LarryCO Jetting WR 426


Tried jetting my 2002 WR 426 has per your signature with poor results.

Starting point was

42PJ,75PAJ,DRR-3#,155MJ,200MAJ,PS2 1/2

38PJ,65PAJ,EKP-3#,152MJ,160MAJ,PS1 1/2,BKmod .5 sec

bog at 1/8 to 3/8 throttle, 3/8 to full throttle rips

no snap wheelies :)

38PJ,65PAJ,EKP-2#,152MJ,160MAJ,PS1 1/2,BKmod .5 sec

no much effect

38PJ,65PAJ,EKP-1#,152MJ,160MAJ,PS2 1/4,BKmod .5 sec

popping on deceleration loss of power at 3/4 to full throttle

38PJ,65PAJ,EKP-1#,155MJ,160MAJ,PS2 1/4,BKmod .5 sec

Popping on deceleration 3/4 to full throttle popping on acceleration

Next try will be

38PJ,65PAJ,EKP-3#,150MJ,160MAJ,PS1 1/2,BKmod .5 sec

I bought James Deans jetting guide, which is more info than I had before, but the guide doesn't take into consideration changing of air jets. Since the PAJ on a WR is a 75 and an YZ is 100 where's the baseline. Can you pass along numbers used in your jetting guide?

Thanks JD

I am unsure as to what elevation you ride at.

Here is what I am running:

45PJ (42 was stock), 75PAJ, Stock needle #4 position, 168 MJ (165 was stock), 200 MAJ, PS 1-3/4 (2-1/8 was stock). I am also running a hotter spark plug.

My 02' WR 426FP has the gray wire mod, baffle out, and lid removed. I ride anywhere from 4300 ft. to 8000 ft.

Sounds like you are going the wrong way. Too lean..........


What altitude are you riding at? What exhaust are you using? Are you running bad gas? Carb and air filter clean? Are you sure your BK mod is 0.5 seconds (I had to "reset" mine as the screw shook loose and lengthened the throw of the accel pump arm back to about 1.5 secs squirt).

I just ran my "low altitude" jetting setup (see my sig below) at Rampart on Sat. and it worked GREAT! No bog whatsoever. If anything, it was a bit lean on the upper end, and I should have gone up on the MJ a few...but otherwise, ran fine. The only problem I had was keeping the bike upright on the icy spots! :)

Write back with some more info and we'll see if we can get you running better. I dont think there's any major differences between the '01 and '02 carb, so assuming similar setups in terms of exhaust and altitude, you should be running better. If that's the case, try going up on the MJ to about 155 or 158 and see if richening it up a bit helps with your 3/8 throttle hesitation.


I just did mine to LarryCo's settings and it made a huge difference. One mistake I made originally was not letting the bike warm up completely before I changed things.


Guess I foregot a couple of things.

My setup is very simlar to yours. 2002 WR426, WR timing, uncorked stock exhaust, gray wire cut, throttle stop mod, BK mod 0.5 secs, airbox lid removed, BK mod screw has a drop of lock tight (found this out the hard way with a YZ last year), 91 octane gas, just cleaned air filter and new spark plug.

I ride alot at Rampart 7,000 to 9,000 feet mainly because its close to home in Sedalia. Have never rode at the track with this bike. Also rode at Rampart last weekend and got a little agressive on ice.

There's no way to could run with r1superstar settings, the hotter plug must be compensating for the very rich settings.

I didn't have much luck with the EKP needle when I tried it. I didn't have the PAS at the time though. I now have the PAS and have it adjusted to 65 but haven't been able to test it yet since I'm waiting to get my radiator (thanks John). My current (untested) settings are in my signiture. I used the same settings with the stock PAJ and they worked great.

It sounds like you went from too rich at 1/8 to 3/8 throttle and moved it to being too rich at 3/4 to WFO by moving the needle. Try setting the EKP back to #3 and then double check to make sure the PAS is adjusted to 65. If it is then you might want to lean up the PAS a little more to eliminate the bog at 1/8 to 3/8 throttle. Hope this helps.

Could some one please explain what the EKP and PAJ are?

EKP is a type of needle. The E series of needles have a different taper than the stock D series WR needle so it changes the power delivery similar to that of a YZ. PAJ is the Pilot Air Jet and PAS is the adjustable Pilot Air Screw which replaces the PAJ.

try decelerating in fourth without changing gear and no brakes, just decelerate and decelerate using that one gear from top revs down to stalling.

NOW where does it pop back. this is the proper way to check wheteher it's the MJ, the needle or the pilot circuit (PC).


There's no way to could run with r1superstar settings, the hotter plug must be compensating for the very rich settings.

:) Why not!? I put the hotter plug in after I ran with the stock plug and this jetting configuration. I also have the stock needle in there as well (DRR). It runs FANTASTIC!! Keep in mind that not all Motorcycles are creeated equally. Just my iput. Good Luck with your jetting...........db


Try Taffy's suggested test and report back any results. Do make sure the bike's warmed up though before making a call one way or the other. We'll get this sorted out for you. Although bikes do tend to run differently, I'm still confident that you're very close to having a great runing machine! Wicked's going to get there soon too once he gets his radiator straight and when the snow melts... :)

Wicked, do me a favor and try that EKP needle again when using a 38PJ/65PAJ combo...I think you'll like it. I cant remember back that far but I seem to recall having the same problem you did when using a 42PJ/75PAJ with the EKP. I use the 38PJ/65PAJ/EKQ for super-high riding (like in Crested Butte or St. Mary's), but also rode with it at Rampart and it did OK.

Let us know what you find out JD...


Will do Larry, I just can't wait to hear that thump again! :)

Thanks for the response. I'll try the new setting and get back. Unfortunately, there is now 9" of new snow at Rampart and will have to wait until the week-end and try setting at the track. :)

Thanks wicked crash, you guys have been a big help, I am a newbie and could use some help on the jetting, I am currently running #160MJ, #42PJ, Stock needle #4 and PS 1 and 5/8 turn for Rampart, What change can I expect with the LarryCO settings? Where do you reccomend buying the PAS and EKP? Thanks Again for the help.

You can get the PAS through SUDCO

1-800-998-3529, it cost me around $20 after shipping. Local dealers have no idea what the PAS is. You can get the EKP needle through your dealer. I haven't been able to test Larry's settings yet, my bike is still crippled, but I don't doubt that they work great. The settings in my signiture (with a stock PAJ rather than PAS 65) have worked great, but I wanted to see what a difference the PAS made. I'll let you know how it runs as soon as I can test it.


Using the 38PJ SIGNIFICANTLY helped make the bike more snappier and more responsive at lower revs. The E series needle (like my EKP) was the biggest difference of all in that the bike now explodes through the midrange...even though I dont have YZ timing (which I think I'm going to do someday).

Pick up a couple more things as well...such as a 160MAJ. It'll help your top end. Also, while you're at the dealer, grab an EKQ jet needle as well. If you find that the EKP works awesome for you at Rampart (which you should), you'll find that it's too rich for super-high altitude riding (over 10K ft like in Crested Butte or St. Mary's/Georgetown)...and you'll want an EKQ.

Just my $0.02...

May we get another 2ft of snow soon and have it all melt very quickly!


Thanks for the info LarryCO, I will let you know how it turns out when it warms up, now that winter has finally arrived. Ever ride Moab? Any suggestions for jetting there? We try to make at lease two trip out there each year. Thanks Again :)


If I do anything, I go up to about a 158MJ. Tat's about it. Runs great out there as well...(using the lower altitude jetting in my sig)...

Dont know about you, but I have 18" of snow (atleast!) on my deck now (in Genesee). Gonna be a while for any riding... :)

Hey Thumpers :D

Ive been using LarryCO's 6-10k jetting settings with an EKQ needle both at the Berthoud track and Rampart and have no problems. Power is there when I need it. Could probobly do a little tweaking on the jetting but I have to thank LarryCO for posting them. Without them, my bike would still be running like crap. :D BTW, I own a 02 wr426.

LarryCO, maybe you have some suspension settings that kick butt too :D:)



Glad there's another satisfied customer! Thank Taffy though for the changes...he's the source that helped me...

Suspension changes are for this spring. I weigh 155 lbs wet and there's definitely some improvements to be made from stock. I'm also looking for some sort of fold-down stepladder that attaches to the bike so I can get on/off of it! :)

Try that EKP needle sometime. I think you'll find it slightly better around town and at Rampart than the EKQ. You'll have to change clip positions when riding above 10K for that EKQ anyway, so you might as well use a slightly better jet needle around here.


Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now