Jetting question to JD and Taffy and others...

12 replies to this topic
  • sabin

Posted September 12, 2002 - 10:07 AM


I got today my OBEJP (YZ) needle I ordered before one month ...

I'm now using OBDQR3 (stock):
PJ42 – little rich, but 38 is lean and I got 40 today
PS 6/8 turns

ACV disabled
AP disabled (was o.5 sec)
WR timing (if somehow related to jetting...)

Open exhaust
Lid and snorkel on the bike, too much water crossing...
Riding on about 1000-1500m (3000-5000ft)
Air temp about 18C (65F)

My current problems are:
rought low
inconstant idle
weak top

I have only 200MAJ and also 100PAJ and I’m waiting for 65PAJ. I can order only from yamaha and ASAIK they do not offer smaller air jets.

Please guys help me make some decent jetting with what I have and tell me what to order from sudco internationally. I’ll order PAS for sure :D , but which MAJs, needles … OBF?

I prefer lean smooth setup, economic fuel consummation with nice throttle control and response … “pure nirvana” as Taffy once said :)



p.s. I read jetting Qs, snap … more snap… I need a starting point considering my setup and needs...

[ September 12, 2002, 01:24 PM: Message edited by: sabin ]

  • LarryCO

Posted September 12, 2002 - 11:18 AM


Cant really talk too well about that altitude range as I'm from Denver (5500 - 13000 ft elevation)...however, I can share with you what works TREMENDOUSLY at about 7000 - 9500 ft...and you can go from there.

With that altitude range, I've been using:

Given you're a bit lower, my first guess would be to try something like:
38PJ/65PAJ/EJP#3.5 or 4/160MJ/160MAJ. Another thought might be something like:

I think the reason why you think the 38PJ is too lean is because you've been using it in conjunction with an "R" diameter needle...a pretty thick needle. When you put a 35 together with a "M" or "N" OR a 38 together with a "P", you might have better luck.

Definitely get the pilot air screw and spring from Sudco...not to mention a 160 main air jet. I'd also suggest a smattering of main jets from say 155 up thru 165...that you can play with.

Perhaps someone else from that altitude range or Taffy/JD will chime in with their $0.02 worth...

Good luck!

  • michaeltrundle

Posted September 12, 2002 - 01:46 PM


I would definately get a smaller main air jet if you want to run a 155 main.
Your top end will probably feel a bit flat and dull because its too lean. Go for a 160 maj, it seems to be the popular choice. If you want to keep the 200 maj, I think you you should be more up in the area of 165-168 main jets.
The main jet makes quite a big difference to the entire throttle range on my bike. From about 1/4 throttle up you can really notice changes to the main jet size.
It will probably take you a lot of small changes back and forth before you get it jetted to your liking, hang in there and write everything down as you go, I have tried about 20 different combos in the last 2-3 weeks but I believe it is definately worth the mucking around to get the performance that is available simply by tuning the carb properly.
After a the first dozen or so times you pull the carb off it starts to become a bit second nature and a 10-15 minute job.
I,m sure taffy or one of the other jetting gurus can guide give you the right advice as long as you provide good descriptions of the symptoms you are experiencing.

  • Hick

Posted September 12, 2002 - 06:56 PM


Originally posted by sabin:
Lid and snorkel on the bike, too much water crossing...

If you think about it the snorkel is giving you all of about 2" of extra protection.

I realize that a good amount of water can pour into an open air box during a fast and relatively shallow water crossing, but that is what the air box drain is for (which is plugged on the WR).

I think the only real function of the air box lid is to make the WR quieter.

But I live in the desert, so what would I know about water crossings?

If you want to order another needle try this one:


That is the Yamaha PN for an EKQ.

It isn't clear from your post what your current jetting is really, have you tried the "E" needle yet or not? That will have an effect on most EVERY other jetting spec in the carb.

Nevertheless I think a good starting point for you would be:

40 pilot
65 PAJ sounds good to me, but get the PAJ screw anyway.
160 main
200 MAJ should be close.
EJP #4 should be close also, #3 may work better.

Going back to how I started this post I must put a disclaimer here that I've never bothered to jet a WR with that silly lid and snorkel on the air box, so, like water crossings, I'm pretty ignorant of the effects of that stuff.

Hope this helps.

  • James_Dean

Posted September 12, 2002 - 08:00 PM


The suggestions look good from everyone.

I also question whether the Exx needle is a good idea with the airbox cover on. Try removing it if possible or the Dxx needle may be as good or better.

To summarize, as an estimate-
40 pilot
65 pilot air
OBEJP#3 (or #4)
160-165 MJ with 200 MAJ (or 155MJ w/160MAJ)

Make sure you don't have any air leaks causing the irregular idle. A richer mixture screw setting may help control the idle speed.


  • Taffy

Posted September 12, 2002 - 09:26 PM



i jetted a couple of WR timed bikes in europe and they did the following;

DTM needle on clip 4
1.5 turns

this is for mud and crud, good trailing, and good reaction everywhere.

if you put the E series in i would go
160 MAJ
EMM in clip 3
1.5 PS
a spit of APJ.

whatever you do you have the confidence that these lads got it right for themselves and you're heading in the right direction.


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  • sabin

Posted September 12, 2002 - 09:30 PM


10x guys I will try your recommendations today and report tonight.


I’m using D needle up to now. I’ll remove the lid and put the drain end that I have from my old XR6.


  • sabin

Posted September 12, 2002 - 10:34 PM



Do you mean that the D needle gives better traction than the E ?

Unfortunately I cannot order 160 MAJ for now and I mey need to stick to 162MJ/200MAJ. Can I balance that somehow with the needle?


[ September 13, 2002, 01:38 AM: Message edited by: sabin ]

  • Taffy

Posted September 13, 2002 - 04:07 AM


the needle is a little less agressive at higher revs. the D series are excellent in europes wet winters and for trail riding.

the needle taper starts higher (or sooner as you open the throttle) and so in first and second you can carburate cleaner.

it's probably the roll on in fourth gear at 80kph that you'll notice only the mildest drop.

let's be honest the parts are cheap enough to afford both.


  • samohT

Posted September 16, 2002 - 01:00 AM


Originally posted by sabin:

Unfortunately I cannot order 160 MAJ for now and I mey need to stick to 162MJ/200MAJ. Can I balance that somehow with the needle?



I don't know if you know this, but according
to sudco the FCR MAJ is the same jet as the MJ
for the following keihin carbs:
For all Honda VB, VD, and VE series carbs.
Honda, Kawasaki, CV and CVK Series carbs.
Some Honda PD and PE Series carbs

Perhaps this will help you find a 160 MAJ.

  • sabin

Posted September 16, 2002 - 08:16 AM


thanks samohT!

Thant's a great idea!

  • YJ

Posted September 16, 2002 - 09:15 PM


Originally posted by Taffy:
i jetted a couple of WR timed bikes in europe and they did the following;

DTM needle on clip 4
1.5 turns

Do these settings also apply for 426s?

I can see a lot of jet sizes, screw positions, AP-timings being traded here, but most of them seem to refer to the 400. Does the 426 require the same values or is there some rule of thumb saying someting like "and for the 426, make that +10%" ?

I took my WR to the mech yesterday, for inspection, service ('t was about time after 5000km without oil change!) and - if needed - rejetting.

Called the guy in the afternoon, he stated that this my '01 was running stunningly well and that he'd not see a lot of work to do.

Nonetheless, when rolling downhill through a canyon after rain (wet road, high moisture, temperature fairly low, not over 15°C), she'll sputter, bark, bog an just won't do anything besides idle (stable, starting also good) and full throttle. In these wet conditions, one generally prefers to stay in the lower 1/3 of throttle...

Same happens when coming down alpine passes (>2000m) in wet conditions (when we have to ride in the clouds and the mist), or on rather high altitude (2500-3000m) in the Italian alps. Above 2500m there's misses, bogging and throttle response tends to become "digital", full or nothing.

As I understand from what I've read so far,
I'd say the bike runs waaaay rich. Fuel consupmtion is around 6l/100km, and it rose way
beyond 8l/100km in the Italian alps.



  • Taffy

Posted September 16, 2002 - 09:34 PM


the missile is from switzerland!

he was the first to try my settings. yes they'll work for a 426 just the same and a 450 come to that. the reason i say that with confidense is because i know that there might be the smallest difference between the models but nothing that can't be sorted in twenty minutes.



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