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Discussion Starter · #1 ·
Does anyone know where I can get replacements or a different style joint for the plastic ball joint cups that connect the throttle bodies? At 13k miles, mine has too much play in it. If i adjust it so both throttle bodies open at the same time, there is enough play that I can push the rear throttle plate open slightly. This becomes a problem when the bike has been running for a while as it will suck that plate open at idle and my idle will hang at 1700 to 1800 rpm. If I adjust the link back to stock, the linkage will make sure both throttle bodies are fully closed at idle and neither will be sucked open due to play. However, my horizontal cylinder will start to rev up earlier at the crack of the throttle due to the linkage play. This can cause it to run a little rough at that initial crack.

I was wondering if there were any alternatives. I forgot what the throttle cam looked like when i had it out. Is the ball molded to it or screwed in? Maybe a metal heim joint would last a bit longer.
 

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Good question. I've not seen a problem with that assembly before. Maybe you just have too much play in the return throttle cable?
 

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These are definitely an issue, and I have discussed this here before. Don't ask me which thread, as it was years ago!

The play I had remarked on was more with regard to uneven opening, where the rear cylinder developed a slight delay due to the wear.

My suggestion was to check and adjust the linkage for even opening (a light behind the butterfly can be helpful) when the airbox was removed during valve adjustment.

But I had not noticed this play causing the idle to rise, even though mine has covered almost 80,000 kms now.

It may be worth checking that they are opening evenly, and that your closing throttle cable is holding them closed. But the springs against them should prevent this rise in idle.

You may have another issue, such as an air leak or a TPS problem.
 

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Discussion Starter · #4 ·
Good question. I've not seen a problem with that assembly before. Maybe you just have too much play in the return throttle cable?
definitely not. airbox/throttle body assembly was tested off the bike. by simply pressing on the butterflies.
 

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Got ya, well sometimes they crack where the shaft which connects the two throttle bodies goes together. Maybe you should make sure there isn't any play in that as well.
 

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Discussion Starter · #6 ·
These are definitely an issue, and I have discussed this here before. Don't ask me which thread, as it was years ago!

The play I had remarked on was more with regard to uneven opening, where the rear cylinder developed a slight delay due to the wear.

My suggestion was to check and adjust the linkage for even opening (a light behind the butterfly can be helpful) when the airbox was removed during valve adjustment.

But I had not noticed this play causing the idle to rise, even though mine has covered almost 80,000 kms now.

It may be worth checking that they are opening evenly, and that your closing throttle cable is holding them closed. But the springs against them should prevent this rise in idle.

You may have another issue, such as an air leak or a TPS problem.
This is the issue i am seeing. No leaks or tps problem.
I had it set so that the slack was removed and both throttle butterflies opened at the same time instead of a slight lag in the vertical butterfly due to slack. This resulted in great and smooth throttle tip in. However, with both throttle blades closed, I can push the vertical butterfly open slightly without the horizontal moving. This is caused by the slack in the ball joints. When i had the throttle adjusted so that both open at the same time, the vertical cylinder butterfly would get sucked open slightly due to the velocity and suction of the air.

This was a common issue on larger single blade throttle bodies used on 2003 Mustang Cobras. The throttle blade would often get sucked open at idle due to the vacuum behind the butterfly. Now in the case of my bike, its easier to suck open because of the play in the throttle linkage.

To prove this, I adjusted the linkage back so that when both butterflies are closed, i cannot open the vertical butterfly without the horizontal moving. This means when i crack the throttle, the horizontal butterfly will open first followed by the vertical as the slack is taken up. I may pick up a used throttle body assembly and look into replacing the ball joints with something like a heim joint.
I just have to see how the stock ball joints are attached. I'm guessing they need to be drilled out.
 

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Discussion Starter · #7 ·
I've decided the first thing I'll try is an old trick i learned with R/C helicopters. Heating the plastic cup while its off the ball just a bit. this slightly reshapes and shrinks it for a tighter fit. Fingers crossed because i loved the throttle response when it was synced properly.
 

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Discussion Starter · #8 · (Edited)
so just a reference in case anyone else is having the same issue. I pulled my airbox out and pulled the linkage off the ball ends of the throttle bodies. I used a heat gun to melt the plastic ball ends and pressed the ends a little at a time to make sure I don't overdo it, while making sure it pops onto the ball without easily pulling out. the open end of the links are not pretty after the reformation, but it works perfectly and you can't see it once installed. No slop in the ball ends for now and they still move freely. Now the throttle bodies open and close at the same time without worrying about the rear hanging open from the suction of air taking up the slack in the throttle linkage. If you plan on doing this, remember to heat it up and press the ends a little at a time while test fitting.

That said, I am getting depressingly good at removing my airbox, etc. The entire job including removing body panels, fuel tank, throttle, etc took about 1.5 hours. Throttle response at small openings is very sharp again. Love it.
 
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