engine stuck at full throttle

[cricket33]

I just got a 2002 buell blast yesterday. Today when I was leaving my house and pulled out of my driveway, I accelerated quickly to get up to speed with the traffic. The throttle seems to have gotten stuck at full throttle and I couldn't get it to throttle down. I pulled in the clutch and pulled over and shut the bike down so I wouldn't blow the engine or cause any other damage. The cable doesn't seem to be stuck as I turned the throttle back and forth and also pulled on the cable down by the carb. I turned the bike back on and the throttle instantly went back up to full throttle. Any suggestions to what it could be? Any help would be appreciated. Thanks

Tim

 

[XRorXB]

Congratulations on the Blast. It could be a number of things.

You mentioned pulling the cable down by the carb. Did you see both push/pull cables moving there? What about the throttle cam at the carb? You will be able to tell a lot if you can remove the air filter and stick your finger inside the carburetor body and feel the throttle plate move both directions (you may need E.T. fingers).

There could be something stuck between the throttle plate and body inside the carb, or the throttle plate could have come loose from the shaft (happened to me once on a different bike).

Also, check your Throttle Position Sensor connection, and Idle adjustment screw to be sure nothing is jammed in there preventing the throttle from fully closing.

 

[cricket33]

The throttle plate does move. How much should it move. Should it be able to be totally vertical? It moves prob 10 degrees in both directions from the horizontal position.

 

[XRorXB]

Hi Tim, in order for the engine to idle, the throttle plate inside the carb will be vertical so as to close the passage of most all air entering the engine.
Likewise, with the throttle grip fully twisted (full throttle), the throttle plate inside will be horizontal. So you should have near 90 degrees of travel.

Both the throttle grip and throttle plate must snap closed when the grip is released from full or part throttle. If they don't, check the things mentioned above.
Also, *check the spring that winds around the throttle cam outside the carb, where the cables attach. Is the spring doing its job? There is also a vacuum piston in this carb that in theory could get stuck open - it should be blocking your finger from feeling the throttle plate (you can lift it up out of the way) - but assuming your throttle plate works properly, I would expect that if the piston were stuck open, it would hardly even idle due to the main jet being wide open.

Just reply back with what you found for each of these checks.