Jetting FAQs

With the N3EJ, you'd start with the 2nd clip as a baseline.
It's a little bit shorter needle. It has a larger root diameter than yours, which makes it anywhere from 3-10% leaner between 0 and 1/8th throttle (you are probably going to have to go up one on the pilot with this needle). It's 10% richer at 1/4 throttle, but since it has a steeper taper, it's only 4% richer at 3/4 throttle.

I'd stay with the same main jet.  
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Duh, I need a 420 main in the winter. Thanks for figuring that out for me Skip. I swear to god, the TMX-x needs rejetting for every 5deg change in temp.  
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Even a broken clock is right twice a day.

Smartazz..

My CRF150RB is the same way - if I wear warmer clothes, I need to rejet it.  
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Skip I saw a N3EJ-3 whats the difference??

I called my local dealer and he said he couldn't find one. Is it a sudco part??  

ML - your dealer is an idiot.  N3EJ-3 is simply the N3EJ needle in the 3rd clip position (hence the -3), now back to the idiot... N3EJ is on the Yamaha OEM microfiche as an alternate needle for all 2002-2009 YZ250's, but since he's too lazy to even look at the microfiche, just tell him you need a stock needle for a 2005 YZ250 and you'll be getting the N3EJ.  
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Skipper:
ML - your dealer is an idiot.  N3EJ-3 is simply the N3EJ needle in the 3rd clip position (hence the -3), now back to the idiot... N3EJ is on the Yamaha OEM microfiche as an alternate needle for all 2002-2009 YZ250's, but since he's too lazy to even look at the microfiche, just tell him you need a stock needle for a 2005 YZ250 and you'll be getting the N3EJ.

i thought he was a little sluggish. I googles the number and saw a bunch of post for it use in other bikes like KTM's.


do u use the step washers much?  

Those washers are GREAT for fine-tuning a needle..!  I got a bag of 12, I think, for like $10 from Sudco.  I freqently find that a whole clip position is too much, and using a shim is much cheaper than buying a 1/2 clip longer needle.. well worth it!  
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i really seems so finite?? its hard for me to fathom  the difference in half a step.

when there are so many other factors that have to go correctly before the needle even comes into play.

temp
elevation
mixture
density of air cleaner oil
quality of fuel
compression
jetting including air screw
cutaway
reeds
exhaust
any engine mods-like porting or changing the squish
condition of electrical components
condition of spark plug

all of this crap has to work in sync in a pilot circuit to deliver a crisp signal before the transition into the needle and on to the next stage of the main circuit  

when you get to the nth degree of fine tuning, and I mean dialed in to perfection, a half clip can make a noticable difference!  The smaller the needle, the bigger the difference you can feel from it.  
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Skipper:
when you get to the nth degree of fine tuning, and I mean dialed in to perfection, a half clip can make a noticable difference!  The smaller the needle, the bigger the difference you can feel from it.

Don't u think that just the difference in fuel quality is enough to give performance changes?? i,m saying in 1 tank full. Do u think that todays fuel lacks the consistency
to be efficient enough to notice subtle changes in jetting??

I can see running a quality race fuel, but running pump gas must deliver way too many ghost issues.  

I know it doesn't sound like much... but a 1/2 clip position accounts for a 5% AFR difference at 1/8th throttle, tapering to 3% at 3/4 throttle (on a yz250).  That's a bigger difference at 1/8th throttle than what you get with using the next size larger slide cutaway!

I can feel the difference very easily - even on pump gas.  Is it going to change HP much?  No.  But that 1/2 clip can mean the difference between a soft throttle and a snappy one, all other jetting being correct.

Let's put this another way - the difference between the red needle and the blue one in a JDJetting kit is typically half a clip.  You can easily feel the difference between those two needles  
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good post!
stick it to the jetting ape  
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1998 cr125
its better to own nothing worldly and still have your identity
then have the world and no identity
---------------------------------------"We were born of the night. We live in it. We will die in it. But tomorrow there will be light, for those now crying in the night. For those to whom day is denied. To whom death is a gift. To whom life is forbidden."

Skip They wen't from the N3EJ in 07 to the N3EW, Wouldnt it benefit his bike as well? It helped my 06 when i pulled out the N3EJ and put it in. Skip????  
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DIABETES SUX!

Skip????  
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DIABETES SUX!

Wood-meister!

The 98 YZ has a bit different port timing than the later YZ250's.. the N3EW is slightly richer at the root, and that would make his off-idle soft spot even softer.. hence the recommendation for the N3EJ.  
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