I have a 94 Yamaha Blaster that i bought blown up and the cause of it was the oil injection pump died and seized the crank up. I just got it rebuilt with a new crank, Wiseco piston, and we removed the oil injection. Now the problem is that when i was running it (not that hard), the engine all of a sudden started reving higher without me giving it gas, and I had to kill it by stalling the motor. Now when ever it starts up it runs fine with the choke on but when you turn it off it slowly speeds up until it is screaming.

By the way the carb boot for the oil injection pump is on, and the tors system is removed.

Thanks.

 

One thing that could cause it to rev up is it's sucking air into the engine from somewhere. Most common places would be the carb boot or the base gasket. If that's the problem then it would do damage to the engine to run it like that for more than short periods.

 

I have tried spraying carb cleaner on the boot and the on every place it could suck in air and no reving at all.

 

Then this is the clue. It's not getting enough fuel unless the choke is on. It could be a dirty carb.

 

Thanks that is the main problem now. It turns out the idle adjustment on the TORS was turned way up. But now the the throttle cable sticks from a hole bunch of gunk from it sitting for 3 years before we got it in the TORS part on the carb and that's what causes it to not stop reving when you give it gas. Were going to replace that with a Mikuni cap and normal throttle cable. Thanks again.

 

Rumbaughman, when you get ready to change that throttle cable here is a diagram that might help. It is number 27 in the diagram.
OEM Parts

Good luck!