WHEN TURBOS WERE KINGS
The turbocharger – a simple device that makes a big difference, but motorcycle designers only flirted with them briefly. It might help to understand the spectacularly rapid rise and fall without a trace of the turbo kings from all four of the Japanese giants. In order of appearance they were the Honda CX500 (1981, followed by the 650 in 1983), Yamaha’s XJ650 (1982), Suzuki’s XN85 (1982) and Kawasaki’s GPz750 (1983).
In reality, they lasted barely two years and were never revisited as a catalogue item. Turbocharging is one of those terribly attractive ideas from an engineering standpoint. You use the energy in waste gas from the powerplant to spin a turbine that pressurises the intake, which in turn assists the engine in making a lot more power. Something for almost nothing. The reality is, of course, more complex.
You’d think it’s an idea just made for motorcycles but, due to a mix of factors, the idea comprehensively bombed.
BUYING A TURBO
Contrary to popular opinion, the turbo unit itself is not an issue as there are numerous businesses out there that can rebuild one, just as they can rebuild an engine. The real issue for the would-be restorer is getting cosmetic parts including panels and original mufflers.
Electronics also need to be in good working order as replacement could turn out to be a real nightmare.
The GPz is probably the least-intimidating bike of the four to rebuild, while the CX500 could easily end up being the most interesting and valuable.
Most of these machines were sold in the US. Local sales were very low, and the Kawasaki seems to have won the popularity contest here. Even so, we’re only talking about a few units.
Once sorted, running costs should be no great issue. They have plenty of straight-line performance, but you need to remember skinny tyres and brakes over a quarter of a century old in design have severe limitations. So cornering and stopping are going to be ‘entertaining’ by current standards.
Prices are not especially high, but beware anything that isn’t running and close to complete as you could easily find restoration costs easily outstrip the purchase price.
THE BIG GUNS
Why didn’t motorcycle makers just whack a turbo on the 1100s and 1000s of the day? Well, they did, sort of. Kawasaki USA famously had a go in small volume with the Z1R TC (1978-79 – years before the factory bikes), matching an aftermarket ATP kit to the production Z1R and making 500 units.
Running relatively low boost from a set-up matched to a 38mm Facet pumper carb, it was reported to be surprisingly good, though low-volume production tends to be reviewed far more gently than mass-produced. It scored a blistering quarter-mile time of 10.9 seconds with a terminal of 209km/h.
The truth is the chassis and tyres of the late ’70s and early ’80s simply weren’t up to the sort of power a full-blown big-bore project could produce – say 150 or more horses – at least not at a level where the manufacturer would be prepared to send it out into the showrooms. As for warranty, that would have just been a grenade looking for somewhere to explode.
There were lots of interesting experiments over the years, however, from the factories and their national distributors.
Yamaha Australia was reported to have had a go with the XS1100 four. The white-knuckled test pilot, a local top-level road racer, apparently cut it loose on a freeway late at night and reported he was using the entire road by the time the monster was up to full boost. Not something you’d let the punters loose on, no matter how late at night…