EMM vs DTM - WR vs YZ timing

just been and checked jetting Qs for my own sanity and benifit, i remember now!

basically if you have a M needle that's in clip 1, 2, 3 the M is fine for starting when warm. if you have it on clips 5, 6, 7 the needle ahs so little of the straight in the ET that an N would be ideal. anyone at altitude and i trust hick here should have an N needle and go to a P. me? at sea level in blighty the P needle was P (piss) what else!

to start the bike the choke makes it scream so you need to go to a lower "starter jet". i went from #62 to a #60.

it's all there from december 2nd onward littlefoot.


I was reading as you were. No printing toooo much paper. I'll just search.

Thanks again.

I'll post more results/observations after this weekend.




Needle-DTM c#4


PA(J) Screw-45




Environment, 70F, Low Humidity

Got to ride this weekend. Here are results:

Rode through Michigan woods, sand, uphills downhills, twisty turny stuff and clear cuts, whoops. Bike never bogged or cutout, Starting is excellent. 2 kicks after a 200 mile trailer ride, one kick after being warmed up.

Whack the throttle from idle or just above and will stall or cut out. Tried adjusting PS in and out could not get rid of this to just pop wheelies.

If running above idle and give alot of throttle but not really a whack to full, front wheel up.

On a road with an uphill grade, in 5th gear, if roll on to full throttle from slow speed (less than half throttle) engine cuts out, not a bog and would stall if I didn't let off.

Roll on throttle from half throttle or above no bog or cutout but seems flat at higher RPM's.

At topend of rpm's misses like up against the rev limiter, sure doesn't seem like the revs are high enough to hit the limiter.

The first day I jetted it seemed more responsive. You had to be careful to keep the frontend down.

That day it was 55F and humid.

well it's your needle but which way to go?

i would say that you're lean so raise it one and if this doesn't work then drop it. the answer is c3 or c5.

it may slightly alter the way it moves off in first gear etc so let us know.


1000 ft., 75F, High pressure

I went to clip #5 on the needle. It definitely helped the high load throttle roll on test. This was done on uphills in dirt, 3rd gear but it had a reasnoable load. Started to get a little burble and some boowaaa from 1/4 to 1/3 trhottle in this test. turned PS from 1 1/2 to 3/4 had very slight effect on this but took away some snap from 0 or just off 0 throttle. Still seems like it wants something up top to get the power on rev out.

My thoughts are put the PS back to 1 1/2, open the PAJ(S) to 1/2, maybe raise the needle another clip. I see Thronc is doing a parallel setup.

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

I have to say there are NO issues with starting either cold, hot, or after stalling.

This is great in the tight woods and sand.

Just for fun while riding with my Son I tried using 3rd gear and never shifting. Up, dowm, sand rock wash. I think I will have to add a John-Deer sticker.

Could be MAJ/MJ ratios, sounds like rich at high RPMS, lean under load.

You're a step or two ahead of me, but the top end really sounds like what I have.

I've got to say, that low end is incredible. I was testing on a dirt uphill ~ 30 degrees in second and third _just_ above idle. roll on and the front wheel was in the air.

RPMs were so low that looking back at the rear wheel you could see it slip on each power stroke.

I can't wait to get it all straight.

can you expect a lot more from the top end on WR timing?

i'm not so sure.

anyway. just for others my MJ guestimate goes like this.

my WR liked a 148/150MJ it had an;

E needle

a quiet pipe


you're below 2,000ft altitude so we're about the same IMHO.



D needle = +5-8

open pipe = + 5-8

same MAJ.

the two combined though would be about + 10-12

so a 148 could become a 165 tops. you could try a 162 MJ and see if that improves it.

i would definately try this first. drop the needle second back to c4.

finally you should unscrew the PAS to #60 as a third test.

i reckon you're close. but remember that YZ timing is 1/3 of a camsprocket tooth out where as thge WR is 2/3 of a tooth out. so the bike is never going to be spot on.



The DTM#5 is close to what many KTM riders are using to get the similar results- DMN#3 which equals DTN#6. A few have DMP#3 also.

The xxN is leaner than xxM at 0-1/4 throttle. This gives you more flexibility in the pilot jet and fuel screw settings and allows the richer clip position's too. They often lower the pilot jet with it.

You really need to get an EMM or EMN(or equivalent) to see what the other side has to offer here. The YZ426, YZ250F, and WR250F all run "Exx" needles. This adds fuel to the mid-range for that extended pull & wheelies. I won't guarantee that it will be better, just different. Some feel it has a more "wired to the brain" sensation at the throttle. If the top end has the wrong main it will feel flat(probably rich). As Taffy mentioned, the Dxx needle takes a bigger main than Exx by +5-8.

Interested in hearing where the options take you from here.



I have an EMM in my supplies, kind of chomping at the bit to give it a try, but I want to get the best out of the DXX needle for comparison.

The difference is enough that you should just drop it in for a quick test run. Clip position #5 (or #4) will give you some of that feel that DTM#6 has in the mid-range, but cleaner running down low.

The "Exx" needle is a standard taper from the carb manufacturer, Keihin. The Dxx is not, which makes the lean mid-throttle that you're trying to compensate for. There is only so much you can do to compensate for the imbalance of the D taper.

[ June 14, 2002: Message edited by: James Dean ]

In thinking about jetting with the DTM I find myself going back to the stock 168 main to get the mid range out of the needle. Maybe that's what Yamaha did, then used the 200 MAJ to lean out the top end.

I dropped in the EMM #4 and opened the PAJ-S to 1/2. I retained the 158MJ, 160MAJ, 35PJ, 60SJ, and .024APJ, 1 1/2PS.

When staring cold with choke I did not get as high of an idle, richer PC?

Went for a test ride around the neigborhood, shut her off and let sit for 5 to 10 minutes, I believe this actually helps to get warmed up as no air or coolant flow. Started it back up, had to use the hotstart, richer again? I have generally not needed the hotstart.

Rode around some, seemed richer just off idle. I would have thought with both needles being XXM that to 1/4 or so throttle they would be the same.

Maybe opening the PAJ-S to 1/2 from 1/4 actually richened the pilot cicuit as being set at 1/4 possibly cuts down on the air so much as to lean the PC. I haven't made a wide open or even 3/4 throttle run yet, so if the MJ is rich and I drop to say a 155 I think that would affect off idle/starting also, other thought, go to an EMN if the main is o.k. that should also lean out the off idle and starting.

souinds like a case of going to EMN (with emphasis on the N!). infact unlike most posts recently that have left me thinking &%$#@!, i'm 90% on this, so your hunch is probably correct.


Wnt back to DTM to try and smoothe out the power for woods riding.

Here is the problem.

Still showing sign of being lean on the PC. When throttle is closed quickly I get popping on deceleration. However the plug still reads light tan.

Open pipe=Procircuit T4 with Quiet core


MAJ=170-can try a 160

DTM #4


PAJ screw=60


airbox lid removed.

Where do I go from here to stop the popping on deceleration? Runs pretty good but not as snappy as my signature setting.

Originally posted by Mike from WA:

Where do I go from here to stop the popping on deceleration? Runs pretty good but not as snappy as my signature setting.

You went leaner on the pilot 45 to 40, a big change (but richer on straight from N to M). I run a 40 pilot and about 85 PAJ w/ stock YZ exhaust so 60 seems small/rich.

What rpm is the popping at its worst? Lower rpm popping needs some combination of idle (and possibly straight diameter?) and pilot…

I used to have a T4 on my bike and I learned to live with a small amount of decel popping. Going smaller on the PAJ didn’t stop it completely, sort of a diminishing returns thing, I could richen up the idle mix and get rid of it completely but this killed starting and response. The popping I was “living” with was very slight and at lower rpms…

The change that sticks out to me is the 45 to 40 pilot. I don’t know how you arrived at the 40 pilot, but if it were me I would try a 42 and try 80 to 100 on the PAJ afterwards to get the high-rpm popping under control.

I’m assuming you have already dialed in the idle mix, but maybe a ¼ to half turn out there will make you happy.

[ June 20, 2002: Message edited by: Hick ]

Oops. Hit the wrong button again :)

[ June 20, 2002: Message edited by: Hick ]


i just didn't used to go by the decel popping. i had it very mildly when i finally went below 40PJ. but it's no big deal. don't panic.

you should be checking waht everything does on the way up and not the way down.


i would lift the needle a clip. otherwise you've got to experiment for yourself. as has been said before, you've cut dozens of hours of work out and now to fine tune it you must do a little experimenting for yourself.

things like "how long on choke" etc help.




0-1000 feet

humidity high

Rode 4 hours this past weekend, terrain varied from very tight woods to deep sand hills, rock wash climbs, some fire roading, lots of up and down hills in woods. The 400 just ran awsome not one stumble or bog anywhere. Fell over one time on a rock wash climb, wasn't paying attention kind of lolly gagging and got caught up in the wrong gear, any way, picked her back up, started one kick, I just love that. This bike starts sooo easy now, and performance is awesome.

The changes I made are:


PAJ(S)1/2>1/4 (this leaned the pilot circuit)

PS 3/4>1

The EMM did not create a HIT in the mid range, it just eliminated the leanness of the midrange. I would guess the combo of YZ or Taffy's cam timing and another clip higher, (richer), on the needle could cause the hit.

The PAJ(S) from 1/2 to 1/4 leaning the PC and providing better starting and off idle performance leads me to believe the needle root diameter is indeed too small in my application and I have order the OBEKN from Yamaha.

Here's how it ended up and for right now I'm satisfied. Easy starting, awesome performance.

When I get the EKN I will repost.

'99 WR400



Needle-EMM c#4


PA(J) Screw-45 (1/4 turn out)




WR timing

throttle stop cut

semi uncorked, (snorkel off/stock pipe with custom exhaust tip)

grey wire pulled


[ June 24, 2002: Message edited by: Littlefoot ]

[ June 24, 2002: Message edited by: Littlefoot ]

ok, so i got my emm needle, 160 mj and 160maj, i also got the 35 slow jet,. the 45 paj nevber came and the order was cansuled. what pj can i run with this set up and the stock paj. my bike is a 2000 wr400, yz, timed , full wb system, lid off. also where should i put the clip.


i can't see how you can be prepared to get involved in all this if you aren't prepared to buy the right gear?

you can buy 3 or 4 PAJ's but apparently it only takes two for this route to be more expensive than buying the PAS. get a #50 if you insist but don't say that we never told you so.

anyone would think that this was an exact science when it should be obvious to anyone that it's anything but...

keep it going littlefoot and let us know.


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