EMM vs DTM - WR vs YZ timing

Following is an excerpt of a thread that Taffy started called "DMM"


for those of you who DON'T want YZ timing and want that WR rattling stomp off the bottom i would recommend the DMM needle.

it could even be a better needle than the EMM that i recommend for YZ timing.

let me explain.

we all like that thin 'E' series needle. the bike gets more fuel and it goes like a rocket. so far so good.

after getting the jetting spot on though the 'D' needle doesn't appear to be the "blockage" it once was. the 'DMM' needle can be just as good and even better in wet grass etc where you want to do a 90d turn and not whizz into a 270d turn!!

the reason the DMM may be a better needle is because we have to set the needle for the midrange throttle. the second setting on the needle is the "straight". the one thing you can't dictate is when the taper starts. you're stuck with it.

take the point where a DMM and an EMM are the same diameter on the taper, now because the taper on the DMM is less it won't reach the start point for about another 3mm up the needle. i hope you follow.

this means that the DMM needle taper will start 3mm earlier than the EMM. this will help 0-1/8 and 0-1/4 throttle response and should make them wheelie monsters.

it needs someone who has the EMM needle to try the DMM back to back. a little low end work on jetting may be needed but it will be a question of which wins?

a gain in low end closed throttle snap and response versus any (if any) loss in midrange.

i hope someone will try it sometime.


web page


I am WR timed.

The stock needle on a '99 WR is a DTM. Isn't this the equivalent of a DMM except leaner because of clip position relative to beginning of taper.

Would a DMM or my DTM be a better fit than than the EMM. Any suggestions?

[ July 11, 2002: Message edited by: Littlefoot ]

[ July 11, 2002: Message edited by: Littlefoot ]

Before starting to jet out your bike, you should unkork it and remove the throttle stop.

My settings are : DTM (#5 or #6 forgot), MJ 170, BK mod , the rest is stock.

Works OK but still doesn't have the throttle response like if the engine was wired too your brain and wrist, I still have to adapt my riding style to the response of the bike, I would like it the other way.

Would like to try taffy's jetting, but it's difficult to find the jets and needles here. They only have OEM yamaha partnumbers, and no Keihin part n°s. :)

The throttle stop is cut and the exhaust is currently at the max dB level for my area. The air box snorkle is off but not the lid. See signature.

As I remember, back when most everyone ran 175 and up (MJ) someone reported loosing the MJ to vibration. No change in performance was noticed.

Others experimented and also found no change without the MJ in place.

Apparently the fat end of the D series needle restricted more flow than the MJ did, hence the thinner E series.

Now that Taff's jetting has the MJ requirement down significantly, it may be time to try the D needles again.

I have tried switching from my present DMM setup to a EMN. I should have had Sudco sent me a EMM also but at that time I ordered all they had was the dmm. My setup is 158mj 160maj 35pj 45paj dmm c1.

DMM runs very good low end. Great for picking you way through tight stuff. Front wheel comes up easy from just above idle. Revs quickly. Smooth linear acceleration. Really good for rocky tight stuff. Controllable power without alot of wheel spin. Just hooks up and goes. Doesn't have any big hits in the power band.

EMN same setup as above but clip on pos 4. Tried 3 and 5 but didn't run as well. Lost off idle ability to lift front wheel. Seemed to have more of a hit in acceration. I believe in a drag race that the DMM would win because it's already accelrating from the first turn of the throttle.

We all like the feeling when the surge of power hits but if that power translates to wheel spin all the horse power doesn't do any good if we can't put it to the ground. Wet dirt changes all of that. I live in So Cal and we are lucky to get any wet weather. So for me smoother power band works. Both Dmm and Emn felt like the same top end power.

Question for Taffy is

What difference is there between EMN and EMM?


i have to confess that if i could write that report again i would say "go get the DRM or find that ol' DTM boys!" putting a DMM on clip 1 isn't where it's at and obviously a DTM is the same needle but down 3 positions and a DRM down 2. all these needles are then identical.

to all

i'm chuffed that bman likes it and found what i said; to be true. good on ya!

you can still have a tractable rocket boys;

the PJ tests are good for the D series needles so a 35/45PAJ and Taff/BK mod will work well.

that MAJ test i can't be sure of because those of you who read jetting Qs will recall; the MAJ is there to alter the fuel curve and how it tails off. the tail off has to coincide with the power curve of the engine. DMM (DTM, DRM) have never been used for MAJ tests.

i'm pretty sure that #200MAJ is wrong for the WR but whether it's a #180 or a #160 or a #140 i can't be sure.

theoretically the drop off in power of the WR is bigger than the YZ. one could say that it peaks early and has a long downward taper. how much is carburettor and how much is cam and ignition only testing would tell.

your not running a "lean" jet to go to #150/#160MJ, you're running the right jet! and everyone else is rich. when i started here clark was pushing the #180MJ and now we're running #150's and happy. there is certainly no need for a 170+MJ's IMHO.

remember that a low MJ means a lifted needle, means the taper starts early, means more snap (as long as your PC hasn't been kicked out by this).

what you've all understood is this thing about the taper starting higher up the D needle compared to an E needle. and an early start as you pull the needle out to the taper is desired.

after all if you're opening the throttle to let air in at seems only fair that the needle should taper in and allow more fuel to party up.

our trouble was two years ago that we were running such high MJ's that the needles were dropped right down to stop the midrange "revlimiter/stutter". that meant that the tip was so fat that we weren't getting the midrange. E series was needed.

as i did my tests i started with the european DXM on clip 4 then 5, then 6, then 7, then 8! (work that one out!).

i stopped there and went to EMM and got on with life.

but as you will all appreciate i hope, the idea is that the next needle carries on the inward taper at the tip (so it's getting thinner) and the straight bit loses say, 5mm off the top and a load of new grooves are cut further down. i hope that makes sense. put it this way; ice cream cone, chop it off 1" from the bottom=the DXM. now put the 1" back on and chop 1" off the top. that's what happens when you go from DXM to DRM or even DMM.

so my DXM on clip 4 had gone to 8 (up 4!!!) the DMM on clip 3 is the equivelant of this. 5 clips different or if you like 5mm. (the DMM is on c1 because of the 160MAJ BTW folks).

that now means we're running much thinner D needles than 2 years ago. so thin that the advantage of the E series is getting smaller.

in the meantime the needle taper on the D starts 3mm sooner and thus bman's comments!

in the end i was lowering the E series (which makes it fatter in the midrange of course) and knew that the gap between the two was getting narrower. this lowering of the E series meant that we were no longer desperate for midrange fuel. it was getting all it needed.

thus in jetting Qs the comments that i will wait for the F needle, and wait... i finally commented that it couldn't be an improvement over the E to which JD agreed.

the ultimate needle will be a D series start and a touch of E near the end! a mixture.


[ May 17, 2002: Message edited by: Taffy ]

Here is the jetting I will now start with. (Well hopefully it'll start when i'm done with it).

I think I get it.

maj 160, mj 155, DTM C4, pa(j)s 45, pj 35, ps 1.5, sj 60, Taffy apj mod

I'll let you know what happens. Hope to get out this weekend although they are calling for rain.

To help clarify(or confuse) the needle relationships:


Littlefoot, you should compare the jetting you proposed with EMM#5/#150MJ (and otherwise the same) for the perspective of what they each can do for your bike.

My aussie model '99 WR4 (with airbox lid off) has a DXM needle standard. It rans s@#thouse in the midrange no matter which clip it's on! I'm trialing a DXL needle 2nite and will post results as soon as possible. Stay tuned! :)


be prepared to lift that needle if needed!

a DXL? yug!! richer on tickover on the richest tickover needle used on the site!



Originally posted by bman:

Question for Taffy is

What difference is there between EMN and EMM?

The latter will be one size richer on the straight diameter of the needle, the portion before the taper starts. So this affects very low throttle jetting in concert w/ the pilot jet.

Three letter code, first letter is taper, second is clip pos, last is straight diameter.

Interesting thread. For those trying different tapers you should, as was already mentioned above, be aware that you can't really change the needle taper independently, as this affects upper throttle jetting on the main as well.

I see DXL as the richest on "tickover" and leanest needle above that, considering it takes clip position #5-6 to get DXM in the typical range. What clip position would you run DXL in? #5?

Next we'll be running OBCVP!! I can just see it, add 30 to your main jet. :)

[ May 16, 2002: Message edited by: James Dean ]


In reply to your PM, you have the best advisors and the best advise you could possibly get. I have no further input at all. Your post brought out the very best responses of our very best experts.

Good luck,


Just makin sure it gets spread it around.


like the jetting. just thinking though. if you run an open pipe a 155MJ sounds good. but if you also run the D series needle you must go up again. i would suggest that a 158MJ or 160Mj will do. don't panic either will be about right.

for everyone else this is a guestimate but;

euro silencer and E series needle = 148MJ

open exhaust is worth +8

D series needle is worth +5

BUT the pair together IMHO = + 10



I wouldn't call it an open pipe. Here's the exhaust tip I have on a stock US WR pipe. I do still have my air box lid on, but the snorkle is removed.


I am currently 1999 400, WR timed, US WR pipe, but I have a modfied exhaust tip, removed the stock baffle, machined a cylinder of aluminum,(2.5 to 3 in long), to fit in it's place, then punched a hole in the aluminium to acccomodate a piece of 3/4 inch copper tubing about 7 in. long, kept drilling small holes, (3/16"), in the copper pipe portion that is inside the spark arrestor until walked up on the 94dB limit in Michigan.


I'm thinking maybe stay with the 155mj to start.

Whatcha think?

[ May 17, 2002: Message edited by: Littlefoot ]

Finally got some time to clean the carb and rejet. I went with the jetting in my signature. WOW :) what a difference! I didn't get to wring it out and do some real testing as far as high gear slight grade, etc., but here's what I experienced via seat of the pants:

Local conditions

55 degrees F., humidity high, low pressure

The hesitation I had from 0 throttle to 1/8th or a 1/4 is gone. This is going to help a lot in the tight stuff.

If I really wrap the throttle, instantaneously from closed to Full, I get a bog possibly a stall, if it doesn't stall, whamo the front tire's in the air, hold on!! Compared to before you have to be careful if you want the front tire to stay on the ground, this starts just off of idle. Exactly what I was looking for.

I did notice the bike seems to cool out faster, or, well it seems to like the choke more. Rode it, parked and talked for 1.5 hour, needed choke to start. When applying the choke I get a fast idle.

The bike will still run with the PS all the way in, but does appear to be in a lean surge condition.

I did pull my exhaust tip to see if anything would change, I just wanted to hear it, and the removal seemed to cause a loss of power. I had no popping on deceleration with or without the exhaust tip.

Almost forgot, I did install a fresh plug, NGK-CR8EIX, the new Iridium job.

I am very pleased with the difference. I bought this bike from a neighbor. He thought I was nuts to mess with such a "finnicky" carb. Good reason to mess with it if you ask me. I had him ride it. He couldn't believe the difference in peformance. I was showing him the APJ mod, by twisting the throttle and pointing out the APJ rod with now installed collar. He says, "don't touch the throttle you'll never get it started." There were no problems starting, it fired right up.

I plan on doing the high gear, slight grade, full throttle cut testing over memorial weekend. I want to lose the bog from the snap 0 to full throttle. When this is sorted out I'll try the EMM, EMN or one of their equivelants to see the difference.

What about that high idle when the choke is on?

Comments, suggestions?


Finally a place I can chime in. When you whack the throttle and it cuts out or coughs or dies, the problem is lack of fuel. Your accelerator pump is now doing too little for that condition. But what you've found is that the leaner (less pump) is so much more snappy without it until it gets into this cut out/cough/die condition.

You could play with it and determine whether it needs more fuel for a little while or some fuel for a longer while. The way to do this is to whack it on the stand, in 1st, 2nd, 3rd, etc. If on the stand (where the engine revs the fastest) it coughs or cuts out, you need more volume. If it doesn't do it until in 3rd or so at low RPM, you need longer duration (viagra?).

Unfortunately, on the '99 carb, you don't have many choices about duration. I'm not even sure if you have a timing screw (when the spray starts) on these carbs.

I like the snappiness so much, I would be willing to live with a little cutting out in higher gears instead of making all leading throttle sluggish.

The choke is supposed to increase RPM, as is the hot start.

In the last paragraph, you referred to 'lose the bog from the snap 0 to full throttle'. If itis a bog, not just cutting out quietly, coughing, or dying, ignore what I just said about the AP. The AP isn't likely involved in that. (BTW, I consider a bog a substantial decrease in power with a distinctive sound.)

Good luck,



you can't jet a bike on the stand. you make a mockery out of jetting.

if you can't catch the engine out on the track then you're ok. that's what matters.

i would go and do some snap wheelie tests and turn that fuel screw in and out etc. i get the feeling that it will need +.5 turn IMO. but go try it.

the whole choke thing i believe is in jetting Qs. go see.

i think it goes like this.

rich pilot circuit= choke is low revving

a little rich= revs it's nuts off

just right= revs dead steady from the off.


Guess I will print read and enjoy.

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