Engine surging

jrevans

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You guys are motivating me to start diagnosing my FZ6. Last fall when I went to give it a ride and fill it with fuel and stabilizer for the winter, it developed a miss once it warmed up, and actually stalled on me. Sadly, I only rode about 150 miles last year (maybe less), and although I had fuel stabilizer in it, I may not have even gone though the tank of fuel. I had to keep revving the bike to keep it from stalling.

For all I know there could be a mouse nest in the air filter, as I didn't do any diagnosis yet, but it was odd that it started and ran fine until it warmed up. I filled it with Ethanol free gasoline and added some seafoam and took it for another ride, but it still acted up. I added stabilizer and put it away for the winter, but I plan to actually ride more this season, so I need to start diagnosing my problem, and this thread has been helpful.
 

trepetti

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Sadly, I have an update. The victory dance was premature.

In a nutshell, the problem does not pop up right away and so it is hard to really tell if it is fixed or not. In the weeks working on this I have discovered a loop that so far has been 100% in bringing the problem on.

Changes to date:
- New OEM coolant temp sensor
- Replaced TPS and Intake air pressure sensor
- Replaced entire throttle body and injectors (lower-mileage eBay unit)
- Replaced 4 COP coils with newer units
- Replaced spark plugs
- Compression test
- Throttle body sync

What next?
The last time I reassembled the under tank parts, I took GREAT care in the throttle body joints, to the airbox and to the engine. The result was the problem getting much better but not gone. The airbox joints are a suspect, so I want to reseal them.

I am considering Gorilla Spray Sealant. Has anyone ever resealed these joints? Let me know what you have used, or what you WOULD use if you did the job today.

Thanks....
 

TownsendsFJR1300

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Gary in NJ

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Tom,

Are you talking about the rubber isolators (what the Yamaha parts fich is calling Joint, Carb - pns 5SL-13586-01-00 (x2) and 5SL-13596-01-00 (x2) )? I would not try to seal those or find a cheap alternative. Through continuous heat cycles those items get hard and unyielding. If they do not easily deform and return to shape, then I would suggest replacement. This is something that should have identified itself during the propane survey, but given the downdraft nature of the intake system, it may have been missed.
 

trepetti

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Tom,

Are you talking about the rubber isolators (what the Yamaha parts fich is calling Joint, Carb - pns 5SL-13586-01-00 (x2) and 5SL-13596-01-00 (x2) )? I would not try to seal those or find a cheap alternative. Through continuous heat cycles those items get hard and unyielding. If they do not easily deform and return to shape, then I would suggest replacement. This is something that should have identified itself during the propane survey, but given the downdraft nature of the intake system, it may have been missed.
Not those Gary. The joints in the airbox that interface with the top of the throttle bodies.....
 

Gary in NJ

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They shouldn't require any sealant (unless they have failed). Since they are before the TB they should not impact the ability of the engine/ECU to set idle or lead to a lean surge. The issue with sealing them is that you risk the possibility of FOD. If you believe that a leak may lead to unbalanced induction, simply leave the airbox off for a test run.
 

trepetti

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They shouldn't require any sealant (unless they have failed). Since they are before the TB they should not impact the ability of the engine/ECU to set idle or lead to a lean surge. The issue with sealing them is that you risk the possibility of FOD. If you believe that a leak may lead to unbalanced induction, simply leave the airbox off for a test run.
Thanks Gary, I understand. The latest angle I am chasing is that the issue cropped up shortly after I had to rebuild the starter, which was the first time ever the TBs were removed.

As I mentioned above, when I last reinstalled the TBs, I took my time inserting the lower joints to make sure I did my best to avoid any vacuum leak. Afterwards the bike ran a LOT better, with a slight misfire in a much narrower RPM range. I got to thinking about what I might have done differently that had such a big influence on the problem.

I ordered some new lower joints, hope to have them early next week.

As for the airbox joints, there was some 'stuff' on the underside of the airbox where the joints go through. The stuff was brittle and flaking off, so I cleaned it off and initially used black RTV as a substitute. This was also done when the starter was rebuilt.

I agree that, since my problem is certainly related to high manifold vacuum, and these airbox joints being above the butterflies should not influence manifold vacuum. I just wanted to replace the 'stuff' originally there with something appropriate.

Oh, and add to my list above, I had also removed the ECU and inspected / cleaned the contacts......

Failure is not an option.......

A newer FZ6 MIGHT be an option :)
 
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