2021 FC450 RS running ratty off the bottom

kicker
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kicker
Hey guys, my bike started running pretty rough off the bottom/after starting at about 35 hours. Initially it would stall very easily at low RPM. It seems to clear up mostly after revving it out and riding it, but it's always there after starting and I can tell it's not running perfect. I've checked the usual suspects, fuel filter (not in tank), always fresh gas, always fresh air filter. Replacing the spark plug seemed to help somewhat so I think the real problem may have fouled it.

The only suspects I can think of is the no-toil I use on the air filter was sitting for a while once and I believe the bike stalled soon after starting it. I've seen it break down if it sits so maybe it got sucked in to the injector? But it's not consistent over the RPM range... I had also removed the connectivity unity shortly before the issue started, though reconnecting it doesn't clear up the issue.

Any help is appreciated! Cheers!
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Bruce372
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Bruce372 2/22/2022 11:00pm
2/22/2022 11:00pm
Maybe just turn the idle up a fraction?
Factor E
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Factor E 2/22/2022 11:07pm
2/22/2022 11:07pm Edited Date/Time 2/22/2022 11:08pm
Does it happen only after it is warmed up?
Idle should be 1800-1900 rpm
kicker
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kicker 2/23/2022 8:06am
2/23/2022 8:06am
Factor E wrote:
Does it happen only after it is warmed up?
Idle should be 1800-1900 rpm
It happens as I open up the throttle off idle. Idle alone sounds fine. Both cold and warm after start. After revving it out it clears up somewhat
mx317
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mx317 2/23/2022 8:44am
2/23/2022 8:44am
Hard to start?

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kicker
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kicker 2/23/2022 10:06am
2/23/2022 10:06am
mx317 wrote:
Hard to start?
No. It was flaming out and stalling easily when it first started happening and would be sometimes hard to start then, but since replacing the spark plug that mostly went away. The rough running stayed.
mx317
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mx317 2/23/2022 11:33am
2/23/2022 11:33am
mx317 wrote:
Hard to start?
kicker wrote:
No. It was flaming out and stalling easily when it first started happening and would be sometimes hard to start then, but since replacing the spark...
No. It was flaming out and stalling easily when it first started happening and would be sometimes hard to start then, but since replacing the spark plug that mostly went away. The rough running stayed.
Mine was doing that and the in-tank filter was cracked causing it to lose pressure. A lot of fuel pumps have been misdiagnosed as being bad because they have the same low pressure symptoms. Easy check is to look in the tank when it's running and see if the fuel is bubbling or appears to be boiling. Gas coming out of the cracked filter will make it do this.
mx317
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mx317 2/23/2022 11:34am
2/23/2022 11:34am
It's a quick and free check.
kicker
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kicker 2/23/2022 12:01pm
2/23/2022 12:01pm
mx317 wrote:
It's a quick and free check.
Thanks I’ll try that!
kicker
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kicker 2/26/2022 4:30pm
2/26/2022 4:30pm
So I replaced the filter in the fuel tank and initially I thought it fixed it, but after putting around on it in the street it seemed worse until it warmed up. I suppose the next culprit the whole fuel pump? I may try to take it out tomorrow to see how consistent it is.
Digger29
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Digger29 2/27/2022 8:21am
2/27/2022 8:21am
I'm pretty positive that if you adjusted the TPS's voltage that it would clean up those issues. They come pretty lean which makes them hard starting and not clean running right off of idle and definitely causes decel popping when chopping the throttle coming into a turn.
kicker
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kicker 2/27/2022 9:13am
2/27/2022 9:13am
Hmm it ran fine when I first bought it. It only showed up after I put about 20 hours on it
Grovesy98
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Grovesy98 2/27/2022 12:06pm
2/27/2022 12:06pm
I had some issues with my 17.5 KTM 450 FE recently. Rough running, low power, bogging, and decel popping. Had it on a dyno and it was running only 31bhp and lean right through the rev range! Turns out the fuel pump was toast and also had sand particles in it. I don't ever remember dropping any sand in, but could have been the previous owner. Anyway, new fuel pump and a few runs on the dyno with some tweaks to the mapping to optimize it has completely transformed the bike, it rips! Mine had done 86hrs when it let go
kicker
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kicker 2/27/2022 1:14pm
2/27/2022 1:14pm
So I have it out today and it turns out replacing the fuel filter in the tank did fix it. I guess the ecu just needed to adapt to the richer mix or something? The bike is back to ripping again. Thanks to @mx317 for the initial suggestion!
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