It started in 1982 with the Honda CX500 turbo, but it wasn't long before the other manufacturers showcased their own vision of a middleweight with literbike performance. The reality didn't live up to the fantasy, but that didn't stop Suzuki from also giving us the XN85, Yamaha building the XJ650T and Honda upping the CX's capacity to 650cc. The best was saved for last-Kawasaki's late-entry GPz750 Turbo was widely accepted as the best of the big four turbos. So what if Kawi gave it another shot for 2010?
With a claimed power output of 100 HP, the original 1984 air-cooled 750 engine may sound sufficient, but it was hampered by a hefty 500-pound weight penalty. The other issue was Kawasaki's own GPZ900 launched in the same year. It made more power, weighed less and ran rings around it on the road. Our engine would be based on the grunt-laden 636cc motor. With fuel injection from the 2010 ZX-6R (but using the original and essential DFI logo), a thicker head gasket to lower compression to safe levels and a Garrett turbo running a modest 6 PSI of boost, we can still expect a reliable 50 percent increase in power-that's 150 real HP with the stock crank, pistons and rods. With such low boost, perfect fuelling and tweaked ignition, an intercooler wouldn't be needed-not that there's any room left to mount one.
Due to the extra power, we've strengthened our 2010 ZX-6R alloy beam frame, but retained the wheels, brakes and suspension. Kawasaki got plenty right with the latest ZX-6R, and the Showa Big Piston forks take some beating. The swingarm is fashioned after the Aprilia Cube's, itself no stranger to monstrous power delivery. Overall, weight is no more than a standard ZX-6R. Despite the extra bulk of the turbo kit we've lost a few pounds by junking the massive silencer and required pipework.
The turbo works best when it's fed plenty of air, which is why our oversized airbox takes up the space where the fuel tank would normally be; the actual tank is under the seat, but there's still enough room in a cubby hole behind the butt stop for a disc lock and pack of smokes. The central vent in the nose provides ram-air. Because we're going to be abusing the extra performance, we've widened the top cowl for more wind protection and lifted headlights from the ZX-14. Vents channel cooling air to the turbo in the bellypan while ducts draw hot air away. Now let's go literbike hunting on our "little 600."