2021 KTM 85 Issue

Rnewton632
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Rnewton632
Just a little back story, we had a 2020 KTM 85 with 100 hours on it that has been bulletproof. My son races the GNCC series, so the bike sees a lot of different environments. Bought a new 2021, set it up the same as 2020, and round two was his first race on it. The race was in Florida and it was pretty wet with some deep sand pits and standing water. On the last lap, about a mile before the finish, the bike died. My son says he was hammering down a straight, and it sounded like it all of a sudden fouled a plug. With help from a nice spectator, they finally got the bike started about three minutes later, and it ran perfect to the finish line. He was in 2nd place, and fell to 5th while trying to get his bike going. Heartbreaker! I couldn't find anything obvious, so I came to the conclusion that one of the carb vents got plugged. I routed one of the vent lines to the airbox and took him riding again on the following Tuesday. He rode about an hour and fifteen minutes and the bike ran and sounded perfect. At round three in Georgia last weekend, it did the same thing, this time on lap 2. It didn't take near as long to start this time. He said approx 1-1.5 minutes. Keep in mind this is coming from a 12 yr old, but he says it gives no warning, just dies, and doesn't sound like it's firing when he tries to restart it. Fell back to 12th place. Once again, bike ran perfect after restarting and he worked his way back to 5th. I currently have checked all electrical connections, and they were all firmly plugged in. I have the bottom of carb off, and float seems to be working correctly. Bike has 5.7 hours on it. Any advice on what to check?
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Paw Paw 271
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Paw Paw 271 3/17/2021 12:57pm
3/17/2021 12:57pm
Sounds like you may have an ignition coil breaking down when heated. You can do an ohms test on both the primary and secondary sides of the ignition coil to make sure the numbers look correct. If the resistance is too low on the primary side the coil will breakdown when heated and you will loose spark until it cools down.
The other thing is the stator will do the same thing.
What does the spark plug look like? Color of the tip?

Paw Paw
Rnewton632
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Rnewton632 3/17/2021 1:07pm
3/17/2021 1:07pm
Paw Paw 271 wrote:
Sounds like you may have an ignition coil breaking down when heated. You can do an ohms test on both the primary and secondary sides of...
Sounds like you may have an ignition coil breaking down when heated. You can do an ohms test on both the primary and secondary sides of the ignition coil to make sure the numbers look correct. If the resistance is too low on the primary side the coil will breakdown when heated and you will loose spark until it cools down.
The other thing is the stator will do the same thing.
What does the spark plug look like? Color of the tip?

Paw Paw
I didn’t check the plug after the 2nd time this happened, but after the first episode the plug looked great. I compared it to the plug in our other 85 and looked identical. I checked the stator and the ohm reading was within specs. I couldn’t get a good reading on the coil, but will be trying again tonight. A friend of mine, who is a much better mechanic than me, is coming by tonight to help. We will check the coil. Thank you for the reply.
Tracktor
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Tracktor 3/18/2021 10:22am
3/18/2021 10:22am
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after hours of testing & messing with bike I was revving it out and put rested my hand on it. Ran perfect, lifted hand started cutting out. Ended up zip tying plug into CDI until I could buy a new harness...I also hardwire the white (beginner" connector as we had it come loose and cause some odd running issues on one.......Also could be a grounding issue. Check grounds especially around coil & try disconnecting kill switch.........
Rnewton632
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Rnewton632 3/18/2021 11:13am
3/18/2021 11:13am
Tracktor wrote:
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after...
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after hours of testing & messing with bike I was revving it out and put rested my hand on it. Ran perfect, lifted hand started cutting out. Ended up zip tying plug into CDI until I could buy a new harness...I also hardwire the white (beginner" connector as we had it come loose and cause some odd running issues on one.......Also could be a grounding issue. Check grounds especially around coil & try disconnecting kill switch.........
Thank you, I will test the CDI plug tonight to see if I can get it to act up. As paw paw stated above, I am leaning towards the coil. I got called back work last night so didn't get a chance to do much testing. I'm going to have him ride it tomorrow evening and hopefully it will replicate the problem. I'll just pop the spark plug out to see if it's sparking when it dies so at least I'll know for sure it's electrical. I'm taking our other bike with us so I can start swapping parts to see if I can pinpoint the cause.

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Tracktor
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Tracktor 3/19/2021 1:46pm
3/19/2021 1:46pm
Tracktor wrote:
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after...
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after hours of testing & messing with bike I was revving it out and put rested my hand on it. Ran perfect, lifted hand started cutting out. Ended up zip tying plug into CDI until I could buy a new harness...I also hardwire the white (beginner" connector as we had it come loose and cause some odd running issues on one.......Also could be a grounding issue. Check grounds especially around coil & try disconnecting kill switch.........
Rnewton632 wrote:
Thank you, I will test the CDI plug tonight to see if I can get it to act up. As paw paw stated above, I am...
Thank you, I will test the CDI plug tonight to see if I can get it to act up. As paw paw stated above, I am leaning towards the coil. I got called back work last night so didn't get a chance to do much testing. I'm going to have him ride it tomorrow evening and hopefully it will replicate the problem. I'll just pop the spark plug out to see if it's sparking when it dies so at least I'll know for sure it's electrical. I'm taking our other bike with us so I can start swapping parts to see if I can pinpoint the cause.
IN all my years of running KTM 85's we never saw or heard of a bad coil. Not to say it isn't the issue just personal experience & Pawpaw definitely know his stuff. Let us know what you find.

Try posting in the mini forum on KTMTALK also there is good bike specific info there too....I take it you checked the main vent on the fuel cap?.....
Rnewton632
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Rnewton632 3/19/2021 6:17pm
3/19/2021 6:17pm
Tracktor wrote:
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after...
We have had issues with the wire harness plug where it goes into the CDI. The CDI one was very similar I only figured out after hours of testing & messing with bike I was revving it out and put rested my hand on it. Ran perfect, lifted hand started cutting out. Ended up zip tying plug into CDI until I could buy a new harness...I also hardwire the white (beginner" connector as we had it come loose and cause some odd running issues on one.......Also could be a grounding issue. Check grounds especially around coil & try disconnecting kill switch.........
Rnewton632 wrote:
Thank you, I will test the CDI plug tonight to see if I can get it to act up. As paw paw stated above, I am...
Thank you, I will test the CDI plug tonight to see if I can get it to act up. As paw paw stated above, I am leaning towards the coil. I got called back work last night so didn't get a chance to do much testing. I'm going to have him ride it tomorrow evening and hopefully it will replicate the problem. I'll just pop the spark plug out to see if it's sparking when it dies so at least I'll know for sure it's electrical. I'm taking our other bike with us so I can start swapping parts to see if I can pinpoint the cause.
Tracktor wrote:
IN all my years of running KTM 85's we never saw or heard of a bad coil. Not to say it isn't the issue just personal...
IN all my years of running KTM 85's we never saw or heard of a bad coil. Not to say it isn't the issue just personal experience & Pawpaw definitely know his stuff. Let us know what you find.

Try posting in the mini forum on KTMTALK also there is good bike specific info there too....I take it you checked the main vent on the fuel cap?.....
He rode for two solid hours this evening and of course it ran perfect. Beginning to think it may be carb related, just not sure what it could be. I’ve had a float stick open before, but never closed. I checked the fuel tank vent right after the first episode because I had that problem years ago on one of my bikes. I just hope I can get it to happen again so I can diagnose what’s going on. If it’s getting spark, I’ll know it’s carb or air related. If no spark, I can start swapping electrical components. He will be racing his other bike until I can figure this out. Very frustrating, I appreciate the help.
Hoseclamp
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Hoseclamp 3/25/2021 6:06am
3/25/2021 6:06am
I JUST dealt with a situation like this on my sons ktm 65. Skipping over the long story and all the details of shit we messed with first, we ended up finding a wire that went into the cdi box plug was ALMOST broken and wiggling around just from vibration it was making connection on and off. You could not see that the wire was a problem, it looked like it was in the plug just like all the other wires. When we pulled the cdi box out that extra movement "popped" the wire entirely free from the plug making the problem obvious. Electrical problems suck. Good luck. Let us know what you end up finding out.
Rnewton632
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Rnewton632 4/6/2021 11:35am
4/6/2021 11:35am
Update: He's put six total hours on the new bike since the last time it had the issue. I found a couple small pieces of debris in the carb. It looked like some excess silicone that was used on the gasket between the bowl and carb body. I cleaned the carb and just to eliminate a variable, I swapped carbs between the two bikes. So since the second episode, he's put 6 hours on new bike, and about the same on his practice bike with no issues.

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