All Chinese happytime motor kits have NO quality control.
They are all crap.
Only the DEALER that you bought it from can help you if you have trouble.
There are very few that will help you after the sale.
It has been too long for me to recommend a dealer.
I do not build happytimes anymore.
Count on everything from the rear sprocket to the twist throttle and everything in between to be off in quality.
How expensive would a new motor for the scooter be??
a complete 50 cc engine with transmission for $300.00
Hooper Imports Experts on Chinese Motorcycles and Parts, Engines - Product Detail
A 70 cc for $300.00 as well .
Count on spending many frustrating hours replacing all the inferior quality parts until magically one day they quit breaking for a while NO kidding.
Happytimes are a hobby only.
Look at a thats dax ora BMP friction drive if it doesnt rain too much where you live.
Without the loss of friction between the drive roller and the back tire, when it rains, they will be a much better option on a motorized bicycle.
FYI I used to buy parts from a very well known Chinese scooter importer.
All of a sudden they began to fail .
I began to really carefully inspect the replacements this jerk was selling me.
They were used returns from that the factory was sending him .
He did not want to be stuck with them so he was selling them as new.
Buyer beware when dealing with Chinese imported stuff.