JD Jetting needles worth it?

7 replies to this topic
  • RockerYZWR

Posted January 10, 2014 - 09:18 AM


I posed this question in the "What did you do to your WR today" thread, but I wanted to get some opinions before I return the JD Jetting kit I've got to RMATV today at lunch.


I've got my carb set up pretty darn well right now - it starts/runs great in the summer and after throwing in the 170 main and tweaking the fuel screw, it starts/runs great in the winter also.

Straight from the other thread: I'm at about 4000' MSL and the temps when I ride right now are around 50 deg F.  My current set up is:


Main: 170

Pilot: 48 (I think...I just pulled it to check when I re-jetted and wrote it down at home)

Leak: 45 (and I have my accelerator pump linkage safety wired together)

PAJ: stock

Starter: stock

Fuel screw: 1.75 or 2 turns, I forget (tweaked it with the tachometer)

Needle: GYTR, third groove from the top


So my real question is: are the JD needles really worth holding onto this jet kit?  I didn't realize how many extra jets and parts I had laying around when I ordered it, and all I could use would be their red and blue needles.  Not to mention I was pretty underwhelmed with what you get for $75.  The GYTR needle as set seems to do great and I have no dead spots anywhere.  This would seem to answer my question, but just curious if anyone thinks the JD needles are magic and would be worth trying for $75.


  • grayracer513

Posted January 10, 2014 - 09:42 AM


The stock WR needle on later models can't be adjusted up or down, and often is not the optimum profile.  That being said, the question is whether to use the JD or another OEM Keihin needle.  The only thing in the JD's favor is that somebody ostensibly has done the research and trial and error part for you so you don't have to guess at which of the "real" Keihin needles is the best choice.  The WR, as you probably already know, has the additional complication of the air cut valve, which changes the layout of the pilot air circuit considerably, and that can spill over into the operating zone that the needle meters.  Doesn't necessarily work to simply take a YZ needle and toss it in.


If you can get a reliable recommendation on at least a good staring point, using OEM needles is quite a bit cheaper.  Personally, the couple of times I've tried jet kit needles, I have not been content with the outcome.  The needle offered through GYT-R may actually be a JD, or it may not, but having Yamaha's endorsement would draw me to it, and if it works, well...

  • RockerYZWR

Posted January 10, 2014 - 10:10 AM


Thanks a lot for the quick response.


I currently use the GYTR needle that has seven different clip grooves and at third from the top, everything really seems to be just fine - I haven't changed that setting and tried different needle postions with the temperature change - just went with a larger main jet for the cold weather.  But holding the GYTR needle side by side with both the red and blue JD needles, I just cannot break out any appreciable difference visually between them.  I know the taper and profile differences are very slight in how much and when fuel is metered through the needle jet, but for the money, I can't imagine the likely small difference the JD needles would create would really be noticeable to me and worth $75.  Just curious if anyone who's tried both really swears by the JD needles.  And you're right - if it works...


I'm gonna send the kit back today.  Thanks again for the reply.

  • grayracer513

Posted January 10, 2014 - 10:18 AM


The things to look at when comparing needles visually are:


The overall length (pretty much has to be the same or the two won't interchange)


The diameter of the upper, straight part (affects mixture from off idle to around 1/4, where the taper begins to rise out of the main nozzle)


The length from the start of the taper to the top, or to any particular clip groove


The diameter of the small end


Whether the taper is "single" (one constant taper down the length), compound (2 or more tapering rates), or curved.  Both the last types of taper are quite rare.

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  • beezer

Posted January 10, 2014 - 10:19 AM


I use an NCVQ at #4.  Had good luck with that.


I've tried JD needles and wasn't thrilled with the results.


Yamaha needles are like 12 bucks.


I always use an adjustable leak jet and fuel screw.


It made dialing the bike in very easy.

  • RMK800

Posted January 10, 2014 - 11:37 AM


I really like this needle. Kranie backs it up also.

http://www.thumperta...tter then stock

  • Krannie McKranface

Posted January 10, 2014 - 05:40 PM


 Literally every one here could actually use a different needle......if we all had simple ways of determining stoichiometric balance of fuel/air ratio.





....but we (at least not me)   don't have the equipment to find this ratio at all rpms.


It's actually not that difficult: rpm gauge and a bung welded into your header to insert a F/A ratio meter....which aren't even all that expensive.

Then lots of time mapping rpm vs F/A ratio, and figuring it out. 



So, we 'copy' someone else's 'known' jetting that seems to work well for them, hoping it will work well for us.


I like the NCVS for the uncorked Hondas and WR's. Works as well as I have experienced. I found the JD needle to be too rich, at all settings.

Could it be better? I'll probably never know.

Edited by TheKoolAidMadeMeSick, January 10, 2014 - 05:41 PM.

  • beezer

Posted January 11, 2014 - 05:31 AM


I should try the NCVS.


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