Bore and stroke 90cc sanyang farmers bike?

my friend has a 90cc sanyang farmers bike/super cub style bike. he really likes the way it looks, but complains that its always having engine problems no matter how many times he takes it to a mechanic. he’s considering getting rid of it and getting more of the standard looking floorboard scooter or moving up to a motorcyle.

i thought that maybe he could bore out and stroke the engine and suggested this to him as a way for him to keep the style that he likes.

a few questions:

  1. Is this possible with a 90cc sanyang engine? If so how much would it cost and where could it be done well? Also, what would the displacement be afterwards?

  2. If it’s not possible, could a new and potentially larger engine replace the current one?

  3. Ulitmately, would he be spending less money replacing the engine than he would buying a 2nd hand KTR or Wolf?



I bored my 90cc Honda (CS-90) for about 100 NT. Of course it was 1966 and prices have gone up a little since then. :smiley: :laughing:

Reboring the bike won’t necessarily make it any more reliable.
The unreliability is probably due to a number of factors.