Stalling issue

6 replies to this topic
  • RiderX

Posted September 25, 2011 - 06:04 PM


So I've been fighting this problem since I bought this bike about 6 months ago and I'm running out of ideas. My bike stalls at idle at times and on uphill climbs (I have a Rekluse). It's really frustrating. I've tried every thing short of pulling the carb completely apart. I've replaced the jets, replaced the spark plug, I've tried a few different jetting combinations, and I've installed a heavier flywheel. What's weird is it seems to run lean erratically. I'm running a 48 pilot jet (at about 700' elevation 80-100 degree temps) which should be too rich. It's almost like it has a vacuum leak or something. I've got a Boysen quickshot on it also, but I doubt that's the issue since it doesn't stall when chopping the throttle.

Does anyone have any suggestions on what to look for here?

Edited by RiderX, September 25, 2011 - 06:27 PM.

  • Mr. Neutron

Posted September 25, 2011 - 06:26 PM


Hmmm..... :smashpc:

I've had stuff like this happen to some of my bikes in the past. Once, it turned out to be a messed up tank vent valve (those one-way valves, stuck in a hose that comes from your gas cap). It wasn't letting ANY air in as the fuel got used. Took me awhile to figure that one out..... Had the carb apart a couple of times, & etc.....

I'd start with the basics, and then go from there. Check the aforementioned fuel vent, then your tank's petcock screen, the fuel line, and then, as much as I hate to say this, you may need to look deeply into your carb. :busted:

What year & model of bike are you working on here?


In EDIT: Sometimes turning your idle speed up a little (within reason) will help to prevent stalls. Where are you at on your fuel screw adjustment? Does the fuel screw have all it's hardware (the washer, spring, & o-ring) in, and in the correct order? Just thinkin' off the top of mah punkin head here..... :thumbsup: I'm guessing that somewhere, somehow, your fuel supply or your low throttle circuits in your carb need help. After that, would need more info (how many hours, maintenance done, & etc.).

Also, WHEN does it stall on ya? With the throttle closed (braking/slowing situations?)? Or when ya whack the throttle open?

Jimmie (again...)

Edited by Diesel Goober, September 25, 2011 - 06:35 PM.
forgot to mention some stuff.....

  • RiderX

Posted September 25, 2011 - 06:40 PM


I've checked the fuel vent (I removed it to see if anything changed-it didn't), and I recently installed a new WR petcock. The fuel seems to flow fine when I remove the hose and turn the fuel on. I forgot to mention my bike info, lol. 2009 YZ450F, about 50 hours on it. I guess I need to just mess with it until I find the problem. It does seem to only affect the pilot circuit. Today I rode it for about 30 miles, and it rode fine at first. It started stalling as usual after about 10 miles into the ride, so I leaned the fuel screw from 2.5 turns to about 1.5 turns out. It ran fine for a while, then after about another 10 miles it started running like it was really lean (excessive popping on decel) and stalling even more. :smashpc:

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  • Mr. Neutron

Posted September 25, 2011 - 07:00 PM


Well, I'd probably guess it may be time to open your carb up, and check it for a small "chunk of junk" in one of the little passageways inside it, or dirt in a jet, or ??? Hopefully, that will address the stalling..... :smashpc:

Here's a link to a decent article on how to take apart & clean an FRC MX carb:


Hope this will help ya some!


  • RiderX

Posted September 25, 2011 - 07:21 PM


Nice link, that will definitely help.

  • ttr250dude

Posted September 27, 2011 - 01:21 AM


When is the last time you checked your valve clearences?

  • idahoexcr500

Posted September 27, 2011 - 05:06 AM


i had a similar issue in the hot weather with my 07. turned out to be the tank vent valve. I now run just a vent hose with no check valve. I also had an aftermarket fuel screw that was not staying tight. fixed that too. between the two no more stalling problems. A friend with a WR450 had same issue and it was his tank vent also.

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