Starter Motor Gone???

Having problems with my cabby, when i first got it the start motor seemed to struggle to turn the engine over so i took if off cleaned it up
with some contact cleaner and it was ok for a few weeks.
Its now doing it again could it be choke up with clutch dust?? do i a)clean it again (b) buy a new one or could it be © bad earth???
Just wanna know your views before i shell out a tonne for a new one!


Cheers

Jamie

Poor battery ?