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WR400 vs. WR426 Carburation: Same or Different??

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I have a European WR426 - 2001 and after reading so many articles on timing changes in this great website, I have created courage to change my WR timing to YZ timing the following weekend.

It seems evident from reading that I will have to change jetting specs accordingly. I have previously consulted the innumerous number of articles posted herein on this issue, which mostly talk about WR400's, so one important question remains unanswered:

IS THE WR400 JETTING SPEC COMPARABLE TO A WR426??? I have seen contradicting answers in this site. May I ask the GURU's amongst you what is the corect answer to this question.

I am not a jetting specialist, and since I also (simultenously) will change the YZ muffler for a WB-E series pipe the same weekend, I am about to have a LOT OF JETTING experimenting to do.

I would therefore also VERY MUCH appreciate if someone (the same GURUs amongst you) could give me a hint as to where I should start this re-jetting endevour (in terms of jetting, #s and clip position), in order to leave more time during the weekend riding my revamped "blue thunder".

Here are the specs of my bike and riding conditions:

- Airbox lid removed

- No Grey Wire (european bike)

- Orginal air-filter

- WB E-series 12 Disks

- Riding Altitude 4,000 feet (=1300 mtrs)

- Weather conditions Warm (80F or 27C)intermediate air humidity

thank you VERY VERY much in anticipation for your help, and whenever one wants to ride in BRAZIL let me know, I am glad to help :)

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I just changed my WR 426 to YZ timing. I went on the technical side and looked up jetting specs from around the world. I had a DVP needle so I checked to see what everyone w/DVP needles were running. No one w/a WR 426 YZ timed, had listed their jetting. So I had to go w/a few 2000 WRs running DVP needles all w/the clip in #4. Most were running a 48pj and 165 to 170 mj. I tried all combinations of these along w/a 42pj. They were all way too rich.

I ended up w/a 38pj, 160mj, DVP #5, PS two turns out. The bike rips until 5th gear past half throttle it excells a little slower. I suspect because of the 160mj but if I go larger it is too rich down low.

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The '00 WR400 has the same carb as the 426. The 98-99's have a slightly different carb. yes, jet settings are slightly different, too! However, the same bikes in the same conditions may require difference settings. This is where it gets interesting :D

Since you're riding at high elevation and it's warm, think leaner jetting than what some of us are running.

What would I start at?

Stock or close to stock YZ426 settings, with some other jets handy.

I really don't know what these are anymore for the YZ426, but here's a shot on where I would start

--EKR needle, 4th clip with 162-165 main

or EKR #3, 168 main jet. Some experimentation between the clip position and main is going to be required. There are other more aggressive needles, such as the EKN and FHM you may want to purchase and experiment with, but the EKR (leaner than the EKN) may suite you pretty well.

Leave the pilot jet alone for now. Adjust the fuel screw so that is pops slightly when deaccelerating. You don't want it to backfire or pop loudly. Adjust it out when it gets colder or lower elevation riding, adjust it in when it gets hotter or when riding at higher elevations.

A 42 pilot is probably going to be your hot ticket, but a 45 should be experimented with as well. Please note, you'll have to re-adjust the fuel screw if you change the pilot jet.

Hmm..what else? Change one thing at a time. Start with the needle. Then change the clip. Then experiment with main jets and re-experiment with clip position :)

While you're doing all this, clean the carb out really well! Also check the float height if you can.

I believe the EKR#3, 168 main, 42 pilot w/ #75 main air jet will suite you. However, I would also try EKR#4, 165 main as well.

Buy one of the jet kits with 5 jets in series included. I will say your WR is going to be a different animal after these mods!

Good luck, and let us know how this goes!

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i think this looks like a tragic accident about to happen.

brazil wants to make two or three changes at once which you should discourage straight away but didn't.

you just can't go around recommending jetting that isn't there yet. if it's not right don't put up anything no matter how tempting it gets.


i can't believe that an **R needle is your recommendation and then tell brazil not to touch the pilot circuit. he should fit an EKP or an EKN. he should do the main jet first not the needle and the 75 is the pilot not the MAIN air jet.

the new carb appears to have made virtually no difference to the jetting between the two.


EKP or EKN needle on c4



38 pilot jet.

this is baseline jetting. don't forget to cut your APJ either off like me or turn it down to .5 seconds using the BK mod.

make one change at a time. do the exhaust then do the jetting. then do the YZ timing. you should allow at least a week of riding to get the jetting for the pipe right. the YZ timing will want barely any jetting changes.

if you're too lazy to work on the bike, to get it right then don't touch it. hopefully you're ready to spend your money on having a good selection of jets ready. try to buy the PA Screw that so many people talk of.

i know lads, i've slapped you on the hand but no matter how many times we say it, if it's not the right info people are going to disappear up their own arse which in brazil means that at least we know where the poor little sods disappeared to (political point thrown in just to get the juices flowing)


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