RE: engine question
buy the replacement parts. but get the pro 24.7 parts. ask your guy at your lhs. the pro has a diffeent cylinder and i think a different crankshaft but same size crankcase. the parts should work. you will get more power.
or if i am totally wrong, you can just get a new piston and sleeve from hobbypeople.net. the 24.7 is a great engine.