my 2001 yahama blaster blew up last year in autgust. i had the motor sent to the atv shop bored 0.20 over new bearings seals case piston rings carb rebuild kit and it runs excellent but it when it is started it sitcks wide open and will not slow down. I have to either dump the clutch or shut it off and hope it dies out. Some times it is like a dieasle and fires under compression i can shut the key and the main engine switch off and it will still keep running for a 10-15 seconds. I have tried everything i have loosened the throttle cables had the tors unit on top tore apart by a atv mechanice i also have had tried different reeds out of other blasters. The throttle will stick wide open but you can still move the slide if you hit the trhottle when it is stuck it doesnt do anything. !!!!!!!!!!! i am ready to send this thing to the bone yard

 

My guess maybe something with the Carb. Check That Out. How high u get when u dump that clutch lol

 

Do a leak down test, it sounds like you have an air leak.

 

I would have to agree with daputz on this one .

I had the same problem , check for air leaks , it can be a combination of the two being the leak and the throttle cable.
Blasters are known for that and , yes they are fustrating but hold your cool because there easy to fix, make sure you check all your top motor bolts first and work from there.
Good luck.

 

spray starter fluid around and if theres an air leak the engine will die.