Ever since fitting my RB25 it starts fine when cold (when the battery is charged that is) then when it's been running for 10 mins or more and switch it off it won't start again. So I could drive from my house to the petrol station and it won't start again. Engine turns really slowly as if the battery is flat. Once it's cooled down enough it starts fine again and engine turns over quickly enough, so it's not the battery at fault.
Any ideas? Earth problem or time for a new starter motor?