my sons bike died one day and wouldn't start...thought it was was flooded and checked the float height..it was fine...cleaned it all out and didn't help...it will start with the choke on, allow me to put it the closed choked if it is warm enough. however it revs so high that the quad wants to take off...adjusting the idle screw or fuel screw does not help...spark plug was black and dry on the top but wet on the bottom and stunk like gas...cant find any air leaks....anyone have any ideas what else to check

 

Sounds like it could be a crank seal.
I'd check the compression tho.

 

how would a crank seal cause a vacuum leak?

 

Ooops...I am presuming you have a 2 stroke motor.
If so, a seal leak sucks air in leaning it out thus a higher uncontrolable idle.
The sustained choke to stay running points toward the seal and/or compression.

 

Does sound like a vac leak tho. Make sure you put the carb to head intake on correctly. Easy to put on incorrect.

 

Check your throttle cable as well.. Sometimes they get moved and it will cause the cable to tighten up and lift the slide increasing the idle and making it hard to start.