Originally Posted by surferscha
I recently swapped out a motor on my friends motorized bike because his motor needs a top end (cylinder, piston and rings). I want to rebuild the engine but my friend does not know whether it is a 49 cc or 68 cc. Is thier any way to tell by measureing the bore or whatever? Or are the cylinder and piston kits interchangeable for the 49 cc and 68 cc?
Welcome to the forum.
The 50 cc and 66 cc / 80 are not interchangeable.
It's easy to tell the difference if the motor is apart.
There are slightly different motors though so the replacement piston and cylinder have to be the same.
This pic will help you figure it out with a little measuring.