive -- at least in the Heavyweight class -- was going to be costly and difficult. The 750SS and the 900SS are hard to find,
expensive, and even with a fully built motor would be 30 to 40 hp down on the inline fours. Duplicating the Schilling/Neilson "California
Hot Rod" would not only be expensive, but the rules allowing modern suspension components and the improvement in race tires over
the past two decades have negated much of the advantage the smaller, lighter twin would have enjoyed back then.
So I looked towards the land of the Rising Sun. My first streetbike was a Kawasaki 1000, and second streetbike (and first sportbike) was a
1982 Kawasaki GPz550. Not to mention I've always lusted after an Eddie Lawson Replica KZ1000. So, I started investigating Kawasakis.
My first thought was a 1982 GPz1100, but the rules require the bike to displace no more than 1025 (which would require cylinder
resleezing and new pistons) and can run smoothbore carbs no larger than 29mm (stock fuel injection must be removed). Those
restrictions, coupled with the weight and size of the bike (it has a 60-inch wheelbase!) convinced me to keep looking.
I started to look closer at the 1982 GPz750. Smaller and lighter than the GPz1100, the rules allowed it to be taken to 931cc and could run
without the intake restrictions of the big bikes. One of the fastest bikes in the class has been a 1977 GS750 punched out to 918cc and
making 115 hp. While some of the litre bikes are putting out over 130hp, the smaller GS750 was still faster around the racetrack.
The deal was sealed when Jeff Hinds, owner of Hinds Motorsports, one of my sponsors and a Vintage Superbike racer (and Kawasaki
nut) sourced a 1982 GPz750 for cheap. I loaded it up and brought it home.
Okay, so it's not the most handsome bike in the world. But considering pretty much everything other than the engine, frame and
bodywork gets replaced, it was a good racebike platform.
Right now, I'm still researching suspension components and chassis improvements. Forks have to be from the same brand of
motorcycle, conventional design (no upside down forks), and no larger than 41mm, so we're looking at 95-97 ZX6R forks and front wheel.
Out back, a ZRX1100 swingarm, which is basically a replica of the swingarm on the KZ1000S1 (the bike Lawson actually raced), will be
fitted (rules require the swingarms to be period aftermarket or of a like design, and most retain twin shocks). A ZX6E wheel will be used
(max rim width is set at 4.5").
Part of the challenge in building these bikes is not only grafting on modern suspension components and dialing in more modern chassis
geometry (less rake and trail), but keeping the ride height up to maintain ground clearance (the Muzzy Kawi superbikes of the era sat
1.25" higher than the stock bikes), which isn't easy when you're replacing 18" and 19" wheels with 17-inchers. But that's all part of the
I probably won't do too much to the motor at first -- just freshen it up -- so I can concentrate on the chassis. Once I'm comfortable with the
bike, I'll get together with J.D. Hord at Hordpower (who builds my Ducati engines, but is extremely knowledgeable and experienced in all
aspects of building fast racebike motors of any type) and see what we can pull out of the old girl. We can go to 880cc with custom
pistons and relining the cylinder, then it's the usual big valves, big cams, good porting, etc. We have a few tricks up our sleeves, and
don't think 120hp at the rear wheel is out of reach (the stock bike makes 65hp).
That's it for now -- I'll post more as I get the bike stripped down and start modifying the frame and grafting on new suspension bits and
December 26, 2006 -- Picked up some parts last week from Cycle Search International (www.800390bike.com), a local bike salvage
operation. Went to look at a Kawasaki ZRX1100 swingarm they had, and ended up coming home with the swingarm, a rear ZX6 wheel,
cush drive and rotor, a front ZX6R wheel, and a set of ZR7S front calipers. Owner Mike Gifford was extremely helpful, and his prices were
lower than the parts I'd been watching on eBay. Plus, it's always helpful when you're doing a custom project like this to be able to
actually see the parts and judge what will work with what.
I've decided to keep a spreadsheet of expenses for this project. Usually I like to stick my head in the sand when it comes to the cost of
building racebikes, as the total usually greatly exceeds every initial estimate and putting it down on paper simply makes what we spend
on this "hobby" all to real. However, I think the cost on this project will be surprisingly low, so I'll be keeping track of expenses as I go
along. Check here for the initial tally.
(Click on thumbnails to enlarge)
|Project Parts Needed
I'm looking for, among
other things, a race 4-1
system and 95-97
Kawasaki ZX6R front end.
Click on the link for more
|Project Parts For Sale
Pretty much everything but the
frame, engine, and bodywork
goes. Click on the link for more