okay, here is the deal. iam helping a friend with a carb swap. weve got the motor in and it runs great, but after the engine gets hot after running around it will not turn over. ( once you kill it after getting hot it will not turn over).
if the engine is cold it turns over easy. the battery stays at about 13.5v.
(after getting hot) if you turn the starter over it goes from 13.5v to 4.5v
battery and the altenator are new.
could this just be a bad starter???

 

Is it a factory starter? If so, the factory direct drive units aren't exactly known for being the best in the world at hot starting. Might be time for a good gear reduction starter.