Pilot Jet Screw ? & stuff 03WR450F 160MJ, 48PJ

I was just wondering whether running on clip 1 is a good idea. I currently have this 38 pilot, 55 paj, 155 main, ekn #1, 160maj, fuel screw 1.5, no APJ. It runs well but I think I can still get more out of the mid range (feels a little fat). I assume that a 150 main and putting the clip on about #3 or #4 would probably tidy this up. Your opinion?


EKN=1 is equal to EMM=2 and yet i ran it on 5 so i think we shouldn't be 3 clip positions apart.

i think if you're on an open pipe that 150MJ at sea level is bordering on lean.

if you have a vortip and you live 3-5,000ft+ then i guess it's ok. however you should try slightly more air in the PAS at 60 or 65 OR try a 35 PJ.

i think that you should do the bump and grind yourself and try the different settings


I am at sea level with an aftermarket exhaust which breaths only marginally more than the stock euro/aussie item. I will try putting the needle back to #3 and turning the PAS out a bit more. Thanks.


Im riding at between 1500' and 3000', temp 35-50. Bottom end response is sluggish at best. Haven't removed snorkel YET but will before next ride. I know this is probably jetting 101 but I'm new to pumper carbs. Also, any thoughts on the fuel mix screw from zipty racing? Can't seem to get a call or email back from those folks. Any thoughts would be much appreciated.

You may be able to change the jets in 20 minutes after the FIRST time you remove the float bowl! I had to take the entire carb off and "gently" tap the screws on the bowl to get them to come out. I almost stripped them trying to remove them while the carb was on the bike. Be careful with the plastic Hotstart it strips easily. Thanks to UTVOLS on the gouge . I got the 72 starter jet in last nite . 19 degrees F. and it started first try on the e-start, with a dry bowl. No backfires :)

Finally got to the track. Jetting feels great (see sig.). NO OFF IDLE BOG! :) Probably could be tweaked a little better but don't have time now. Takes several kicks to start at ~40F, but I've got to rem to turn the gas and power on and blip the throttle 3 times. After putting new springs in, front is still too soft. Added more oil, will see this coming weekend if that helps or may have to re-valve.

Can anyone provide some clarification on what needle jet Motorod is using (as listed in his sig)? Is this some new type of needle specific to 450's (NDJN) or is he referring to using a DJN needle (N diameter, 0.75 degree single taper, etc.)?

I also see they've changed the part number classification for 450 needles...using 5TA as the prefix vs. the 426/400 classification of 5JG... Any idea on what this means?

Finally, Motorod...I cant believe that a 48PJ with a 70PAJ and N diameter needle works very well for you. 70PAJ sounds extremely rich when used with a 48PJ. I not trying to critique here...just getting a feel of how different jetting a 450 might be vs. a 400 or 426...

Just want to keep up on this stuff...



First thing I did, before I started the bike, was put a 48PJ and a 160MJ in as UTVOLS had suggested, and took the cork out, & Baffle out. It still had an off idle bog. Then I changed the needle for 5th clip, 1-1/2 out on PJS, & 1/2 turn out from stock on squirt. It ran bad, backfired when giving it gas in neutral, and still had the off idle bog. Then I replaced the stock needle with the 5TA-14916-JN-00(#NDJN) 4th clip. Now it runs great with no off idle bog. The needle size I got from a sheet my dealer gave me and it said it was the YZ-450F stock needle. I know this does not match the YZ manual, but that is what the dealer's paper said. The 70PAJ is stock, and Taffy suggested I leave it in for now, because I had made so many changes with out testing it.

The only problem I have, besides suspension, is it is little hard to start, but once it warms up, no problem. I think I just need to get use to starting it, but I do have a 72 starter jet ordered (another UTVOLS suggestion). I have also been looking for a chart or something on these needles, but have had no luck so far. I have the same questions you have?

Finally, some camps go with the larger PJ/PAJ ratios for tractor like torque. Others go with the smaller PJ's/PAJ ratios for a "snappier" throttle response.


I cannot understand what do you mean by PJ/PAS ratio. Can you please clarify which is torque and which is snappier. For example with

40/65PAS and


Isn't leaner = snappier and richer = torque?


you'll be good for a PAS and a ratio of 40PJ and 75 (or 70 PAJ!)PAS.


why do you suggest different PAS(75) PAJ(70)? Is there any difference when using pas or paj?

Are you still using euro pipe and was it -5 on the main?

I want to compare my jetting in my elevation and air temperature with JDs .xls, so can you please provide temp and altitude info for your jetting?



first of all i sold the bike 14 months ago.

i am at sea level.

the difference in air is minimal between a #70 and #75. air is so light etc.

glad you pointed out that 70PAJ wants about 40PJ. this will work as long as the needle straight is not too 'fat' so it should be a M, N at sea level and whatever crazy needles you all use at 10,000ft! (P, Q).

there shouldn't be a difference between the PAJ and the PAS-we all hope not anyway!

my euro pipe meant that i was about 8 lower MJ than if i'd run a YZ pipe. but don't forget that i ran a 160MAJ which reduced my MJ by 10 anyway.

so if i'd been running a 200MAJ my main would have been a 160 and if i'd had an open pipe it would have been 162-165? (with an 'E' needle).


Hi all,

these are the settings i intend to use in my new WR450, euro specs, fully uncorked, air box mod done, akrapoviç full open pipe, yz exhaust cam. Can you give your comments??

-needle #CVP (yz450) 5TA-14916-VP clip 4

-PJ 40

-PAJ 70

-MJ 168

-SJ 72

is there a main air jet (MAJ) on these carbs?? :)

All input welcome!!


:D :D

Main Air Jet (MAJ)= dia.;2.0 stock

I think your MAJ is too rich but I think my PJ may be too rich also. Let us know how it works. Check my sig. for my current settings. :D:)

what up?

I got a wr400 and someone told me about a deely you can bolt on your carb that will shoot air under your slide and give considerably more power. I think its made by DSP

does anyone know any thing about it? :)

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