Originally Posted by Greg58
My o.p. cruiser is over 5 years old and has a couple thousand miles on it, its a aluminum frame. The 48cc engines have little to no vibration, that may be why I've not had problems. Or it could be that running only 25 to 26 puts less strain on the frame.
It's the 49cc lack of vibration that makes your story not only possible, but typical. The 49cc motors are MUCH easier on frames and parts due entirely to better overall crank balance and smaller rotating mass.
The 66cc has a high frequency vibration cycle that is BRUTAL on anything flexible and it will bring out the weak spots in any assembly.
Work hardening is the cause of 99% of chinadoll induced failures in fenders, frames, whatever, and it's due almost entirely to the poor crank balance of the generic chinadoll.
The newer 40mm stroke crank pk80's also have much better balanced cranks with markedly less vibration.
Flex almost ANY metal back and forth 200 times a minute and things WILL break.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.