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I've been to every forum out there where someone has asked this same question (or something similar) years ago regarding their 400 stalling when decelerating/breaking and the original poster never came back to say what ultimately fixed the issue. So here we go, I'll be descriptive with the issue with an example included and then I'll provide things I've already tried.

Issue
I just purchased a KFX 400, it starts perfect and it idles perfect both cold and warm. Here's an example of when it stalls: I'm riding around my yard at a decent speed, I go to stop by: letting go of the throttle > holding in the clutch and using my front and back breaks (mostly the front) I can hear the engine slowing down like normal except it doesn't stop declining, it just gets weaker and weaker and then dies. Now, at THAT point of stalling it is now harder to crank then any other time, I even have to put the choke back on sometimes for it to crank; but once it does finally crank again we're back in business. Note: If I purposely turn it off myself I can instantly crank it right back up so I know it's not an overheating issue. It's only hard to crank after it unwelcomely turns off.

9 times out of 10, the stalling happens when I medium/semi-hard break, like if I'm going a little fast and then I have to come to a stop.(I'm not death gripping the front lever, to me it seems like a normal break, maybe even a tad harder but it doesn't happen if I'm going slow and then I break.) Does the front break have anything to do with the air flow in the carb? surely not right?

Side issue that may be related
No one holds down the throttle the entire time their riding, you got to let off sometimes maybe before a turn right? Well, randomly after letting off the throttle and pressing it again while I'm riding it won't do anything for a moment, it feels like a heart skipping a beat, like it just stutters for a moment and will just start going again. This is a 3/4 of a second occurrence but could mean the world under certain circumstances.

What I've done so far in attempt to fix

  • Turned up the idle
  • Cleaned all 3 jets on the carb. (used wire brush to clear the holes)
    • Note: I did not clean anything else on the carb, only other thing I did was check the floater to ensure movement and doesn't stick. I also want to mention that the carb looked surprisingly clean when I opened it up, looked like someone cleaned it not that long ago.
  • Took the gas tank off and deep cleaned it (Put pennies in it and shook it around in there for a while > drained it) so obviously there's fresh gas in there now, I even put a little sea foam in it to help clean the rest of the carb.
  • Remove/cleaned the petcock with carb cleaner spray.
  • Replaced the hose line and fuel filter connecting the tank to the carb, also replaced the overflow hose to the carb.
  • I'm not accidentally riding with the choke on.
  • On the petcock, I tried all 3 positions (Res/Pri/on) same thing happens on all 3.
  • Changed the spark plug
  • Changed the air filter
*The only thing I can think of that I didn't do was clean the entire carb, but I'm only going to put the time into that if someone thinks that's my next step.



Any help would be very much appreciated!!
 

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I've been to every forum out there where someone has asked this same question (or something similar) years ago regarding their 400 stalling when decelerating/breaking and the original poster never came back to say what ultimately fixed the issue. So here we go, I'll be descriptive with the issue with an example included and then I'll provide things I've already tried.

Issue
I just purchased a KFX 400, it starts perfect and it idles perfect both cold and warm. Here's an example of when it stalls: I'm riding around my yard at a decent speed, I go to stop by: letting go of the throttle > holding in the clutch and using my front and back breaks (mostly the front) I can hear the engine slowing down like normal except it doesn't stop declining, it just gets weaker and weaker and then dies. Now, at THAT point of stalling it is now harder to crank then any other time, I even have to put the choke back on sometimes for it to crank; but once it does finally crank again we're back in business. Note: If I purposely turn it off myself I can instantly crank it right back up so I know it's not an overheating issue. It's only hard to crank after it unwelcomely turns off.

9 times out of 10, the stalling happens when I medium/semi-hard break, like if I'm going a little fast and then I have to come to a stop.(I'm not death gripping the front lever, to me it seems like a normal break, maybe even a tad harder but it doesn't happen if I'm going slow and then I break.) Does the front break have anything to do with the air flow in the carb? surely not right?

Side issue that may be related
No one holds down the throttle the entire time their riding, you got to let off sometimes maybe before a turn right? Well, randomly after letting off the throttle and pressing it again while I'm riding it won't do anything for a moment, it feels like a heart skipping a beat, like it just stutters for a moment and will just start going again. This is a 3/4 of a second occurrence but could mean the world under certain circumstances.

What I've done so far in attempt to fix

  • Turned up the idle
  • Cleaned all 3 jets on the carb. (used wire brush to clear the holes)
    • Note: I did not clean anything else on the carb, only other thing I did was check the floater to ensure movement and doesn't stick. I also want to mention that the carb looked surprisingly clean when I opened it up, looked like someone cleaned it not that long ago.
  • Took the gas tank off and deep cleaned it (Put pennies in it and shook it around in there for a while > drained it) so obviously there's fresh gas in there now, I even put a little sea foam in it to help clean the rest of the carb.
  • Remove/cleaned the petcock with carb cleaner spray.
  • Replaced the hose line and fuel filter connecting the tank to the carb, also replaced the overflow hose to the carb.
  • I'm not accidentally riding with the choke on.
  • On the petcock, I tried all 3 positions (Res/Pri/on) same thing happens on all 3.
  • Changed the spark plug
  • Changed the air filter
*The only thing I can think of that I didn't do was clean the entire carb, but I'm only going to put the time into that if someone thinks that's my next step.



Any help would be very much appreciated!!
I haven't figured out either I'm having the same problems with my 03 Kawasaki 400 only has about a hundred hours on it I miss dying out when I I down rev and come to a stop
 
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