100cc started rattling now wont run please help

[Terryosw]

Hi I installed a 100cc BBK and it ran good for a month and it sounded like the piston was nocking on take off and then stopped when riding and then it started rattling on going up hill the next day took it for a short ride pulled up in my driveway it started rattling and pinging bad so then it cut off so then I tried to start it and no good. So now it will turn over but will not run I've checked everything even put the original 50cc motor back on and it still won't fire up if anyone can please help? Thanks