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Missing/popping/sneezing at idle


Tinus89
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After replacing the gearbox, I have this exact issue:  Missing/popping/sneezing at idle and at minor throttle (until ~3000rpm when running very light loads). When I VERY slowly increase the throttle a little, I can usually make the pop happen.

 

Must know: When installing the gearbox, I very briefly made a short circuit between the battery positive and the frame. Could this be related?

 

Done so far: cleaned TB's, set TPS at 153mV (showing 540mV at idle), balanced at idle, rode her, minor improvement.

Then I set the valves to 0.22/0.18mm. This did give improvement, but did not take the issue away.

 

What else can I do?

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I would check for a vacuum leak.

 

Throttle body rubbers are in good nick and properly installed. No cracks etc. Screws for the throttle balancing are tight with an aluminium washer underneath.

Where else could she draw air?

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Looks like you already checked for a vacuum leak.  :) Sounds lean, for whatever reason, though. 

Of course, that means it's probably electrical.  :ninja:  Do you have GuzziDiag?

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[edit: This OP asked  that these posts be moved to create a new thread for the issues Tunus69 is having.  A few of the new posts from the old thread did not make the trip. My apologies for that. ]

 

> As to developing a running issue after gearbox removal, it occurs to me that the main electrical ground to the back of the gearcase on the right might not be tight or is otherwise disturbed.

 

> I expect the airbox was also removed, so the air temperature sensor connection should be checked. 

 

> Since the tank was also likely off, make sure the petcock is now turned fully on.

 

> When the tank is replaced, the clamp for the return line to the regulator on the right side has been known to foul the TPS.

 

Likely something simple! :luigi:

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Check for exhaust leaks too. They can cause symptoms like this, especially at idle.

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It does sound lean.  If you've ruled out vacuum leaks it could be your CO trim is set way lean.  Do you know what your TPS setting was before you touched it?  Do you know what your CO trim is set at?  Are your idle air bypass screws all the way in or out?

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It does sound lean.  If you've ruled out vacuum leaks it could be your CO trim is set way lean.  Do you know what your TPS setting was before you touched it?  Do you know what your CO trim is set at?  Are your idle air bypass screws all the way in or out?

+1 ^

When i’ve tuned/tinkered with my v11 i’ve found the air screws play a significant part in getting her running well.

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Thanks for moving the topics and all the replies!

 

> As to developing a running issue after gearbox removal, it occurs to me that the main electrical ground to the back of the gearcase on the right might not be tight or is otherwise disturbed.

 

> I expect the airbox was also removed, so the air temperature sensor connection should be checked. 

 

> Since the tank was also likely off, make sure the petcock is now turned fully on.

 

> When the tank is replaced, the clamp for the return line to the regulator on the right side has been known to foul the TPS.

 

Electrical ground is tight, but I will measure it to ensure electrical connection is OK.

Airbox was not removed, as I don't have one (K&N filters). Air temp sensor is relocated underneath the seat cowl and gives the right temp in GuzziDiag

Tank has not been off, petcock is open. Nothing is making contact with the TPS:)

 

 

Check for exhaust leaks too. They can cause symptoms like this, especially at idle.

 

Good point, as they have been off for the gearbox install!

 

It does sound lean.  If you've ruled out vacuum leaks it could be your CO trim is set way lean.  Do you know what your TPS setting was before you touched it?  Do you know what your CO trim is set at?  Are your idle air bypass screws all the way in or out?

 

CO trim was set to zero, but changing it to either +10 or -10 did not affect the idle running. I agree it sounds lean. When I was balancing the throttle bodies, I heated up the right exhaust bend to dark orange...

My air bypass screws are about 1 and 2.25 turns out (right hand side more -> which is the side that glowed the exhaust bend.

I think you may have an excellent point here, I will turn them both a bit more in and adjust with the idle setting to get her running properly.

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First report:

 

Electrical connection of gearbox ground is good.

No leaks in the exhaust.

 

I fully closed both air bypass screws and then turned them out 1/4 turn. Balanced her by opening the left air bypass for about another 1/2-3/4 turn, balance was excellent then.

Rode her: pops on the right side are gone. Some still present on the left side, but much less annoying. After coming back I decided to close the left one 1/4 more, I'll have to ride her again to see what that did. But certainly big improvement and slowly getting there:).

 

Question: as the right one is stil 1/4th turn out, is there any reason why I would not want to close that one entirely and use only the left idle screw to balance her?

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