1976-77年Yamaha SR500

The SR500, in true Japanese fashion, is a well engineered bike and in most places the toil of owning such a machine has been developed out: like leaks, dubious electrics and general lack of reliability. The machine is powered by an oversquare engine of 499CC with valve actuation by a single overhead camshaft. Essentially the same alloy unit as the XT off roader, the SR differs in valves size and port shape so is a little more potent. A maximum power figure of 33bhp at 65oorpm is not a lot for a 500, but peak torque is just over 281b ft at 55oorpm, and indeed the torque curve is remarkably flat from 2ooorpm to that figure. A five-speed gearbox is used and the bike will reach a top speed of just on 90mph in the highest of them. Fuel consumption is a bonus feature of such a bike and the SR500 should have no difficulty in producing an overall figure of well over 5ompg.

Rather than try to get a starter to turn over a 500CC cylinder with a 9:1 compression ratio, Yamaha decided to leave firing to a hefty rider, although they do make it as easy as possible. A compression release lever is fitted and the engine is turned carefully so that the piston is at the top of its stroke. A little window on the camshaft cover indicates when this point has been reached. The bike should then fire at the first kick. A vacuum automatic advance and retard system (like that of the XS1100) also helps. Also dispensing with an electric starter helps save weight as again a plus point of a single is that it is quite light. Dry weight of the machine is 3481b so a single disc brake at the front and drum rear ably stop it. Handling is good, too, and the narrow bike instils a lot of confidence in the rider to make full use of it.

The SR500 Yamaha may not suit everyone, but it does take the tears out of 'vintage biking'.

The indicator switch can be simply pressed inwards to override the unit.

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