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Discussion Starter · #1 ·
Brief rundown - has only started since I switched to the Get ECU (taco moto maps). but upon switching back to factory ECU with fuel tuner its having the same issues Saturday was my third trip where I got to sit at the loading zone because of this issue.

Bike Setup:

2017 ktm 500
desmogged
reeds removed, with intake port
fmf 4.1
get ecu from taco moto
everything else is stock

Basically what happens is the bike fires up and runs normal, 20 - 30 minutes in to the ride it goes from normal running to running like a carbureted bike with the choke on, it barely idles in map one, and wont even run at all in map two. When running in map 1 trying to get back to camp, it endlessly pops, and has absolutely no power and will completely bog if i go past half throttle.

What I have done so far to try and remedy

  • checked all grounds/electronics/fuses
  • new fuel pump
  • new inner fuel filter
  • new external fuel filter
  • Cleaned the fuel injector
  • Replaced ground strap, and ran an additional ground to the frame
  • clean fuel tank and fuel and all new hoses
  • checked and shimmed valves to spec
  • verified fuel pressure while running (consistent 50-52 PSI)
  • verified no leaks or cracks in intake boots along with verified they are sealing correct
  • even went as far as putting on a brand new no toil air filter lol ( although i didn't think this had anything to do with it)
  • Get ECU is on its way to taco moto now for testing but I am not positive that's actually the culprit

The issue is still happening but not every time, it's intermittent. I had a successful weekend ride where I rode for 6 plus hours with no issues. So I am at a loss. I haven't checked the TPS, I could see a TPS issue being it if the issue was consistent, but the fact that it runs sometimes and not the others makes me think something else. It still seems to my brain to be fuel delivery, but I have checked and checked and checked everything and its all running as it should fuel wise.



I am open to suggestions of any type, or anything I can look into. I will even buy lunch to whoever can help me figure this out XD

Thank you guys for the help
 

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No mention of spark plug readings. What color ye got on the firing end? Hope you replaced spark plug resistor cap before you went bonkers on this thing. Sounds like you have checked all possibilities here. I would tend to agree with your diagnosis condemning the ECU. They can wig out and send fuel and ignition curves all over the place. Seems likely this is your culprit until you revert to original and have same complaint. I would hope to try stock settings or stock unmolested ECU for baseline tests if possible. This would eliminate suspicion. I would suspect stator breakdown as another possibility if it cut off or refused to rev past 4000rpm. Hopefully your taco dude has some ideas? Maybe they have tech assistance crew there? Worth a call I reckon. Report back with your progress. Good luck
 

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Discussion Starter · #3 ·
No mention of spark plug readings. What color ye got on the firing end? Hope you replaced spark plug resistor cap before you went bonkers on this thing. Sounds like you have checked all possibilities here. I would tend to agree with your diagnosis condemning the ECU. They can wig out and send fuel and ignition curves all over the place. Seems likely this is your culprit until you revert to original and have same complaint. I would hope to try stock settings or stock unmolested ECU for baseline tests if possible. This would eliminate suspicion. I would suspect stator breakdown as another possibility if it cut off or refused to rev past 4000rpm. Hopefully your taco dude has some ideas? Maybe they have tech assistance crew there? Worth a call I reckon. Report back with your progress. Good luck
Thanks for the reply. I do have a spare spark plug and did try that. forgot to list it. The original spark plug I pulled out looked as normal as a used sparkplug could to me, slighting warn but no heavy residue of any type and not burnt. I will try just stock ECU, with no tuner and see how it does however the stock map is so lean I am not sure it would run even if it was working normal. I am sending the ECU to Taco today, he is going to test it in his shop and if its defective or bad maps or whatever he will get it fixed up, but I am still not positive thats the issue. Stock ECU then Stator next. Thanks for the help!
 

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I was suggesting you replace the spark plug resistor cap. They sometimes break down inside and cause stumble or compete ignition breakdown in mid range
 

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Discussion Starter · #5 ·
I was suggesting you replace the spark plug resistor cap. They sometimes break down inside and cause stumble or compete ignition breakdown in mid range
ohhh, gotcha. I have not done that yet. I did cut a quarter inch off the end of the wire so its a fresh connection, but I will order a cap too. Does seem like moisture could get in and live in there.
 

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The carbon insert will sometimes breakdown inside the cap. The tension spring that holds insert tightly loses tension with heat from the big 4 strokes. Once the insert loosens and rattles around it arcs inside and dissipates spark energy needed to fire spark plug under load. Bastard will start and idle but sputter and spit like a bag of a$$holes under load
 

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Discussion Starter · #7 ·
The carbon insert will sometimes breakdown inside the cap. The tension spring that holds insert tightly loses tension with heat from the big 4 strokes. Once the insert loosens and rattles around it arcs inside and dissipates spark energy needed to fire spark plug under load. Bastard will start and idle but sputter and spit like a bag of a$$holes under load
thanks! tested that and confirmed fitment and voltage. but also ordered a new one just to be safe. its on its way. I did find a cable connected to the hardness that was corroded but I am confused as to what it even is. doesnt seem to be related to de smog, but its a looped dongle at the end of a cable, 5 wires that just go back into them self via connecto. any ideas? It was in the airbox but looks like it probably lives under the seat and was just pushed down there for space
 

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Do you have a picture available? Dirty connection on a sensor or dongle can cause high resistance and possible sensor/dongle voltage error. Gotta check everything until it's fixed. Keep at it. Check back with you progress or frustration.
 

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Discussion Starter · #9 ·
Do you have a picture available? Dirty connection on a sensor or dongle can cause high resistance and possible sensor/dongle voltage error. Gotta check everything until it's fixed. Keep at it. Check back with you progress or frustration.
Sorry for not replying. I am still plagued by this but I think I may have made some progress. This issue has ruined a few more rides lol, but im still trying.
I replaced the fuel pump again with taco motos new pump, new filters, new hoses, verified all wiring on the loom. tested my coil and my stator and it tested within spec per the repair manual. bought the motion pro injector cleaner online and cleaned it the "best" way possible. still same issue. Today while scouring hundreds of forum posts all over the web I saw someone describing a similar issue, they claimed it was MAP sensor related and that unplugging the map sensor would make it run perfect. so I wen out tried to start it, and it wouldn't start. I tried 10 or so times. Then I unplugged the map sensor and it fired right up and ran perfectly.

so just to make sure I am not crazy, this seems to be my culprit? Is it worth the $180 for a new one, or do the passage ways to the map sensor just need to be cleaned? Any advice would be helpful.
If anyone knows of a correct way to test the map sensors functionality please let me know, I couldnt find anything on Keihins site or Ktms manuals.
 
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