[Drifter2]

Thanks Kevan,
Ironically the motor in question was new and has never had a pinion fitted. 
I should have returned it to the shop I bought it from, but was too busy at the time and forgot later on.

[Kevan]

Ah, if it's a new motor and the brushes and comm are still new then a good clean out with contact cleaner may well resurrect it

...don't oil the endbell bearing