James Dean - Needles what else


Have not heard from you for a while, have you done any more experimenting and come up with something needle wise that is more effective on the YZ timed bikes than a DVP or a EMN modified needle??



I have the EMM and EML on backorder from Sudco. They are the only close possibilities in a standard needle. I have also modified and made double taper needles with DVP and DTM as starting points. (No hasty decisions as to better choices) The modified EMN is still the hot setup to date.

EMP(EKP) works great if you can run it in clip #4-#5(#3-#4)and have a free flowing exhaust. YZ400/426 owners riding MX should take note of this needle choice. Also, when moving to leaner clip positions a richer pilot or modified needle helps reduce any hesitation near 1/4 throttle. At that point the EMN becomes a better alternative.

Can you tell me what drawbacks you have found with the DTM. Occasionally in the forum it appears the DTM is too rich and fouls plugs at low speeds or when riding long downhills. All the new KTM thump's are using this carb needle with a #48 pilot. Anyone else have a downside to the standard 98/99 WR needle DTM?? Altitude and warm temperatures?

Another question for you - Are the carbon fiber air boxes less restrictive at high speeds? For example are there extra openings or larger openings under the seat? There might be gains to using a more open airbox with larger main jet. Reason: Some of our members have found better acceleration with larger mains but not the good over-rev, just wondering if the airbox opening is a restricting factor.

James Dean


I feel the DTM needle is too rich on the straight section and still feel for hassel free jetting the DVP needle is the way to go with either WR or YZ timing (different clip positions WR vs YZ). I rode single track real technical stuff last weekend and went for the DVP vs the EMN because I wanted positive throttle control and no super hit.

In other situations I will run the EMN mod needle I currently have.

I'm on travel for work during the Moab ride week (I am Pissed) but will be riding two dual sport events in October (Dick Allens Ride in Mammuoth which I will finish and not in the ER and the Dual Dogs ride out of California Hot Springs--the last time any motorcycle will transverse these outstanding and scenic trails since the Clinton imposed National Monument will go into effect on Jan 1, 01----MAJOR &%$#@!**ING BUMMER.

So James I would like to send my modified EMN needle to you and let you use it and get a second opinion??? Is this ok??

As to the DSP CF air boxes I have both the completed CF box and the box only which uses the stock rubber boot. I cannot tell any performance difference between the two!!! But the forum members must realize I do not run motocross and if there is some tiny increase in the snap of the bike with the complete CF box that a Motocrosser may notice perhaps I'm missing it but seems remote to me. However, I'm still experiencing dirt getting into my Carby when I run the complete CF box and this does not happen with the CB box only using the stock rubber boot.

Both of these boxes are completely open across the top--much more open than a stock box with the snorkle removed.


[This message has been edited by Clark Mason (edited 09-21-2000).]

Hey Guys,

I am running the DSP airbox with velocity stack (DSP also). I am running a 180, 48, stock needle in position #4 I believe.

I have no problems with 1/4 response, not do I suffer any idel problems. I have ridden the bike as is in MX, SuperMotard and Trail riding. In all three cases, throttle response is smooth and equal through oput the range. I run 92 octane fuel. Although, I do suffer when altitude combines with cold temperature variations occur. I do not foul spark plugs due to this config. I am also running a Uni filter with DSP Pipe and Header.

If you like, I have a friend that could run the bike on a dyno for me and that way I can show you the smooth power delivery. In actual fact, the power feels equalised through the whole rev range.........



Thanks for the resposne, However, my observations are basied on a braod range of experience, helping people who have e-mailed me from numerous locations around the globe and I still feel that, in general the DTM needle is too rich on the straight section. Remember there is no one jetting solution which can handle "world wide conditions" each of us need a good starting point from which to establish our own jetting specs.

As to the DSP air box I stand by my observations that I cannnot tell any difference performance wise between the two DSP boxes (Complete Box vs Box only with the Stock rubber boot).



It would be great to try out your modified EMN. I will also graph it's profile as was done before. Let me know your other jetting settings (pilot/pilot screw/clip/main) and the temperature it was set for. This will give me a starting point.

Good inputs on the DTM and airbox from both. I may modify my airbox at some point as this has worked before for more topend.

The 1 degree E taper needles are a big jump from the 3/4 degree D taper needles and there are no off the shelf tapers in between. This only leaves shifting the clip and changing the straight diameter. 2.715mm straight diameter (M) appears to be borderline rich for some setups. EMM and EML will be interesting tests (richer) that may require smaller pilot jets.

This gets to the issue that Taffy keeps bringing up, decreased cutaway. If Taffy wants to prove his theory about the improved vaporization and throttle response, he could try this with an EKP needle and with a reduced cutaway. I think he already has one. This will be similar to a double taper between the standard D-- and E-- needles. It will be more effective than on a DVR where the taper is already very low. Basically it will match the EMN with the modified transition taper, richening the low end in a progressive manner and allowing clip #2-#3. This is standard practice for leaning out 2-stroke jetting, but it also works in reverse for richening the low end. Maybe Taffy can prove his point here, it's an excellent application in this situation. Well Taffy? It's your $$ this time, not mine... :)

James Dean :D


why is that spotlight beaming down on me!!!

as you know james i'm down at sea level with a standard DXM needle, 48 idle, white bros filter, airbox lid off, mix screw is 1 1/2 out, standard european exhaust (94db), 172 main jet (was 168). everything else is untouched.

my experience of playing with the carb is limited to trying the EKP needle @ #4 for 4 days on holiday.

so i'll stick to area's i've a good idea is the right direction.

the trouble is that i feel the bike carburates really well as it is. that slide cutaway is all about opening the throttle from dead. ie on the start line, up out of a ditch-that situation. whack & go instead of booooooooorrrrrrrr wang!!!!

clark, your bike is far more heavily modified than anyone else i've met in the forum. how can we replicate your experiments? look how standard mine is.

the more you modify, the more you chuck out yamaha's R & D budget & put in your own. time for a visit to the rolling road methinks.

but i must say i admire the countless hours you two have put into this.

clark, i hope you see the light & spend your money with a RR shop that has a hot carb specialist to help you.

now that's when you become a solid guy coz your going to spend your bucks but share the results. just like i will having forked out $180 for these variable cam sprockets.



can we make an appeal for an old slide complete or just the front plate that contains the slice cutaway arch at the bottom?

i know that one or two riders may have changed any/either of the above as a precaution against the cracks that were found in some 98 model slide's.

as long as they're sound right now they would make very good experimental parts. all that needs to be done is to have .5mm taken off the bottom & have one or two SMALLER pilot jets ready.

has anybody out there got an old slide or just the front face available that the wonderful members of this forum could experiment with to see if our theories might work?

we promise to tell all doncha know!!!


Yes Taffy,

Anyone have an old slide plate for an experiment on boosting low end? .... Not a cracked one by the way-- :)

The '98/'99 are different part numbers. See www.hlsm1.com (Yamaha/Dirt bikes) - '00 is the carb part #11 5JG-14546-00-00 and '98/'99 is #12 4FN-14546-01-00


Hang on... you want to try to cutaway .5 mm at the bottom of the carb slide? Wouldn't this let an excessive amount of air pass during all thottle positions? Wouldn't the amount of air be vastly different (higher) at small throttle openings, especially idle? Seems you need much larger pilots ready to counteract the increased fuel flow? Am I missing something here? And I would think the larger opening would make the airflow through the carb slower possibly decreasing atomization?

I'm no James or Clark, just making observations. Also I would think altering this importance piece may cause it to become weak and prone to failure (we all know what happens next!).

But then again you may be totally onto something. Probably no one has done this yet, could be the next "rev"olution.

My next jetting project will be measuring the exact amount of air filter oil to add every time when maintaining it. I know if I get a little too much on, it runs richer than I would like throwing off my overall observations. Anyone done this yet?

Good luck, taffy, let us know what you find!


you cut a slice across the bottom of the slide & that means that the little arch is now lower & therefore smaller OK?

mcarp i don't mind explaining this again but we really have been through this in minute (sp?)detail. please look at old posts.

this has been my pet subject for 6 MONTHS you must have been on holiday to lapland

what makes you think that having put the slide in clark, james or myself would run it one minute longer (lean?)like this than we had too?

this is a low speed circuit modification we're on about here, what kind of mechanical implosions were you thinking of?

sorry mcarp, but for me we're finally getting down to the nitty gritty. so hang on for the ride & LLL OK.


i haven't pulled the slide out recently-well only once anyway! so can you make a plate to go on the front-el cheapo. the other thing is; if you have screw holes & can slip the slide plate down .5mm by elongating the holes nothing else will have been touched (ie needle height, APJ ramp, WOT).



As Taffy said we are looking at reducing slide cutaway (the front side) by trimming the bottom of the plate (on the back side).


It doesn't look viable to shift the front/back elevations except by altering the plate. Does anyone know the difference between the '98/'99 carb slide plate and the '00 carb slide plate?? Have they been improved in any way?



i'm guessing here coz i'm not pulling the carb apart to have a look but the back plate & body of the slide dont need touching. it's just the front plate. either pull it off, machine it & put it back somehow lower & flush at the bottom OR can you pull the front plate off & have an exact copy made WITH the .5mm* (*see below) off therefore keeping your original plate free. you can soon measure the radius of the cutaway using the cup method.

either the footprint of a wine glass or a coffee mug will slip into the arc!!!!!

the 00 slide cutaway will be in the owners handbook-can someone check it out please!

i've been thinking about this cutaway experiment overnight & whereas my old duke had a 4.5mm cutaway & so .5mm was deemed OK i think that given that the cutaway is down as a "15"; if this is 1.5mm you should take off only .25mm as i'm going by the percentages. my 2 pence.

i'm sure that you know this JD; measure the cutaway by putting the slide on the kitchen table edge & put a vernier under the edge.

another one is to slide the shank end of drill pieces underneath until the next one doesn't fit!!

all good fun. ps the bike carburated 110% at the weekend & so i've been checking the valve timing to double check tonight. it's a bloody mess!!! (in my opinion)

anyway i've had the VTC slotted for checking adjustment & i should make an ass-i mean have a go this saturday.



There is no front plate, the slide body is the front -intake side. Look in your manual or at www.hlsm1.com . The back plate is the only option and it sits in a recess with no possibilty of shifting it's position relative to the slide.



i've beentold by a dickie-bird that there isn't another slide to choose from '15' is it.

can i ask you this. given that you want to juice the bike up at tickover with the PJ going from 45 (euro) to 48 or even 50 why did you choose the **P needle which is 2.735 & not go to say a **k which would have juiced things up @ 2.695?



(Note:EK- is the same as EM- shifted 1-clip)

I have tried EMM, EMN, EMP, EVQ, EMR (2.715, 2.725, 2.735, 2.745, 2.755). The EMJ was on backorder (2.705) and will be tested when it shows up. The EMJ is expected to be too rich based on the dull, rich feeling of the EMM. Feedback from Clark in the second posting here (above - DTM, 2.715) comfirms my view. An EMK (2.695) would have been well beyond the expected range. The EMP (EKP) is a mid-point setting that was not too rich or too lean. :D Clark's success with the DVP made me choose EMP first over the next richer EMN. Plus EMP (EKP) is already 2 steps richer than a stock 426 EKR.

The closer to a rich setting, the easier to cover lean hesitations. This makes the next richer EMN a possible option. The last thing I would want to do is give a recommendation that would cause plug fouling. :D The more I have used the EMN, the better it looks. But now the temperatures are cooler, 50-65F and the exhaust has a more restrictive spark arrestor.

The pilot jet dominates a slightly lower throttle setting than the needle straight diameter. They overlap some extent. The 48 pilot is the best choice in any configuration for my bike, my riding level and terrain. The pilot screw is usually at 1 turn out and a 100 air jet is better than 75. Note that ALL the KTM 400&520s are using this 48/100 combination. :)

My recommendations to use the EMP#4 (EKP#3_ should also have stated that if it hesitates, try a richer clip #4 or back out the pilot screw 1/4 turn. Beyond that an EMN is the next best choice.

Clark and I are still sharing some tricks with the jetting and needles. One of his modified EMN needles is in my bike now. :D This is an ongoing learning process that will last for many future bikes and hopefully help others.

James Dean

what i'm saying is 'how about weaning the bike off the APJ'. a bit like watching the last dry bit of your bath disappearing under the water, can you not start cutting it down & down? i'm thinking that all it should need is a bit of a squirt at around zero to 1/4 throttle.

i've really gone into the carb over the last two days, besides de-octopussing & fitting a needle that had been it! & i have to admit i should have looked at the slide. sorry for that, bit of an insult telling people what you think & you haven't even seen it! i never have seen that type of set-up before. my backplate on the slide is what i can hear rattling at tickover. no wonder the poor things break!

i'm really trying to get the hang of this m=n but move one clip etc etc. i'll get there. when i do i'll be onboard. i have the feeling you two have got a lovely little chart that makes it all so much clearer.

if you went to a thinner needle at the straight, could you lower the slide ready for that 'whack' (low slide & the whack, i feel go together) by going to a smaller pilot. for example a **L needle & a 42/45 idle with the slide height lowered & the tickover wound out to just 3-31/2 turns? would this help with this compromised needle you're (both) having problems (enjoying getting it sorted) with?

have you got those diaphram's yet. don't let the missus see them! she'll make you wear wellingtons!!!(you might not get that one!)

how do you recommend i delay the squirt on the 99 model JD?



[This message has been edited by Taffy (edited 10-17-2000).]


There isn't a problem from 0-1/4 throttle. The pilot and needle have it covered. Yes, yes, I have been backing off the APJ a little. Alot of low throttle operation can screw up the mixture if the APJ is quick and dumping too much fuel in going from 0-1/4 and back repetitively. If the pilot is lean and needle too (read this Hick), the accelerator pump can cover it. The throttle can be snapped open more quickly. Makes for an inconsistent mixture though, depends on your riding area if it matters.

Really need the squirt higher up at 1/4-full throttle. For pump delay just adjust the gap further open. On the'00 it is just 1/4 turn on the screw. The '99 has a forked gap in the linkage. Don't expect to change it too much though.

Will have to call on the diaphrams.

Wellingtons? didn't get it... :)


for my 2 pence i would get rid of the APJ as much as you can & only use it for the snapped throttle. hick riding a bike on a consistant throttle was a little extreme but nevertheless very relevant.

i would have said just a smidge off idle up to 1/2 throtttle at the maximum. if you can't get what you want with all that air flying in there by needle & MJ i'll be amazed. i'm sure you'll agree the bike is only set up like it is for emmisions-probably on a static throttle setting where the APJ has stopped working & everyone goes "look, it's running really lean!".

by having a really thin 'straight' on the needle i just wondered if this didn't help you with the rest of the needle profile.

Diaphram > dutch cap

dutch cap > condom

condom > "putting your boot on"

hope it goes well



A needle with more taper is more likely to work without the APJ.

Didn't get the diaphrams at the dealer yet. Wellingtons, got it...


[This message has been edited by James Dean (edited 10-17-2000).]

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