1978 Kawasaki Z1R-TC: Turbo Power

Before the 1980s turbo wars came the 1978 Kawasaki Z1R-TC, the first production turbocharged motorcycle of them all.


| January/February 2013



1978 Kawasaki Z1R-TC

The appeal of turbo power launched a brace of unlikely motorcycles, as well, including the Honda CX500/650 Turbo, the Kawasaki GPz750 Turbo, the Yamaha XJ650 Seca Turbo and Suzuki’s XN85. Almost forgotten in the rush was the first turbo bike, the 1978 Kawasaki Z1R-TC.

Photo By Corey Levenson

1978 Kawasaki Z1R-TC
Claimed power
: 130hp @ 8,500rpm
Top speed: 135mph (period test)
Engine: 1,016cc air-cooled turbocharged DOHC inline four, 70mm x 66mm bore and stroke, 8.7:1 compression ratio
Weight (wet): 560lb (255kg)
Fuel capacity/MPG: 3.4gal (12.9ltr)/35-45mpg (est.)
Price then/now: $4,995/$12,000-$18,000

Notoriously reticent about horsepower figures, the Rolls-Royce company adopted a snooty retort to inquiries about the output of its automobile engines: “Sufficient,” was all they would say. But when the pavement-bending Bentley Mulsanne Turbo first rolled out of the Derby Works in 1982, the stock answer would no longer do. It became: “Sufficient — plus 50 percent.”

The 50 percent came from a Garrett AiResearch turbocharger bolted on to R-R’s 412ci V8. The prestige car maker wasn’t alone in its approach to instant horsepower, and the 1980s became the turbo decade. Saab, Volvo and others adopted turbos to pep up their 4-cylinder engines, and many American automakers used turbocharged V6s to replace gas-guzzling V8s as a way of meeting fuel consumption targets.

The appeal of turbo power launched a brace of unlikely motorcycles as well, including the Honda CX500/650 Turbo, the Kawasaki GPz750 Turbo, the Yamaha XJ650 Seca Turbo and Suzuki’s XN85. Almost forgotten in the rush was the first turbo bike, the 1978 Kawasaki Z1R-TC.

Boost

The first widespread use of turbochargers was to boost the performance of high-altitude World War II aircraft like the B-17 Flying Fortress and the P-38 Lightning and P-47 Thunderbolt fighters. In 1978, Kawasaki’s flagship 1,000cc model needed a boost. The 1970s had become a game-changing decade in motorcycle development, and Kawasaki was being left behind. In spite of leapfrogging Honda’s CB750 with the double overhead cam 903cc Z1, Kawasaki’s big bike development had stalled in mid-decade.

Though revolutionary when introduced, the Z1 wasn’t perfect. The mild steel double cradle frame flexed under load, the 36mm forks were under-specified, and the rear suspension was over-sprung and under-damped. To lighten the steering, Kawasaki’s engineers gave the Z1 a sharp, 26-degree steering rake, but it came at a price; sudden direction changes would induce weaves, which, combined with the lack of trail, could quickly get out of hand. Neither was the single disc/drum brake combo up to hauling 530 pounds of motorcycle down from 125mph.

When the Suzuki GS750 arrived in 1977, Kawasaki countered with the triple disc-brake KZ1000. It looked cooler, and maybe stopped better, but the extra 100ccs produced little if any extra power, and the flexy frame remained. The liter-class still set the performance benchmark, but with the GPz1100 a couple of years away, Kawi’s Z-bike needed a makeover to extend its life.

Enter the Z1R

The Z1R was more a styling exercise than a new motorcycle. The R-bike featured a handlebar fairing — a first on a Japanese sport bike — the squared-off lines of which were echoed in the “coffin” gas tank, triangular side panels and swooping tailpiece, all finished in ice-blue metallic paint. You certainly couldn’t miss it — which was the idea.

Underneath the bodywork the KZ1000 engine (now with 28mm versus 26mm carbs) went into the same flexy frame and exhaled through a new 4-into-1 exhaust. Claimed horsepower was up to 90 at the crank (though period dyno tests failed to find much more than the stock KZ). New cast alloy wheels were 18-inch front and rear (the KZ1000’s wire front wheel was 19-inch), and drilled triple discs handled slowing the big blue bike.

It was when reviewers actually rode the Z1R that the wheels started to come off — off the ground, anyway. Although it had extra gusseting, the R bike used essentially the same frame as the earlier, lighter Z1. The smaller front wheel reduced the marginal trail even more, making the R even livelier than its predecessor, plus it had stiffer rear springs and increased damping. “It doesn’t roll over bumps: it bounces from crest to crest,” wrote Cycle Guide in a period review. The same magazine found the handling “less than road racer precise thanks to numerous rubbery frame tubes.”

So Kawasaki had created a high-powered pogo stick with suspect handling. Probably the last thing it needed was more power, and a lot more power at that ...

Pumping iron — the Kawasaki Z1R-TC

The Z1R-TC idea was the brainchild of former Kawasaki executive Alan Masek. Masek had big plans for his newly-formed Turbo Cycle Company, and noted that slow Z1R sales meant there were surplus bikes in the supply chain. At the same time, Kawasaki needed something to wow the market while waiting for the GPz1100 to arrive.

It was the perfect opportunity for Big Green: Masek would take stock Z1Rs, fit an American Turbo Pak compressor and its ancillaries, then feed the converted bikes back into the Kawasaki dealer network. Any regulatory or liability issues could be diverted at TCC, while Kawi reaped the benefits of winning the horsepower war.

For the first batch of 250 or so Z1R Turbos, TCC simply replaced the header pipes with a new cylindrical exhaust collector (known to TC fans as “the log”) to feed the ATP turbo unit, added an adjustable wastegate, installed a new open exhaust to eliminate back-pressure in the turbo and added a boost gauge to the dashboard. Apart from TC decals on the side panels — and a notice that the Z1R-TC should only be used by experienced riders — that was pretty much it. A supplied list of do’s and don’ts also included a warning to owners not to attempt to increase boost by tampering with the wastegate setting, which was a bit like telling a dog not to chew a bone. Every TC buyer was required to sign a liability waiver, too. What could  possibly go wrong?

For starters, the Z1R-TCs offered to the press for testing were specially prepared. The engines had been stripped so the built-up crankshafts could be welded to prevent twisting while the valve and clutch springs were replaced with stronger items. None of these modifications were standard on “production” bikes, though they could be special ordered at extra cost.

Neither was the engine fitted with a rev limiter, an innovation that would have to wait until electronic ignition arrived. This was a potential problem on the TC, considering a turbocharger creates what is essentially a positive feedback loop. In a normally-aspirated engine, gas-flow efficiency typically limits the revs the engine will achieve. But with the throttle wide open, a compressor-fed engine will continue to spin up until the valves float or start hitting the pistons. Catastrophic failure follows, often caused just by missing a gear. Not surprisingly, the TC was sold without a powertrain warranty, and buyers had to sign off to that effect, with a witness! Further, the TC’s performance capability far exceeded the limitations of the stock Z1-R chassis on anything but a billiard-table-smooth drag strip. And the TC listed at  $1,400 more than the stock Z1R’s already hefty $3,695 sticker.

James Fuller
1/18/2013 8:53:42 PM

I had a gpz 750 that i bought new. it was hard on the head gaskets. but it was a fast bike.






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