Throttle stuck open

B

Bigdraggo

Registered
2001 busa

Went for a ride today, let it rip through a couple of gears and when I let go the throttle it continued to rev. I had to shut it off and pull over.


Tried staring the bike and it just revved to the red line

Checked the linkage and all seems to be in good order. Nothing getting stuck, the throttle snaps shut...

Any ideas, I couldn't figure it out...
 
The throttle plates on the bodies snap shut? May wanna check them. They could be damaged and getting stuck open
 
forgot to mention it has a velocity stage II kit in it, I was on the boost when i closed the throttle.

Pulled the TPS plug off, but still revs to red line
 
Glad you were able to get it slowed down safely.

This is a strange problem. I've only heard of it happening to somebody else one time before you. His problem turned out to be a ziptie on the throttle cables that worked its way into the wrong place. You say the throttle snaps back and closed when you let go of it, correct?
Have you physically looked at the throttle cables from end to end to see if anything is wrong with them?
 
Blanca Busa said:
Glad you were able to get it slowed down safely.

This is a strange problem. I've only heard of it happening to somebody else one time before you. His problem turned out to be a ziptie on the throttle cables that worked its way into the wrong place. You say the throttle snaps back and closed when you let go of it, correct?
Have you physically looked at the throttle cables from end to end to see if anything is wrong with them?
Click to expand...



Yes, for sure no issues with the cables. I took them off to be sure.
 
dadofthree said:
:dunno: somethings telling it to inject and fire
Click to expand...

Could it be a bad ECU??? So strange how it happened while on the gas. I just figured it was a linkage issue, but nope throttle bodies snap shut when you let go. I unpluged the power to the ECU and pluged it back in but the same issue...
 
the throttle body must be stuck open. if the blades are closed... it cannot rev. even if the ecu is telling the injectors more!

dis-assemble for inspection
 
Bigdraggo said:
I'll pull the plenum off this weekend. I thought the BOV would have stopped this...
Click to expand...

Popular misconception, the Blowoff valve does not open under high pressure, you could run 100psi of boost and the blow off valve will not open, also if you look at the direction of the bend in the blades it will indicate that the pressure cam from the engine side of them, likely due to a lean backfire or hitting the factory rev limiter.

Richard
 
2wicked said:
Popular misconception, the Blowoff valve does not open under high pressure, you could run 100psi of boost and the blow off valve will not open, also if you look at the direction of the bend in the blades it will indicate that the pressure cam from the engine side of them, likely due to a lean backfire or hitting the factory rev limiter.

Richard
Click to expand...

I to am guilty of this thought. I thought the bov was to open when you rolled off the throttle to prevent a compressor surge. I thought most would open at 14psi. Could you help remove my ignorance.

Sent from my GSB v3.6 ODEXed using Tapatalk
 
majestic12 said:
I to am guilty of this thought. I thought the bov was to open when you rolled off the throttle to prevent a compressor surge. I thought most would open at 14psi. Could you help remove my ignorance.

Sent from my GSB v3.6 ODEXed using Tapatalk
Click to expand...

Yes the blowoff valve will open when you close the throttle to prevent compressor surge, the blowoff valve works through pressure differential. If you have a 6 psi spring inn the blowoff valve, and you are running 10 psi, that means you have 10psi of boost on the face of the valve, and 10 psi on the diaphragm plus the 6 psi of spring pressure. So the blowoff vlave will never open under pressure, as it always has 6 psi of pressure on it above actual boost. But when you close the throttle, and your airbox has 10 psi in it and now on the underside of the throttle bodies (where the BOV should be connected) goes into a vacuum, your BOV will open, the vacuum offsets the spring pressure, and the boost pressure on the face helps open it up.

But if you encounter a backfire, which is positive pressure, it will actually close the BOV back up, but it is the actual backfire, happening below the throttle plates that bends them, a backfire could be well over 100 psi, which is why they bend.

Richard
 
Ah, Thankyou that was most informative. Nice to know I was running around with a part understanding.

Now back to your regular thread.
 
I'm going to pull her apart tonight. If they are bent, looks like my best bet is to get the whole throttle body assembly off of ebay for a few hundred bucks...

I've run this bike for 5 years now and over 100 pulls on the dyno, never had an issue like this before.
 
so I took her apart today, and good call, one of the blades were bent. Pulled it out and straightened is as best I could. Put it back together and she ran. Did not rev to the moon, but it did run like crap back firing etc.

Any thoughts? Should I replace all of the vanes or just get a second hand throttle body?
 
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