Jerry, I have a GS40 that I converted to CL after running it in RC planes for some time.  It seems to be very good; tons of power.  It won't shift from 4 to 2, but runs real steady at a wet 2.  It needs a tongue muffler that will attach directly to the engine, in order to eliminate that stupid and heavy ST exhaust set up.  It's a nice engine for $50 plus the cost of the venturi, NVA, and tongue muffler.   Glen