Yamaha XJ650 Turbo, Part One - Classic Motorcycle Guide

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Yamaha XJ650 Turbo, Part One
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In 1982, Yamaha wanted their middleweights to go as fast as big bikes. So they, following the fashion of the times, slapped a turbo-charger on their XJ650. Was that wise, wonders Roger Prosper?

What makes a classic bike? Well, that depends on who you ask, doesn't it? Certain magazines seem to consider any bike built before the 1990s and still running as 'classics', but you'd be hard pressed to find many riders who would consider, say, a Hondamatic, a classic bike. Some bikes become classics despite their obvious shortcomings (Kawasaki triples for instance), while others become classics for their technological excellence (CB750 Honda). Others become classics due to their rarity (RE-5. Snigger), or for being recognised, too late perhaps, as being fine motorcycles to which no one gave a second glance when they were new.

Then there are bikes that seemingly fall into a black hole and are forgotten about soon after the initial hoopla surrounding their release fades away. I believe the XJ Turbo would fall into the latter category.

I should know, I own one of the bloody things.

1982 Yamaha XJ650 Turbo

The Turbo was Yamaha's effort in the short-lived turbo middleweight sportbike class that started with the introduction of the 1982 CX500T Honda. The CX was a technological tour-de-force, with computerised engine management, fuel injection, and 20psi of boost force-fed into... a CX500. It was a frenetic beast, with lots of gearshifting required to keep it on the boil. All four Japanese companies responded with boosted bikes of their own. The XN85 by Suzuki, reckoned to be the best handler (and the rarest and most valuable), was a mild performer. The GPz750 turbo from Kawasaki was the firebreather of the lot, with terrific speed and passable handling.

The XJ turbo, the flashiest of the group (arguably), was the simplest, with pressurized carburettors instead of the fuel injection and without the single shock rear suspension the others boasted. It was also the only shaft driven bike in the mix, as it used the shaft driven XJ series motor from the Maxim/Seca lines.

The performance of the initial batch of 1982 machines was somewhat tepid, and the bike's reputation suffered in comparison to the Honda, which had grown even more powerful, though a little simpler in CX650T guise.

Pictures were all small back in the 80's.

Yamaha's response was to include a 'Power Up Kit' on the 1983 XJ, which took its signal from the surge tank instead of the turbo itself to actuate the wastegate, which allowed boost to build a little higher than the original design.

There was also a restrictor (a washer) inserted into the wastegate to allow exhaust gases to bleed off a little more slowly into the right silencer, which only performed its duties when the wastegate actuated (this allowed condensation build up in the pipe, leading to its early demise).

This kit was available as a retrofit on 1982 bikes, and allowed the machine to reach about 12psi of boost, producing a fairly dramatic increase in performance. Yamaha claimed 90hp for the 1982 model in original low boost trim, so near on 100hp wouldn't be far off the mark (at the crank, of course).

Turbo stuff on eBay.co.uk

Although technically interesting, the turbo bikes were complex, heavy, and never quite delivered on the promise of litre-bike performance in a middleweight package. Most buyers concluded the available supersport 900s and 1000s were as powerful, less peaky, more reliable, and certainly cheaper. Normally aspirated middleweights available as little as three years later provided much better performance with much less techno-trickery and weight anyway, so the age of the turbo bike was short.

Few lamented their passing.

Next installment: Roger buys a cheap turbo. Ho ho!

XJ Turbo Titbits

Air-cooled 4-stroke DOHC 4-cylinder 653cc

Maximum power output: 90ps @ 9000rpm

Maximum torque: 8.33kg-m @ 7000rpm

Weight 230kg

'The aerodynamically designed full faring was the product of repeated world tunnel tests and employed much of the modelling technology and know-how Yamaha's marine division.' Yamaha Motor Co

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XJ Yamahas on eBay.co.uk

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