My engine runs very high rev and chain drops then dies! HELP ME!

[Babykangaz]

Hello everyone,
today i got my first motored bike!
it was all well until the afternoon of riding it around..
at high speeds, the engine suddenly revs up very high, and then the chain drops and the engine dies..
also when i stop and hold the clutch down it revs extremely high when its completly stopped!

please help me.

And the bike is also a chopper/2nd hand 66cc.
any other questions just ask me!

 

[HeadSmess]

um....

throttle sticking?

major air leak in the intake somewhere...

chain sounds a tad on the loose side...?

 

[Babykangaz]

Throttle not sticking.. and the chain seems very tight..
how can i check for a air leak?

 

[Skyliner70cc]

idle speed set too high.

 

[Babykangaz]

can you please guide me through how to set the idle speed?
i cant even get it to idle properly.
thankyou