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Making a Kawasaki Z1 race ready. Again.

July 01, 2011

Story by Arthur Kowitz

Superbike racing
The author, competing in a WERA endurance in 1975.

Modern vintage
The Z1, revived.

frame and swingarm
The chassis and swingarm, ready to race.

The heart of the beast.
Making the Z1 better than new.

racing pipes
A custom racing exhaust makes all the difference.

race paddock
Getting sorted at the track.

Superbike restored
Headed for AMA Vintage Motorcycle Days.

My first Kawasaki was a brand new 1968 A7 Avenger. It was a rattly, short, stubby two-stroke twin that was exhilaratingly fast compared to the lawnmower powered bicycle and little Hondas of my earlier teens.

A year or so later, as a sophomore at the University of Florida, I took out a $1,000 student loan and bought a shiny white Mach III 500cc triple. As we all know, that was one really fast motorcycle, and I was addicted. And, yes, I paid the loan back as agreed.

This rev-happy beauty seduced me into dropping out of college and buying the local Kawasaki "dealership" for $500.

A few short years later, the Z1 burst onto the scene, and as a dealer I was in a position to really enjoy this fantastic new bike. My mildly hot-rodded '73 and '74 Z1s were fast, smooth, reliable and sounded sweet.

In early 1975, I won the amateur open class at Road Atlanta on my street Z, prompting me to buy '75 Z1B just for road racing. One thing led to another, and I found myself club racing seriously, then big-time AMA Superbike racing on that same old Z1. Along the way, my philosophy was to relentlessly address each shortcoming as it came up. What started as a stock amateur production class club racer, eventually turned into full-on pro class Superbike that could compete on the national stage.

At the end of the 1982 AMA season, the 1,000cc Superbike became a thing of the past as 750s were ushered in as the future. I tried unsuccessfully to sell the Z1 racer and all the spares. Some parts were sold, some were traded, some were lost, but the bulk of this thing I had invested so much time in stayed with me.

Retired from racing, but still street riding, I set out to raise a family and build a business (sound familiar?).

Twenty-five years later, the kids were successfully on their way and life had settled down. I began riding track days on my trusty Aprilia Tuono...what fun!

Some of my racing pals from the old days twisted my arm to go vintage racing. They didn't have to twist it too hard! My most recent road race was a quarter century earlier, but I felt I knew as much about racing a Z1 as anyone. However, I knew from spectating at these events that the heavyweight Superbike class was sprinkled with some well-developed racebikes and good riders, and that a mild effort would not succeed.

What made this restoration project different than others is that I wanted to remain authentic, but it had to be a race worthy and competitive bike when completed.

First I gathered all the Z1 stuff, disassemble all the calipers, engine block and other chunks, then took an inventory of pieces and parts for the restoration. Several things were missing and many things aged beyond usefulness. By using the Internet and the motorcycle underground, I found much of what was lacking.

Thirty years ago, I was inventing and fabricating every little thing, such as an oil pan baffle to keep the pump from cavitating under hard acceleration, racing ignition, and a manual cam chain tensioner. There were few off the shelf racing bits available at the time. Since then, the venerable Z1 had become the staple of the drag-racing set, and many specialty racing parts are now easy to buy. Thank goodness.

(One comical side note: Many of the special parts were in four big boxes in my garage, but a few instrumental pieces were missing. It took considerable effort and expense to replace them. Once the final bits were gathered, I stumbled upon the fifth big box that had all the things I worked so hard to get. Bummer!)

Finally, it's fall 2006 and I had everything needed to put the project together and begin the race tuning.

Staying true to the past, honoring today's vintage racing rules, and being competitive all at the same time was tough. I braced the frame, adapted and re-valved an '86 ZX1000 front end, retrofitted SV650 wheels with modern floating rotors, and hand built the exhaust system from commercially available mandrel bent tubing. Modern wheels and rotors are OK, but they must use vintage calipers and modest-width rims.

The "high-tech in 1982" Works Performance rear shocks looked good but weren't fresh enough for serious racing. I was pleased to hear from Works that they could gut my original shocks and transplant modern parts to make them work. When they received my old shocks the story changed: too corroded to work, must buy new ones. Oh well.

Onto the fun stuff, the engine!

Two of my friends back then were high school shop teachers, with a motorcycle repair lab on their campus. Dyno!

With the time, money and technology available in 1980, I was able to squeeze 100 rear-wheel horsepower (RWHP) from the 1,015cc engine and stay within the rules. Today is no different, I would need a lot of dyno time for the first few months to get things right. A bulk agreement for dyno use from a local speed shop was made.

Modern oils, ceramics, metallurgy and the wisdom gained over time made it possible for me to build and tune the modern version of my Z1 to 126 RWHP! Wow, I could have used 126 HP in 1978!

I describe this bike as "the leading edge of yesterday's technology."

If you want to see it up close and in operation, the Z1 and I will be at the Mid-Ohio Sports Car Course this July 22-24 for AMA Vintage Motorcycle Days featuring Kawasaki, Marque of the Year.

Enjoy the above photos from the old days, the restoration, and recent pics as well.

Come by the road race paddock and take a look at this old restored war horse -- the bike I mean!


Arthur Kowitz