Thanks JD/Taffy

I would like to thank you both for keeping up on the carb tuning and posting your results here. I bought a 01'WR in May and immediatly did the airbox, stop and exhaust plug mods. In July I YZ timed it and did the grey wire mod. The bike has always ran pretty good but I knew it needed carb tuning. After a few days of looking through your archived posts, taking notes and reading the Patrick Burns article I decided todig in. I work at a MC dealership so last Monday I dug out the Sudco catalog and made an order for jets and a needle. I received the parts Thursday and started doing the mods Friday. I installed the new needle(EMP) removed the MAJ, went up one step on the main,installed the PA screw and did the BK mod all at one sitting. by Saturday the bike was running like a completely different machine! The carb tuning by far has been the best improvement I have made. Your knowledge and months worth of work have turned my carb tuning into a weekend project. Thanks! grin.gif

I will install a street tire this winter and fine tune it on the dyno at my work place. I will post my results!

4600 ft. altitude: A/F mix screw 3/4, pilot 42, PA screw 1 turn, EMP#2, 168 Main, MAJ removed, AP timing ok and set stroke by cleanest feel while riding in various situations. (approx. half the stroke as stock)

What kind of dyno do you have at work?

I didn't do a baseline run before I put my bigbore kit in(amongst other things...)

My bike is at the tuners (Dale Lineaweaver)

getting the carb set up and fuel testing.

He has a dynojet. It would be great to get your #'s.


glad you made it. a new bike hey! impressive.

i'm chuffed that your _ _ P needle and 42PJ work so well. i hope to get everyone off the 48's and down to 42's if i can.

even the clip setting (2) is one of the lowest i've seen.

just one thing though, could you run a test for me please. could you try it for flat out (15T x 50T minimum gearing IMHO) and see how she picks up the last few revs. then go back to your 200 MAJ and see if it doesn't grab those last few revs quicker.

for full story read the latest in "jetting Q's".

appreciatte your analytical help here.


I am seriously looking at FMF's AOF ignition - ~$200.00 (I e-mailed them and asked if I'd be better off w/ the YZF's ignition vice the WR's w/ YZ timing - no response yet) and Eric Gorr's 420 kit in fix of my scored cylinder.

I then planned on having the bike dyno-jetted to end this misery of carb snafu's.

Then, I can sell it for a great loss and buy a CRF450 Honda grin.gif!

I will post all results...don't hold your breath...YET!


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat, Mobil 1 15W-50.


give me your complete jetting figures please. you shouldn't go on to your next set of goodies until you've got your last problems sorted.

as you know i have WR99. latest from me is 165 MJ (looking at 160 with the 160MAJ)

MAJ 180 (looking at 160/170)

EMM clip 2 (looking at 1 soon) (EKP 1)

PJ40 (looking at 38)

PAJ #85

PS 1.5

i've got the airbox lid off, white bros filter, PB header and europipe. the only difference i know of is that with your stroker tailpipe you would go to 170MJ.

i know that you have the CF airbox but beside that i should be able to get you close.

kev this thing is just flying. 15 x 48T. and flat out in 400 yards so let's get it right for you.

more than the figures try to describe where it's going wrong.


[This message has been edited by Taffy (edited October 08, 2001).]


I will try the 200 air jet in with it at WOT. I would like to try this on the dyno though so I can compare graphs.

While I have your attention let me run a theory by you and see what you think. My brother has a XR650L and just purchased a FCR 41mm from Sudco. He checked the float level and bolted it on. (170M,200MAJ,48 and 1.5 paj,EMR#3)It ran like s**t until it got on the main jet. He has it down to a 42 pilot and .5paj, #2 clip. Bike is running good but A/F mix screw is down to 1/4 before it makes a dent in the idle speed, and will still run ok when its off. We already know that the needle straight and pilot circuit overlap right? Theory: the PAJ only at .5 turn is richening the pilot circuit to compensate for a lean root dia. needle. The converse: My bike 42 and 1 to 1.5 PAJ to run well. PAJ leaning to compensate for a slightly rich root dia.,Altough I dont think a EMP is to rich based on what I have read. By the way this PJ/PAJ ratio seems to stay the same on both bikes when pilot jets were changed.(ie: mine 45/1.5-2.0; his 45/.5-.75) What do you think? Is the pilot circuit ratio showing if the needle is correct root dia.? We have thought about swappinng needles to test this.



I (think I) am running an FHP #5, 160MJ, 48 pilot,? turns on fuel screw, de-octopussed, DSP airbox REMOVED until jetting sorted out.

I put the YZ airjets into it when I removed the air-cut valve with whatever Clark recommended per his procedure.

I also had the AIRscrew in w/ the drilled out passage, but the bike was running so lean on top, it was virtually un-ridable. I put the stock YZ air jet back in temporarily to continue my ride w/ Bill in Pennsylvania back in June(?).

I am planning a flow test to correlate turns out on the airscrew compared to the (YZ) air jet that is installed to give me a starter baseline. I was actually planning on doing this today before I left for work...

I'll second check my jet specs in the morning, but I do think they are spot on.

Right now the top end acceleration isn't bad. Steady state throttle, upper mid range has the engine burbling momentarily BUT it is consistant. My bike seems to hit the rev limiter very early (~8K rpm). I have checked everything I can think of (neutral switch, TPS, swapped main jets - both leaner and richer, checked air filter, checked float height, checked YZ timing - verified by Bill, Mike68, Mike Carpenter, sealed up a header pipe to silencer leak, re-packed my Stroker SX-1, several new Splitfire and NGK plugs).

I have considered putting my stock pipe (minus the end cap) back on just for the heck of it for a comparison.

The cylinder does have some slight scoring in it from the water it ingested through the head vent back in '99 - hence the 420 kit.

I actually thought of dropping it off at Eric Gorr's speed shop in Wisconsin with a blank check!

I will tell you, the thought of a completely perfect carburated bike now has hit my ULTIMATE LIFELONG DREAM LIST. This is first with a close second of hitting the $50,000,000 lotto! grin.gif


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat, Mobil 1 15W-50.

Woody and Taffy,

Here are my latest results, EKQ needle, clip position 3, PA screw 1 3/4. Test ride at 4800 ft.

BTW Woody, you said you knew your bike needed carb tuning, why, what was the symptom? I never thought mine had any jetting issues until I tried the US pipe without the baffle. If it has a jetting deficiency, it might become more evident if I go to YZ timing.

Test 1, Euro pipe and all of the other stuff written below. Revs good and hits harder at the top. Just a hint harder to start. Occaisional backfire from WFO to closed

Test 2, Everything else same, Uncorked US pipe. Midrange stronger and as I previously had before changing the needle, sputtering when I try to hold constant RPM, but NOT as bad as before. Occaisional backfire from WFO to closed. Seems slightly starved for air.

Interestingly, Woody and I have the same riding conditions, but our mains are quite different. Do you think the 168 would help my constant rpm problem with the free flowing pipe?

Taffy, your setup is looking more like mine everyday. Anything you want me to try? I think you mentioned the clip earlier. Have you ever tried a free flowing pipe and had the rough running issue?

Also, just bought the stuff to do the BK, I will have it done this weekend.



01 WR426, uncorked stock pipe, EKQ POS#3, #158 Main.

[This message has been edited by Stefe9999 (edited October 08, 2001).]

[This message has been edited by Stefe9999 (edited October 08, 2001).]


After I uncorked the intake and exhaust I broke it in as per the manual then I took my maiden voyage! My first trip was to Texas Creek, CO on a twelve mile loop of mixed riding. (dirt road, loose rocky up and down hills, creek bed and embankment riding and finally 8" of slushy May snow at 9,000 ft) This riding really put the bike through the paces. I noticed the bike was bad blubbery between 1/8-1/2 throttle. That was my first indication it needed carb tuning. Back down @ 4600 ft I rode the bike the second time at an area called PMI. (near my home) I noticed it would misfire alot at steady speed, not popping and jerking, just missing a beat here and there. This was my second indication that carb tuning was in order. after I did the YZ timing and grey wire it cleared up a little bit but was still there. After my jetting the missing was worse but I started with a 45 pilot and 5/8 turn PAJ. As I leaned the pilot and increased the PAJ the missing went away.(I may try a 40 pilot, I ain't skeered!)

I am getting more anxious to try the dyno and at least get the main jet set. This will narrow down the speculating on which way to go w/main and MAJ combos. I think I may order the street tire this week. confused.gif

I wonder if with the US pipe being free flowing,is reversion an issue? I have found that 4" supertrapp discs are the correct size for the end of the muffler.(stock end cap removed) I need to make an adapter and do some dyno testing in the exhaust area as well.

By the way guys, I have access to maybe 40-50 take out dynojet main jets between 160-200 that are the same thread length and pitch as the MAJ. From the top of the threads to the top of the jet is a little longer but I think they will work. For a small shipping fee($5-$10?) I could ship you a handful to try.

Stefe what pilot jet do you have in?


[This message has been edited by Woody426 (edited October 08, 2001).]


It's good to hear that your carb tuning went well. I would also like to see the results with and without a main air jet.

On your brothers XR650 there needs to be some basis for how the settings should be approached. My suggestion is to keep the PAS at 1 turn (=#100) and pilot screw at 1 1/4 turn and find the pilot jet that works best. Then tweak the PAS (3/4-1 1/4 turns) or the pilot screw (1-2 turns) to find a best setting. If you're out of those ranges I think you have the wrong pilot jet, IMHO. An unresponsive idle is frequently too lean.

A factor in the differences observed could be slide cutaway. I have seen options for different slide numbers. Do you know what his and yours are?

The 650 has a bigger (41mm) standard Keihin version carb with different pilot jets and carb body. This may make them more difficult to compare. The most noteable thing about switching from a EMR to EMP on the same bike is that a richer clip position is needed with the leaner straight diameter of the EMR. (EMR#4 vs EMP#3) His 650 may need a leaner clip from the bigger displacement.


We have an dynojet 150 with some old software (still on windows 3.1) frown.gif

I'm working with my boss to try and get an EGA and update the system so we can better utilize our dyno, or at least so I can tune my WR better!

Please post your dyno results with some feedback on what was done. When I get mine i will do the same.


one reply at a time so;


your brothers bike seems to be very lean on the needle root _ _ R!! yug!

that will completely ruin the bottom end jetting (pilot system) all because of this. one is trying to bail the other out! i would try your 'P' in his and if you had an 'N' laying about even better.

while he's got that needle you've got the pilot system artificially rich for no other reason than to help the needle.

your needle could come down one more clip and he may even come down on the MJ.

one thing you and bro must get right is the PAJ and PJ ratio and you're both all over the show. for a 45 PJ one of you is on 65PAJ and the other on 140PAJ. i was on 1 turn @ #100. if this moves the problem elsewhere then look at the next problem.

i've found at present that if i've got the PAJ/PJ ratio right that turning the PS in doesn't kill the engine. one or two of patrick burns results are spot on and others are outside his experience i would suggest.

the only time my bike has 'died' when turning the PS in is when the PAJ was #100 the PJ was 42 and i went to 40 which upset the balance. when i turned the PS in it died.

i then dropped the PAJ mix from said #100 to #85 (5/8th of a turn) and all was hunky dorry again so turn down your PAJ a bit (tons!!)?

if you try the MAJ trick first and let me know i think that you'll be able to drop your MJ which on this carb leans it right down to 1/4 throttle.



now read your second post and 45PJ and 5/8th turn on you PAJ Screw is wrong. either get a 42 PJ or open the screw to around 1 turn.


we'll have to differ about the needle straight. if you go EMR to EMP you've juiced up the tickover and you can feel a slight difference for one yard. the needle clip shouldn't need to move. the needle is there for tickover and 3rd/4th gear roll on type stuff.


don't you mean the PS is 1 3/4 turns? your needle is two clips higher than mine but you've just opened your exhaust which will have a dramatic effect on your jetting. it's not a shudder, it's an earthquake!

unlike JD i've never sat down and written everyone's jetting down so i don't know your baseline jetting. if you give me that i'll have a crack at it as well.

Taffy (again!)

[This message has been edited by Taffy (edited October 09, 2001).]


i want more info please.

YZ or WR?

what year?


PAJ fitted?

what 'E' needles do you have on the shelf?

find out your PS?

YZ timing?

grey wire mod?

at the moment it sounds like the needle wants dropping at least one clip but i would rather you got it running as an E_ _ bike first.

you need patience! well ok, granted, i was pretty excited about my results in march but all the time i'm looking to do one change at a time.

i've got a drilled ET and needle combo waiting!

i've had a stroker tailpipe here only 6 months!

i've got a vortex ignition coming and DSP airbox as well but it will all have to wait while i get the PJ38 test, MAJ 160 test, needle down one more clip test.


so many women, so little time!



99 WR, YZ timed, grey wire cut, PAS NOT installed.

Needles on hand: EMN, EMP, EKP, DVP.

As I get my family out the door, I will be pulling my carb this morning to give you the rest.

I will modify this post as the info comes in.


that just leaves your PAJ size.

when you say that you have no PAS installed i hope you don't mean that. so let's be clear. when you look down the pillbox slit the jet on the RIGHT is the one you pulled out i hope. it was the MAJ and was a 200. i would put it back in.

the one on the left is the PA(Jet)Screw or (PAS) so what jet is installed or if it's the screw EXACTLY how many parts of a turn out is it.

finally what altitude. be patient, we'll get there.



My pilot is #42. Thanks for explaining, your bike does exactly what mine does with the US pipe. The EKQ improved on the problem, but did not cure it, so I'm still missing something.



Seems like every day I go back and forth with my pipe. You are right, my jetting gets thrown way off with the US pipe. So for now, I use the Euro, its quiet and the bike runs very well with it, constant revs and all, so I don't mind using it. Since we both use the pipe, I believe that is why you and I are having such good luck with similar jetting setups.

So, given that my jetting gets thrown off by the US pipe, what do you think would be the right thing to change in order to get smooth operation at constant rpm?

If we can fix this, I believe it will fix a lot of other people's problems on this site because I've heard the rough running complaint a lot. One thing we know, if it is the MJ Woody and I are both far from the right one because Woody has a 168 and I have a 158 and we both have the same problem!

Here is what I know about my jetting, EKQ-3, 158 main, 42 pilot, 1 3/4 turns PS, no air



Alright Taff,

- 99 WR

- YZ timed

- MAJ passage drilled out to 2.8mm (7/64"

for us yanks)

- MAJ drilled out to 2.3mm (#43 bit)

- 100 PAJ**

- FHP #5

- 160MJ

- 48 pilot

- 1.125 turns out on fuel screw

- de-octopussed

- DSP airbox REMOVED until jetting complete

- grey/gray wire cut

Needles on hand: EMN, EMP, EKP, DVP, FHP

**I DID have the Sudco airscrew installed,

but removed per previous post.

I ride at @ sea level (+ 277 meters out my basement door, then down the mountain to sea level)

Checking the accel pump, the fuel stream does not hit the slide at all, it goes straight into the throat of the carb. I am amazed at the quantity of fuel though!

BTW David, I have gone one tooth less on my countershaft (12 teeth?), rear is stock 52.


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, OEM YZ tank, IMS YZ seat, Mobil 1 15W-50.

[This message has been edited by NH Kevin (edited October 09, 2001).]


wow! your jetting is absolutely everywhere! sorry mate, but let's try and get it sorted.

go to EMN on clip 2 or 3


MAJ buy a #200, and if you feel wealthy #180

PAJ #100

PJ #42

PS? do snap tests at tickover for best but should be 1.5

the only difference between my bike and yours will be that i'm right down to;


PAJ #85

my needle (EMM)is on clip 2 (which is all i think you'll need)

quieter pipe runs MJ165 to your 175.

MAJ #180

APJ removed

remove the APJ. let's face it me and you (WR99er's)can't do the BK mod so we might as well have a go at this together hey!

lastly what i would say is that having needed a little extra on the MJ last weekend, i got a midrange boost! if you read patrick burns he says that the MJ works right down to zero and now i believe him (well, nearly!) so the old days of open pipe "ok, up one clip on the needle, 10 on the main jet" are gone. 10 on the MJ may well be enough with this carb).

this might not do it first time but it's only the pipe...

to dsconnect the APJ, undo the end nut on the black plastic pivot bar, pull the '7' bar out the hole. leave it there held only by the friction of the rubber boot.



Working right now, but able to squeeze in a few lines. I will have a street tire in my midst tomorrow. If what you are saying is true about the difference in MAJ/MJ between steph and I it will show up on the dyno running his jetting verses mine. (don't have a 158 though, will use a 160 or 155)Dyno runs should begin Thurs-Sat. this week.


I need some clarity on the post about needing to move the clip position on the EMP/EMR swap. My limited theory is this: a smaller root dia. will make the taper portion shorter because the angle of taper is a constant.(E-- = 1 degree taper) L1 (-M-) is the length of the needle from the bottom clip pos. to where the taper begins so this should be constant on both needles as well. The taper would therefore be shorter at the tip of the needle. This would be consistent with Taffy's opinion (no clip change needed.) But if the taper on the EMP needle(being shorter than the EMR)was shorter on the top portion(starting later)you would be correct JD. I hope this is making sense. Maybe you guys could further enlighten me, or just tell me I am full of sheet!



patrick burns has stated that the ET is crap on these and that what the dyno says and what is needed are different. this is particularly relevant to MJ which to get good Co # will be let's say a 158 but on the track you'll have to put a 168 in even though the dyno says it was dripping in fuel. that's because the ET cant mix it all up. so all the unburnt fuel makes the Co look silly.


when they make these needles they grind them down so that the distance from the top clip to the point that is 2.515mm dia is at a letter.

we're on about the middle letter ok? and presuming that we're grinding at the same angle of 1 Degree (E_ _).

so all you do is measure from the top clip a given distance to the letter 'A' and it's 2.515mm there.'B' is lower and 'C' is next. C and A can be identical by lifting the needle one clip. 'D' can equal 'B' by doing the same.

the straight dimension is done afterwards. so if we have a thin straight such as an 'M' (EKM)the grinder will make the start of taper move lower down the needle than say, a 'Q' needle (EKQ).

so the point of the needle isn't narrower when comparing the EMP/EMR. they are absolutely identical bar the thinness or thickness you might say of their straight.

so when we swop EMR for EMP we have dramatically altered the tickover. yes the taper will start higher by .5mm and fuel should start to pour up the side earlier.

SADLY THERE IS 6-8MM OF STRAIGHT NEEDLE stuck in the ET so do you think the earlier (.5mm) start makes a shyt's worth? nope!

but your tickover, ah well now we're talking.

JD's idea's are always valid and i overlook them at my peril.


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