with all the problems with these small engines from china. why not get an os and avoid the problem in the first place. they just came out with a 22 cc gas engine. they cost alittle more but run very good. any engine less than 22 cc is not worth it anyway IMHO. if you can't offord nitro for a .40.50 maybe you shouldn't be flying. i like small gas engines but i think they have a limit. the weight of another battery pack plus the cdi is just not feasable to me. anything besides an xcell ignition is pretty much junk anyway. don't waste you time and money on junk gas engines, buy something good. besides you risk your plane and electronics to boot, just to save a few bucks.............GEETER