EKP or EMP or "E**" Series Needles

Any of you forum users trying these needles and if yes what are your results???

What jetting are you running with the needle?? Make year and model of bike? Any significant mods air box, porting, pipe, etc.

PJ =

Fuel Screw =

Needle and clip location

MJ =

Riding altitude and observations. Any hesitation or flat spots while realy wacking it in second or third gear??

I would like any feedback either positive or negative based on the experience of the FORUM users.




I tried the EMP series yesterday with the following:

170 main

48 pilot

4th clip EMP

2 turns out on the fuel screw

99 WR, YZ timing, stock WR pipe baffle out, airbox cover off, and white bros filter

Rode behind Lake Arrowhead/Silverwood - elevation 3 to 6k ?

Results - way way rich on transition to the needle (1/4 throttle). Felt like I was riding an XR it was so unresponsive. It was so bad at the end of the day - as the air filter got dirty - that I had to run with the hot start open.

Going to try a 45 pilot and a 168 or 165 main. If these don't work I may just go the DVP.

I saw a previous post where you observed the same thing. Have you solved it yet?

FYI - I forgot to mention that I have already tried dropping the needle one position (to the 3rd position) and it ran way too lean.


I tried EKP with the following jetting and results.

Trial #1 Altitude 1200 to 3000ft

EKP #3 from the top

50 PJ

Fuel screw at 1.0

172 Main jet

Way rich in transition onto the main would pull through it in 1st and 2nd but would bog in third gear. It was a stumbling fool

Trial #2

Same route and altitude

EKP #1

50 PJ

Fuel Screw 1.0

170 MJ

Performacne was improved almost acceptable no more stumbling but not as snappy as I would like.

Trial #3

EKP #2 from top


Fuel screw 2.0

168 Main jet

Things are staring to work better and performance was acceptable.

The route I take is about 54 miles and varies in altitude fron 1200 to 3000ft. I always use this route when comparing jetting.

I feel that the needle needs to come onto the main jet a little later in the throttle resonse and would imagin a true EPP, ESP or EVP (as read off the side of the needle) would work better in my bike. These needles should start the taper later in the throttle opening and the engine should be spooled up enough to take it. Im also toying with the idea that since the needle taper is more radical that the MAIN and PILOT jets will have more of an influence on things and more experimenting is warranted. I have been trying to get in touch with James Dean but so far no luck. I sure he will have some valuable insight into whats happening. If I canot get it dialed within a few weeks I will go back to the trusty DVP.


Thanks for the reply Clark. I'm about to put the carb back in the bike and maybe I'll try raising the clip 1 position again. I'll let you know the results when I get a chance to test it.

Sorry for the late response, been out camping...

Clark and Wilbot,

Thanks for the feedback. The 2 settings I have for comparison are:

'99WR -

EMN #4 from top (=EKN #3 from top)


Fuel screw 2 1/4

168 Main jet

75 deg F, 3-6000 ft elev

YZ timing, FMF PCIV2, air box cover off


'00WR -

EMP #4 from top (=EKP #3 from top)


Fuel screw 3/4

170 Main jet

75 deg F, 3-6000ft elev

YZ timing, YZ silencer, air box cover off


-Both of these are more lean down on the pilot jet/pilot screw. It appears this is the direction Clark is going down low.

-They also have free flowing exhausts (I suspect the FMF is). The YZ timing can be sensitive to exhaust restrictions when it comes to jetting from what I've seen. Any restriction will need leaner jetting. What temperatures are you riding in at your locations? It looks like both of you will end up 1-2 clips leaner and need smaller main jets. The YZ426 came stock with a #162(rev.-thanks ricky). This needle taper requires the main jet to be smaller as you are finding.

-Wilbot, What needle and clip were you using before? If 4th clip was way rich at 1/4 throttle, where was 3rd clip way too lean?? 1/8 - 1/4?

-As far as the needle options here, EMP and EVP are several clips leaner and could be used. EKP#2 equals EMP#3 and EVP#7. Nothing is available between them. (The middle letter is clip to taper start distance)

-If the low end richness is a problem at high altitudes and warm temperatures, try the stock YZ426 EKR (EMR).

James Dean

[This message has been edited by James Dean (edited 07-31-2000).]

James & Clark:

Thanks for the response James. Yesterday I replaced the EMP needle with the (backordered) EKP that I finally received (even though it shouldn’t make a difference) and ran the following:

45 pilot

2 turns out

2nd clip position

168 main (this is the smallest that I had available but I am planning on trying a 165 and/or a 162)

I ran a quick test at ~1500 feet and the temp was about 85-90

This setup worked much better but there’s a small lag when I whack the throttle and I think it’s still too rich on the main.

James - It seems strange to me as well that the EMP could be too rich at the 4th position and too lean at the 3rd. It felt lean at the 3rd clip where you said – at about 1/8 to 1/4 throttle. One other variable was changed between the two tests: the TPS was returned from full clockwise to within factory specs (closed throttle resistance of 0.15 x TPS resistance) – don’t know what effect this would have on jetting. The temperature on my ride Sunday (needle in the 4th clip position) was about 90 degrees.

Clark – I have not tried the DVP and was wondering how the EKP and DVP setups compare?


The TPS is an unknown factor. Could the lag be from the TPS??? Were you using the stock DTM before in clip #3?

The smaller main will solve the top end richness and this may be associated with your problem with clip #4 being too rich. The small lag might be helped with backing out the pilot screw 1/4 turn or tweaking the TPS. The EKP is a little leaner than the DTM which might have made a difference down low. Notice the '99WR example above used EMN#4 (EKN#3) which is closer to the stock jetting at 0-1/4 throttle(last letters M,N,P). The '00WR uses a richer pilot jet. Your settings are very close to both the examples, but each are a little richer down low. If the lag persists, consider either pilot #48 or revisiting EKP clip #3 with a smaller main - 162.



Has anybody tried to adjust the accel. pump?

I finally did and my 426 now rips everywhere whithout hesitation.

Thanks to Ando, who told me to look for slop/slack in the accel. pump linkage.

When you look at the cam (black plastic thing that pushes the accel. plunger) you can see that it does not contact the plunger immediatly when the throttle is opened. I turned the adjust screw CCW 3/4 turn, which took most but not all play out.(did not want to get "radical"). What a HUGE improvement!

Full throttle acceleration through 5th gear without a miss!

Stats: YZ426, approx 1500 miles, Big Gun SDS, pilot jet #42, fuel screw 1 1/8, needle (stock) clip #2 from top, main #158.

BTW stock main is #162, not 165, checked my manual and jet.

I rode about 10 hrs Fri-Sun, from 5500ft to 8500ft, (I live at 6500ft) and the bike was awsome!

This is the first and only experience at carb tuning, it was totally seat of the pants, but it sure runs great.

I would welcome anyone who "knows their stuff" to ride my 426 for an evaluation.

P.S. Thanks to all who have helped me learn so much.


Rick Fuller

'00 YZ426

'81 490 Maico


What was the temperature on this ride?

The '99WR accelerator pump is much different to adjust.

Your jetting is noted as:

EKR #2 from top (=EMR #3 from top)

#42 PJ

Fuel screw 1 1/8

#158 main


Looks like smaller main jets should be considered... (range thus far is 158-172)



James, the temp was 75-80 deg. What main jet do you suggest?


Rick Fuller

'00 YZ426

'81 490 Maico


Thanks - your recommendations make sense. I have not used the DTM needle since I changed to YZ timing. All YZ timing tests/rides save the very last one were done with the EMP. I did use the DTM with WR timing and it worked well at the stock, 3rd position and now that I think about it, it makes sense that with the new needle I should bump up the pilot.

And now ricky1 throws in another variable! Thanks for the info on the accel pump.

BTW does anyone know what rotating the TPS does? I believe that it advances the ignition curve but do not know how this effects jetting. I rotated it back since, when rotated clockwise the resistance at closed throttle was ~1.1 k ohms and the total TPS resistance was only ~4.3 k (still within the factory specs of 4 to 6). This puts me outside factory specs for closed throttle resistance by quite a bit (1.1/4.3 = 0.26 and specs are 0.13 to 0.15 x TPS resistance). If, however, the TPS ohmed out at 6 k then I would be near the upper limit of the specs for closed throttle resistance (1.1/6 = 0.18). So I’m not sure that the suggestion to rotate it fully clockwise should be universal. It seems that the degree of rotation should depend on the TPS resistance. I hesitate to mess with it since, from what I understand, excessive advancing of the ignition curve can damage the engine.

Maybe I’m thinking about it too much and need to just ride.


I know what you're saying about the TPS tolerance...(4 to 6)*(.13-.15)=.52 to .90 >> and agree about the last part. Probably not worth messing with the TPS much, just ride :)



I have a small track on the 5 acres around my house to test and don't have enough wide open space to adequately check main jet sizes. Temp, altitude, setup, etc. would make it difficult to encompass it all anyway. Just trying to give a range which looks to be lower than first thought, probably #158-172.


James, I guess it is time for me to do a plug check. I think I read that one should start with the pilot circut and work from there, and that is what I have done. I started with the fuel screw, then the pilot jet and needle, all by feel. I went from a 162 to 158 main on the advice of Paul from Big Gun. Can't say I noticed a difference with the leaner main, but I was mainly trying to get rid of the low speed stumbling.

The two steps leaner on the needle made it better, but the accel. pump adjustment was the coup de gras.


As requested in my e-mail to you what are the available needles and where can I get them.

I'm interested in a later taper activation as in a EVP / ETP vs EKP. I fully understand the needle codes and their implications. I'm positive I will develop a custom taper over the next few months. So James whats available in the later taper and from whom??



see James D. EKP Needle + Options posting. I also sent an e-mail from work about adding tapers/ where to and how much, did you get it?

[This message has been edited by James Dean (edited 07-31-2000).]


Got the e-mail thanks for the info. I will be doing a little experimenting of my own and most probablile will creat a custom taper from the EVP or maybe and maybe a multi taper from a "F**" needle. But it will require time and I have little to didicate at the moment. James I know you are working along similar lines if you get a good responding multitaper needle make two and I will purchase one plus you labor if the rate is reaonable, I have super commitments at work currently.

James thanks for the source information


500 to 1500feet...

Stock WR needle, 4th clip

180 Main

48 Pilot

2 to 2.25 turns out

YZ timing

DSP Pipe

DSP Airbox + Velocity Stack

At these altitudes and on not too cold a day... (anything below 15 degrees celcius) the bike runs great.....

Temp goes below 15 and she runs really rough. Mid throttle performance results in hesitation.

Altitudes above 2000 feet, SHITE... Mid id severely effected.

I am getting some feedback from the DSP distributors and will update you in a few days.



If you are YZ cam timed I would be running a DVP needle in the #4 from the top position or a DVR in the #5. DVP works a little better. Yam Part number 5BE-14916-DP. I am experimenting with James Dean's EKP needle in my WZ 420 but have not got it sorted out yet getting close more to follow.


Ok Clark,

Will see if more improvement can be had with double and triple taper needles. The 2-strokes have taken years to get their carbs dialed with these and sometimes it seems like they use a dartboard approach. Careful tweaking yields gains without tradeoffs from my humble perspective. :)


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