Looking Beyond Power Gains to Shave Time in Drag Racing: KAWASAKI Z1000 Custom by Class4 Engineering

Class4 Engineering's Z1000

This Kawasaki KZ1000, a 1977 A1 model, looks every bit the street custom. It’s the owner’s daily motorcycle , but as you can see, the exterior has been updated to MK.II styling.

“This Z is one of the bikes we help prepare for JD-STER drag race competition,” explains Masahiko Yokota, head of Class4 Engineering. “The owner is now in his eighth season since his first JD entry. At first, he raced his street bike more or less as it was—a 1075cc KZ with just a Stage 1 cam, really more of a mountain road setup than a drag bike. But with the aim of stepping up to the Vintage Superbike (VSB) class, it was upgraded to 1200cc with a much higher-lift cam. This is now its second season in that form.”

That said, it’s still mainly used for street riding. Only when entering JD-STER does it switch into race setup, fitted with a Sidewinder exhaust and Ohlins drag shocks reworked by U.S.-based M2 Shocks to lower the rear. With this setup, the bike has managed top finishes in the VSB class and has been steadily improving its times.

“In drag racing, people tend to focus only on engine power. But with this Z, one of the themes is to challenge stronger rivals through chassis work instead. Compared to engine tuning, chassis setup costs less to build and is cheaper to maintain. Engines need to be opened up and checked regularly, while once the chassis is properly adjusted, running costs stay low. And when the setup is right, it gives the bike more stability. That makes it especially well-suited for tournament-style drag racing, where concentration in short, decisive rounds is key,” says Yokota.

To further explore the benefits of chassis tuning, Yokota also built a monoshock MK.II for himself. The data gathered from that project will eventually feed back into this Z1000, leading to even quicker times. For Z enthusiasts, it’s a fascinating challenge.

Handlebar

The bike is fitted with a Stack tachometer and a Yoshimura digital temperature meter. The brake master cylinder is from Nissin, and the clutch has been converted to a hydraulic system by GALE SPEED. A tether kill switch is also installed for safety.

Engine

The engine is based on a 1977 Z1000 (70mm × 66mm) and has been big bored to 1197cc using 76mm pistons from CP-Carrillo. The head has been converted to a twin-plug setup, and Web cams are installed with 0.435-inch lift on the intake and 0.395-inch lift on the exhaust. Standard Z1000J valves were enlarged by 1mm each (Intake: 31mm, Exhaust: 37mm).

It’s fitted with a 36mm TMR carburetor and a Vance & Hines Sidewinder exhaust. The exterior uses stock Mk.II parts and repainted.

Chassis

The front forks are from a Yamaha XJR1300 (43mm). For racing, the front can be shortened using tie-down straps to adjust the bike’s stance, as shown in the photos.

The wheels are a mix of models: the front is from an XJR1200 (3.50-17) and the rear from a 1989 GSX-R750 (5.50-17). Tires are a Shinko Stealth on the front and a drag-specific Hookup on the rear.

The swingarm is from a Zephyr 1100, while the rear shocks are a special setup based on Harley-Davidson units, modified by M2 Shocks for altered length and damping characteristics.

Gallery

Specifications

About Class4 Engineering

The price of the billet parts handled by Class4 Engineering are reasonable, and you can readily customize your beloved motorcycle. Their stylish parts are popular among Japanese fans as well as its homeland fans.

Class4 Engineering brand page

Original Source of this Article

Heritage & Legends