Re: 80cc powerking motor 30km/h top speed
sounds like you broke it in pretty rich.
here's what i'd do:
first, take the head off. the top of your piston's probably all black with carbon deposits. clean all that off with some carb cleaner and a soft toothbrush. you don't wanna use anything abrasive, 'cause it'll mess up your cylinder walls. clean the top of your head, too. get all that gunk outta there.
second, clean your plug. or get a new one. use a file, and taper the tip of it a little bit. make sure it's gapped right (mine's at .28 -.30)
third, move the clip on your needle up a notch.
make sure your air filter's clean and reassemble all of it.
that should work.
after your first ride, while the motor's still hot, VERY GENTLY tighten your head bolts a little. just a little. this helps to seat them and keep them tight.
after a few rides, check your plug again. if it's still black, go up another notch.
during break in, your motor is just getting soaked with oil, and the carbon deposits build up. if you don't clean it up, it'll never run good.