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Two bikes same problem, stalling at idle

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Hey guys,

 

I bought a 2017 KTM 350EXC-F a few months back and the bike has been running great. I've got about 65hrs on her now. At around 10hrs I installed an FMF 4.1 slip on and adjust the tps. No problems since then.

The bike just started stalling at idle. It will idle, hesitate a few times, then die. It starts bike up without issue then the same thing happens again. 

 

So so far I've:

Changed the oil 

Changed the oil filter

Changed the inline fuel filter

Dumped the fuel and replaced

Changed the spark plug

Re adjusted idle and TPS

 

None of that made a difference. My brother owns a 2016 KTM 250SXF. I decided to swap some of his parts onto my bike to see if I could narrow down the issue. I swapped the fuel tank, coil, and the ECU. None of these swaps made a difference at all. The weird thing is, is that his bike now exhibits the exact same issue. 

Hoping you guys may be able to point me in the right direction. I've included YouTube videos showing what is happening.

 

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It's certainly possible. Hell of a coincidence that my brothers bike would start acting up after switching the parts around though. We did not get gas from the same station or within the same week. 

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Have you tried an ECU reset , by disconnecting the positive side of the battery for a short period, then do the no throttle initialization procedure.

 

sounds like it gradually leans itself out till it dies, was that video off a cold start?

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Yes, I have tried resetting the ECU. The videos are cold starts on both bikes. However, it does the same thing when they are hot. When not at idle they both run great. 

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5 hours ago, m_renken said:

Could you have a dirty injector?

 

 

I would bet on that plus dirty tank fuel filter:

 

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Alright, so I cleaned the fuel injector but it didn't change anything. Unfortunately none of the local shops had in tank fuel filters. I did however pull mine out and hose it down with carb cleaner and blow it out with compressed air. It had black fuel in it just like the video posted above. That didn't help either. I have ordered a new in tank filter and will install it when it gets here. Not sure this issue is fuel related though. I double checked the tps, and it's still at .61v. 

 

Any other ideas? Probably going to take it to the dealer tomorrow. It's still under warranty, just prefer to work on my own stuff. Maybe they can do a computer diagnosis?

Edited by Knichols97045

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Hey Knichols97045,

Did you found out what caused the stalling at idle on your Ktm350? I’ve put my original muffler back on and now my bike is doing the exact same thing as you described.

Cheers

Des

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Yes, I did find out what the issue is. Both of our bikes had small tears in our spark plug boot. Spark was grounding out through the boot to the head. We replaced the spark plug boots on both of our bikes and the issue is completely resolved. To pull the plug boots on these bikes it requires you to bend them sideways to clear the frame. I’ve been applying a light amount of grease when I put them in now. 

 

Hope this helps. 

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16 hours ago, Knichols97045 said:

Yes, I did find out what the issue is. Both of our bikes had small tears in our spark plug boot. Spark was grounding out through the boot to the head. We replaced the spark plug boots on both of our bikes and the issue is completely resolved. To pull the plug boots on these bikes it requires you to bend them sideways to clear the frame. I’ve been applying a light amount of grease when I put them in now. 

 

Hope this helps. 

The tears were visible on the outside of the boot?

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20 hours ago, Knichols97045 said:

Yes, I did find out what the issue is. Both of our bikes had small tears in our spark plug boot. Spark was grounding out through the boot to the head. We replaced the spark plug boots on both of our bikes and the issue is completely resolved. To pull the plug boots on these bikes it requires you to bend them sideways to clear the frame. I’ve been applying a light amount of grease when I put them in now. 

 

Hope this helps. 

How did you diagnose this? I'm mainly looking to learn how to spot this on my own bike in the future.

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5 hours ago, Horgh said:

How did you diagnose this? I'm mainly looking to learn how to spot this on my own bike in the future.

turn off the lights, look for any sparks.

2 bikes torn Boot, same mechanic?

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9 hours ago, OX MAN said:

The tears were visible on the outside of the boot?

Yes, but when bent just slightly they become much more visible. 

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13 minutes ago, Spud786 said:

turn off the lights, look for any sparks.

2 bikes torn Boot, same mechanic?

You can’t see any spark on these bikes with the boot is inserted in the engine. 

Yes, I worked on both bikes. Like I said though, in order to pull the boots on these bikes(250 and 350, I don’t think the 450 and 500 are the same) you have to bend them at a pretty severe angle to clear the frame and pull them out. When you do this it’s highly likely that you can tear the boot. Coat the boot in a light amount of grease to make it easier to pull the next time. 

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6 hours ago, Horgh said:

How did you diagnose this? I'm mainly looking to learn how to spot this on my own bike in the future.

Pure luck... My brother randomly noticed a the tear in his boot while he had his bike apart trying to figure out what was causing the problem. His tear was larger than mine and got to the point that his bike stopped starting completely. 

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