Can you replace a crankcase cover with one from another block?

Hey Guys,


1987 Yamaha Pro50


I noticed a leak of two stroke oil on the crank case cover (intake side). Wiped it off...and it came back. I bought the motor second hand. The guy had rebuilt it because it had locked up. I sanded down the paint in the area and can't see any cracks. I'm going to pull the front cover for closer inspection and I was looking at replacing it with a good cover but I've come to find through research there is some debate that case halves are/are not interchangeable due to them being line bored for a precision fit.


Any insight on this? Has anyone thrown together different case halves with success?

Yes they are a precision fit and line bored.-----You take your chances if you want to use another cover.-----Best to take it apart and see what is wrong first.-----Those joints rarely leak so something is wrong here !!

racerone said:

Yes they are a precision fit and line bored.-----You take your chances if you want to use another cover.-----Best to take it apart and see what is wrong first.-----Those joints rarely leak so something is wrong here !!

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My best guess at this point is when the motor locked up, a rod damaged the side of the case and it wasn’t caught/repaired upon rebuild. We shall see.