The smallest gasoline engines i have found are made by RCS and MVVS,RCS has a 140,and MVVS has a 160.Expect to pay around 400 bucks each for these engines.Both are very high quality engines however.One other engine is the ROTO 25,thats about it for smaller gasoline engines.RC Showcase handles the RCS engines and Morris Hobbies handles the MVVS.