Ralph...... Now this is a loaded question if I ever saw one but I'll go ahead and bite anyhow. I have an OS 120 Gemini 120 Twin, that was converted from 2 OS 60 four stroke engines. Pretty good engine for what it is. OH! OH! Bet you were referring to "Gas" conversions. Sorry..........In that case I'll take a Zenoah G62 "lite," over anything else in it's class. Bob Laine