Another bump.

I've been doing some reading up on single-phase AC motors and my symptons are classic for a starter ciruit failure. From what I've read this can be down to three things (assuming that the motor isn't plain and simple gummed up somehow).

1) Starter capacitor
2) Centrifugal switch
3) Starter windings

(1) Is a simple "replace it and see" job - relatively cheap. (2) Is a "motor apart and clean it" issue. (3) Would mean a new motor.

I don't think it's the starter windings because when it starts, it starts up fine. If the starter windings were fried I don't think it would start at all. The centrifugal switch gives a nice combination of an electrical fault that could be fixed by a swift kick so I think that's my prime suspect for now.

I'll have to take the motor out to look at the capacitor and check the connections so hopefully I'll be able to split the motor casing and get at / clean the switch at the same time.