my moped is hissing

i dont know what is wrong with my moped, it is an adly thunder bike TB-50 and when i rev it up on the stand it tops out at around 4000RPM and begins hissing and the tach goes up and down. it will not get enough power to run on the ground. when it hisses it blows a crap load of black stuff out the muffler. i would greatly appreciate some help on this.


my moped is hissing

i should prolly also mention that it usually runs at about 35 mph at 7500RPM

Re: my moped is hissing

Is that a 2-stroke scooter?

When did this start happening and what changed during that time? Did you dump some of last summer's fuel in the tank, adding oil to old fuel that already had oil added?

All the smoke makes it seems like a carburation or fuel related thing. Try a brand new sparkplug and a fresh batch of fuel.

And try the forums at

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