First of all, my '09 KLX250s runs perfectly 99.5% of the time. Dynojet kit, clean carb, exhaust & airbox mod... idles fine/smooth, accelerates great, cold start/choke is perfect... super happy with it.

BUT the other 0.5% no so much. Sometimes when cruising along and then closing the throttle from 55-65ish mph, and braking/coasting for a turn, it will just die/stall after a second or two into coasting. Only in 6th gear, only when cruising at 60ish for a minute or longer, and then rapidly closing the throttle and beginning to brake. It starts right back up and runs fine ( I usually wait to make the turn first). No other issues... none. Only does it sometimes?? Thoughts? I have turned my idle up to about 1800 rpm (I like a high idle for trails/less stalling - no issues with that).

I've tried running in gears 1-5 up to 8k rpms for 30 seconds or so and closing the throttle/braking ,and it won't do it then. Only after cruising at 60/6th and quickly slowing to turn.

I do have an inline "L" shaped (clear plastic) fuel filter/strainer between the petcock and carb. I do notice sometimes when I turn the fuel on I see bubbles in the filter as fuel enters - seems normal. And this evening after a long ride I turned off the fuel, took off my gear, and when I looked at the filter it didn't look like much fuel was in it so I turned the fuel/petcock back on. It didn't look to me like the fuel was quick to fill/flow into the filter and to the carb (mostly full tank). I haven't taken a petcock apart in a long time. Is there anything in our petcocks than can break/damage to keep fuel from flowing as freely as it should?

All I can figure in the stalling issue is maybe inertia slowing/starving fuel flow when decelerating quickly? Any and all thought and comments are appreciated!

 

No ones else has experienced this?

 

I would think that if there is a restriction, it would be most noticeable under prolonged heavy load. That's going to require the highest flow rate.
Sounds like a 'flame-out' where it goes lean under that condition-I'd double check the float level and adjust the idle mixture.

 

Thanks... idle mixture double checked, float level is gtg/OEM spec. I have heard of others with this issue bumping the idle rpm up, and have done that. I'll take the petcock apart and see what's going on in there. Thanks

 

Sounds like a partially clogged pilot jet to me.

 

Thanks Bob.... may be. But when i installed the jet kit I cleaned the tank, took out/cleaned the intank strainer/filters, added a filter between petcock and carb, and carb was like new clean. Doesn't mean something didn't make it in there somehow.

FWIW, I called Dynojet and they gave me their basic troubleshooting guide. But one thing they mentioned was moving the needle clip one notch richer on the slide....? Thoughts?

​​​​​​But the main issue/mystery to me is that it runs like a new bike, real strong, in every other way... I can't get it to stutter/sputter redlining it in any gear while riding...?

Thanks for the comments

 

Update:

So petcock checks out/functions properly. Bike seems to run good. BUT I found that the stall is after a closed throttle/coast/brake from the near WOT position itself... not just 6th gear. I got it to do it in 4th and 5th after a short distance at/near WOT, then rapid deceleration/closed throttle.

So the next question is, maybe too lean of the midrange or WOT carb fuel circuit ? It accelerates great when riding hard but I usually rev out in mid range before hitting WOT. This is my first 250 in a long time, but it feels like it's pulling pretty hard for what it is (have a 44T rear/14 front). So, lower the needle clip one notch... or increase main jet one notch? Which would you try first? I guess needle is easier.... Thanks

 

So I've done some reading and a few guys say stalling when braking could be a rich condition...? Pulling it apart again tomorrow. Would you set float on the higher side or lower in general for this issue. I'll guess we'll see where it is first. Thanks

 

I used to have my SR500 do that occasionally. I think it may have happened on the KLX650, but I don't remember. I think it might have been fuel sloshing forward in the float bowl or the like, causing a rich condition. Another situation too, would be pulling i the clutch and shutting the throttle quickly, possibly causing a back fire stalling the engine. The SR did that occasionally, but that was usually when starting out.

 

Roger... here's exactly what happens when it happens. Riding down the road in 6th at 65ish mph while still accelerating at/near wot, I intentionally wait until the last minute to clutch/brake for a turn, when I do I look down at the tach and see it drop off normally, but it very smoothly, and kind of slowly, drops right past my set rpm on down to 0 and stalls. I couldn't even tell it happened the first few times. I immediately hit the start button while rolling through the turn and it fires right back up with no other issues.

It 'feels' more like a sloshing, or vacuum, stall more than something much more abrupt. It seems like something is either robbing it of fuel at that point, or flooding it with fuel. But it seems that if it were being flooded with fuel that it shouldn't/wouldn't fire right back up so fast in the turn (it right after the turn)...??

I do have the front/top vac port on the carb (that used to go to the PAIR valve) capped off. Does the carb need to be vented there , or was that just to activate the pair valve? It just runs so good otherwise, it's hard to imagine what would be doing it. Thanks for the help guys.