SV730 low compression on 1 cyl.
 

have a SV730 horizontal stroke ohv twin with 150psi on one cylinder and 110 on the other. could this be a valve seat problem? 600 hours on engine.

it could be, but it could be weak rings or a leaking head gasket. you could put a leak down tester on it or use a rubber tip blow gun to put some air psi into the cyl. see or listen to where it leaks out.