More Jetting help please, bike dies with twist of throttle

Denver altitude, recently went from the following jetting:

DVR 4th position

175 main

48 pilot

1 1/4 out

to this jetting:

DVR 3rd position (I will not have the EKQ for a while yet)

170 main

45 pilot

1 1/2 out

The bike starts and idles fine with the choke out during warm up. When the choke is pushed in, it idles roughly and sometimes dies. When I twist the throttl, fast or slow, it dies. (the first 1/8th is OK but after that is kills it).

It feels like it runs just a tad bit better if I take the fuel (air?) screw out. Up to 3 turns.

It was running fine with the richer jetting but many thought that was way to rich for the Denver alt. Any ideas? Does my bike like a richer setting for some reason? Do I need the 48 pilot? Please help. I have a trip to Moab this Friday.

Thanks, Doug

[This message has been edited by Dougie (edited September 30, 2001).]

doug, i'll try here but as usual the guru himself may know better.

your very, very lean on the needle straight.

you've leaned off 1/8th throttle.

i would suggest that you try turning the pilot screw in or out a full turn and i think that turning it right in it will help.

if you read patrick burns write up YOU MUST GET THE NEEDLE STRAIGHT CORRECT before you do anything else!!!!

if i in the UK use a _ _ M or N and i'm told that you have top be slightly leaner (altitude)-you should be on an _ _N or P at most. not a Q and most definately not an R!

change that order to a EKN or JD will say i presume -an EKP then with the bike richer at "idle" + ;you THEN can lean the 1/8-1/4 throttle.

to do this

your PAJ and PJ work independantly at the same time so if you do go for the above needle, get a pilot air screw to replace the pilot airjet you will be able to lower the AIR as well as the fuel at 1/8-1/4 throttle. 48 to 45 PJ and #100 to #75 PAJ, ok?

your PAJ is i believe a #100 and when you purchase the PA(j)Screw turn it down to #75 and i think you'll be fine.


I would go back to the #4 clip. Keep the 45 pilot & 170 main and work from there. The DVR should be workable, you were already having success with it.

My preference would also have been to use a DVP or DVQ needle instead at your altitude, of the "D" taper needles, or any E-Q of the "E" taper needles.

I'll give that a shot.

After it warms up, I can get the revs up by VERY slowly twisting the throttle. When the revs are up, it starts backfiring in loud quick pops.

Otherwise it starts fine, idles OK with choke open, idles roughly with it closed. Then after that a slow or quick twist of the throttle kills it.

Thanks guys.

Ok I went back to the fourth position on the DVR. It seemed to run a little better but still eventually died. I was able to twist the throttle without it dieing right away but it did seem to back fire quite a bit. Plus I think the plug may have fouled.

I am currently at the following:

DVR 4th pos.

170 main

45 pilot

1 1/4 out

One choke note, it idled fine with choke on until it warmed up then it really idled very fast. After the choke was off it eventually died.

Try the 42 or 38 pilot. Should do the trick.


man this sounds like the problem i had just recently. I had the part that goes on the slide upside down and it ran exactly like your talking about. I put it the right way and it runs great.

j dean and taffy suggested this could be the problem



FWIW, today, I took my bike on its maiden voyage with the EKQ. The bike ran great! I have it on clip pos 3. My main jet is considerably different than yours at 158 as is my pilot at 42. If these bikes "Liked" to be rich at our altitude, my jetting should not work.

Also, backfiring and sputtering were almost completely gone too. My ride today was at 4800 feet and it was about 75 degrees out.

Keep in mind this jetting works with my restrictive pipe. I didn't try it with my free flowing pipe yet. But, even when I run the FF pipe, the only problem the bike has is sputtering at constant revs.

Good Luck!


i'm on the EKP clip 1 as of today!!! (EMM #2)

pilot is on 40 and looking at 38 next

155 MJ and looking to go back to 158.

PAJ is 3/4 turn of PAJ Screw (#85)

we're very close. i believe that at altitude you need to be leaner than me. so it doesn't bear thinking about does it.

your 42PJ is about right for a _ _Q needle straight in my opinion.

that just leaves the needle and the MAJ.

look in search and put in "aussie andy" in the lower username and look for a long thread on the MAJ project.

bar the needle clip and the MAJ we are running very close!

i have no APJ at all before i forget. the other thing is that i have my own "taff timing" cams and so that means you need to be a clip and MJ richer i would think.

want to try that needle down and see how sharp it is?


[This message has been edited by Taffy (edited October 01, 2001).]


I too live here in Colorado...riding with a buddy of mine quite a bit at Rampart Range. I have the following setup that runs just fine for me...

-155 Main

-Stock Needle Jet...clip position #3 (too many 3 letter acronyms..cant remember what's stock!)

-Stock Pilot Jet (is this a 42?)...approx. 1 1/2 turns out if I remember correctly.

I have a little bit of jetting experience with some of our 13000+ ft rides in the I could talk to you about that as well if you're interested. Finally, there's a spreadsheet that my friend Jim got from someone out there on TT showing jetting changes for different altitudes/temperatures that I could share with you some rough guidelines to adhere to, as it appears that everyone's bike has it's own "personality"...

By the way...WR timing, uncorked, air box lid sometimes on/off (depending on riding conditions, and if I think my buddy's going to take me through that "stream" on trail 649/650!)



2001 WR426, Brooks YZ tank, SDG seat, gray wire cut

I'm seriously thinking of going back to the 48 pilot and 175 main just for this trip. At least it was running then. Maybe not dialed in but running. I'll get it straight after the trip.

First, I am going to take it out to Watkins on Tue afternoon and try some different setups their. May try the 42 pilot at this point. Keep in mind I am fully modded with all free unrestrictors plus FMF Hi flow pipe and PC IV muffler. I am also YZ timed.

LarryCO, I think I met you about a month ago out at Rampart. I was riding with some two strokes and you were with two other guys. I had the WR 400 that looks like a YZ now.

My buddy is like why did you mess with it? Cause I'm always trying to learn and get more out of it. He is right though, I should have waited.


Yep...remember you. Followed you and your boys down that technical stretch of 'slickrock' type terrain. Remember trying like hell to convince my two friends to try it...finally did...and gladly so. Looks worse than it really is...

Drop me an email @ and I'll send you that spreadsheet I was referring to. Now once you start screwing around with the pilot air jet, all bets are off with 0 - 1/4 throttle jetting. The spreadsheet really didnt help me too much with the pilot jet...more with the needle jet and main jet.

Regarding Moab, enjoy mucho! I'll be heading out to Fruita, CO sometime in late Oct...nice, but not quite the same. Check out the Kane Creek and the Poison Spider/Gold Bar Rim trails. Pretty awesome rides...especially Kane Creek. On Gold Bar, there's a 5' deep, 4' wide crevice that I've found my bike fits very nicely'll know it when you see it. Look for the blue paint on the ground... :)



2001 WR426, Brooks YZ tank, SDG seat, gray wire cut

Larry, have you ever done the Hare Scramble series up at Berthod? It gets going here at the end of Oct. Let me know if you are interested.

I'm pretty familiar with Moab. This is my seventh trip. I am 2 out of 5 on the Gold Bar crack. Made it over all 5 times but only twice with both wheels on the ground.

I'll shoot you an email soon. Doug


Did you have the carb slide out during your jetting change with the flat plate that goes on it? (read higgy426's response)

If the plate was installed upside down then all you have to do is put it back correctly.


I'm also interested in the Hare's at Berthoud, can you tell me more?



I sure would be interested in hearing more about this harescramble. Actually being able to participate in it is a different story though. Funny how a 6 month old daughter slows your life down a bit! :)

I'll await your email. If you get a chance, any other good Moab trail recommendations are always welcome.



2001 WR426, Brooks YZ tank, SDG seat, gray wire cut


Follow higgy426 and James Dean advice your the plate on your flat slide is upside down. I bought a used 426 with the plate upside down and it took two months to figure the problem out. E-Mail me at and I'll send you a diagram of the carb.

I never pulled the slide this time so if it is upside down, it has been that way for over a year and 1/2. Oh man I hope not, that would be :)

I went back to what should be the way too rich jetting for my trip. It is running again. I'll mess with it when I get back.

CO guys, the Hare Scramble series at Berthod if a 5 race series Oct through Feb. It usually is an approximately 6.5 mile course with a lot of turns. They run it on their track and the small trail system in the behind the track. It is 2 1/2 hours straight. They have several classes. I run the Vet class 30 to 40 years old. It costs about $35 to race ($25 for the race, $10 to get in the track). They start about 10:30 with a two hour sign up period before.

Larry, I feel your joy and pain. The joy of an 8 month old daughter, the pain of limited riding. But it is so worth it. I only expect to get 1 or 2 races in this year. But I've only been able to run 1 in each of the past two years due to schedule and cold WX. I'm a wuss when it comes to racing in the cold. I'd rather sit on the couch and watch football.

Here is their website,

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