Originally Posted by token

What ever you can fit in there will work sort of..... Remember that these are designed for the amount of power put out by the engine they include so going to a more powerful engine may require replacement of the stock plastic gears in the tranny. You may want to replace them with Robinson steel gears. You would probley wanna stick with something that is pull start or roto start cause like Domit said, cranks are different and i would not put a RACE engine in my bash toy........