So I have a few Chinese brand engines laying around. I did some measuring and have decided that it appears the cases are the same dimension between the 50cc, 70cc, and 110cc (Head bolt pattern, case width, etc.) I am assuming that the only real difference between any of them is the bore and stroke. So I was thinking of trying to take the crank, connecting rod, piston, jug, and head from a 110cc and putting them into a 70cc that has a 4 speed trans. Has anyone here attempted anything like this or know if there are any other differences in the internals that I am unaware of? I have a 70cc dirt bike that I want to turn into a 110cc but I don't have a 110cc with a trans that would work in a dirt bike, mainly cause I don't want reverse on it. I am not afraid of tearing these engines apart and reassembling them in a Frankenstein fashion.

 

Be careful, they may look the same, but often have slight differences. I needed a starter motor for one a while back and noticed those sold for 70s were different to those for 110s. On examination of the on-line sellers dimensions, the hole centres for mounting bolts were different.

 

Thanks! Yeah I figured there might be a few subtle differences but the cases seem to have the same bolt pattern. I should probably take pictures and video for documentation purposes.