ORIGINAL: tunes079
I would recomend a O.S. 46AX two stroke for a trainer due to its power, ease of use, and most importantly, the price. Now if you have your heart set on a fourstroke, I would go with a saito .56. It has good power
and should be very similar in weight as your average 40 size twostroke.
I'll second that advice. The 46AX is a VERY strong engine. Easy to tune and affordable. I have a Saito .56 on a low wing sport plane designed for a 40 to 46 two stroke. It flys it very well with plenty of power, sweet idle, and that wonderful 4 stroke sound. And it didn't mess up the weight and balance .