Small Engines (Lawn Mowers, etc.): B&S 18hp L-head twin, cast iron block, boxer engine

Question
Hello Eric,

I just got an 18hp opposed twin which sure looks like an Onan boxer engine except the cast iron block. Everything appears to OK, I can just imagine you know where most this engine troubles are. I would appreciate you sharing what the high-failure items are and what to be watching out for.

I'm planning on a propane/gasoline conversion is this engine a good candidate? Thanks retired computer E.T.

Answer
Is your setup to run on one type of fuel?  I have seen conversions but usually the conversion only allows one fuel type.

How old is the engine and what do you plan on using it for?  You can tell the engine age by looking at the first two digits of the code number.  As for the application, I have seen L head twins in everything from riding mowers, generators, pumps to go-karts.  

Eric