2001 YZ stalling?

I have a new YZ426 and it consistently stalls in two cases:

1. In slow, nasty, tight sections (desert 2000-4000 ft).

2. When I lock the brake in sandy berm turns (desert/motocross 2000 - 4000 ft).

I run an E-Series WB exhaust and I've tried various needle and main jet setting with no avail.

I heard an R&D accelerator pump cover would help, but I'm more suspect of the low-speed jetting settings, because it stalls when I come off the throttle or crack it fast.

Any suggestions?



roll on the pipe instead of just twisting it..

if this don't work buy a 2001 husky 570, from what I read the bike fly's..

would make a great desert racer..

I had the same problem with my '01 and cured it by going to a 48 pilot jet and raising the idle speed slightly. This allows you to twist the throttle vigorously without inducing "flame-out" on the engine. Also see

James Dean's posts on adjusting the accelerator pump to further refine your throttle response.

Same problem here. Once, I came off the top of a long hill, got 3 or 4 feet of air and it stalled when the rear wheel hit the ground. I guess I should have nailed it.

I don't thnk there is really a whole lot you can do about it, except raising the idle speed, like "vznx1w" said.

When your RPM's drop real low, it'll stall(short stroke and high compression).

Just my 2cents.

Any other ways to prevent stalling I'd appreciate hearing about too!!


I'm 15, live in MI and ride a '00 426F

YZ 426's suck!(all the air they can get)

I have the same problem. IMO this isn’t a jetting issue, although if your bike isn’t running clean on the idle and/or pilot circuit it will of course be easier to stall. The way I see it you have two options:

1) Turn up the idle and use clutch sooner, hold it longer in corners (this is what I do).

2) Get a flywheel weight (this is what I should do).

If I really whack it open my ’00 will cough but not die, if I brake too soon/hard and clutch too late/short it will stall regardless of how slowly/quickly I roll the throttle on. Don’t spend $$ on the R&D plate until you’ve exhausted your jetting options.

As for jetting to get rid of the cough, you may try richer idle mix and maybe a 45 pilot (you’ll likely need to reset your idle mix if you change the pilot). A lot of the WR guys run YZ timing and jetting, James Dean is a jetting guru w/ a WR and the WR side of Thumpertalk gets more traffic so for more jetting tips you may try a post over there.

I ride at 4,000 ft., ’00 YZ w/ PC T4, bored to 444 w/ 13.5:1 Wiseco

162 main

45 pilot

1.75 turns out on idle mix

EKP #4 (EKP is just like your stock EJP, mine is just a half clip position leaner).

My jetting is always a work in progress type of thing though.

Another throttle response tuning option is accelerator pump timing. I ended up delaying the pump operation on my ’00 by ¼ turn and this helped my throttle response (keep in mind that the accelerator pump was redesigned for '01 to have a shorter pump duration). This is done by turning a spring-loaded screw just under the slide pulley on the right side of your carb, under the black cover, turning this in delays when the pump starts. Click here to read an old post from the WR side where James Dean explains how this works. It is pretty easy, ¼ turn makes a noticeable difference and if careful you can always put it back to the stock setting.

I hope this is helpful…

Well the problem might not have to do with jetting at all. If you're stalling when slamming the brakes on in hard corners then you could be slowing the engine down enough so that it'll stall anyways. Just like how newbies seem to never give enough throttle when letting the clutch out to start moving. Just my 2 cents

lower the footbrake a tad- it works a treat.

secondly, the flywheel weight that hick mentionned is ace-o-lux & for $30 or so from stroker you've got no excuses. i ride a wr which someone has said is 10oz heavier already. i added 10oz & it's lovely. i'd try the 12oz version.


One more thought on the stumble just off idle that I'm not sure if anyone has mentioned. You might try raising the needle (lower the clip) one position to see if that has an effect. Just a thought.

Try to avoid using your rear break.It takes some getting used to; but, once you learn to use your front break you'll love it.This will avoid stalling and improve traction. Also, in tight corners, you should try using your clutch a little sooner and roll the throttle( don't snap it open).

IMO, I think you should ride the hell out the the bike and try different riding techniques before you begin wrenching it.

[This message has been edited by thumpdaddy (edited 02-07-2001).]

It's been a while since I originally posted a response to the many suggestions, but this is what solved my problem:

162 Main +

45 Pilot Jet +

4-clip on the needle +

increased the idle = 2nd Open Expert finish at CRA (World Off Road Championship Series)

Thanks for all the suggestions.


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