TOPIC:

I've just bought a KZ650 which runs fine but there seems to be a problem with the starter motor, it turns once then stops, can anyone tell me if this is a typical problem and how I might cure it

Is it the starter motor or the engine that turns onces and then stops? If it's the engine, then the likely culprit is the starter clutch located on the secondary shaft inside the engine. Replacing it requires pulling off the exhaust, pan, clutch and then removing the secondary shaft and replacing the "one-way" assembly (it comes with the machined piece, rollers, pins, and springs). It's not a trivial job, but it's not extremely difficult either.

If the starter motor is stalling out, it can be removed quite easily. Most likely there is a brush hanging up.

Typically, a worn starter clutch makes quite a bit of noise when trying to start the engine because it's slipping under load. Otherwise it's quiet. Is there a squealing/grinding noise?

Most KZ650 riders I know just kick start
their bikes.

Welcome Pete.

My starter's been good for 30 years. The starting button might need some work as I have to wiggle it a bit sometimes.
Glad it works too as the rear set pegs I've installed are in the way of the kick starter.