JD Kit Questions

[mark794]

Ive got a question about the JD Jetting Kit I just bought. I'm riding mostly mountain trails in So. Cal altitude 4-6 thousand feet. Using Pro Circuit exaust.

i had a low range sputter which I'm pretty confident I'm going to be cured

of due to excessive accelerator pump duration. (Just did the BK Mod...not tested at altitude yet) But it looks like it will work well. Still running the stock Pilot jet by the way.

My problem is that I was running a 160 main jet and was still burning a Fat plug before. Now i'm getting ready to put in the JD kit and it says to use a 170 main and the blue needle. I'm not a pro carb tuner but everything i'm seeing is telling me this will just make things worse. I'm tempted to run the red needle with the same jets but would like to hear pros/cons if anyone has had a simular problem.

[RogerDedrick]

Ive got a question about the JD Jetting Kit I just bought. I'm riding mostly mountain trails in So. Cal altitude 4-6 thousand feet. Using Pro Circuit exaust.

i had a low range sputter which I'm pretty confident I'm going to be cured

of due to excessive accelerator pump duration. (Just did the BK Mod...not tested at altitude yet) But it looks like it will work well. Still running the stock Pilot jet by the way.

My problem is that I was running a 160 main jet and was still burning a Fat plug before. Now i'm getting ready to put in the JD kit and it says to use a 170 main and the blue needle. I'm not a pro carb tuner but everything i'm seeing is telling me this will just make things worse. I'm tempted to run the red needle with the same jets but would like to hear pros/cons if anyone has had a simular problem.

The JD needle is a little larger in diameter. I think the 170 is better suited for sea level. I ride around 1-2000ft and was happy with the 168. According to the calculator you will want to go smaller than that at 6000ft. try the jetting forum and ask JD. He seems very helpfull.

[kincade]

Roger, what calculator are you talking about?

[Shuffler]

ditto for me on the JD kit. My bike ran great but recently started fouling plugs with a 158 main, so I got the JD kit for my '02 WR426 (same carb as the YZ). They say for altitude of 5k-10k + I should be running the 165 main. Seems like that'd be too rich, and comparing his needle vs. stock I couldn't really tell any difference...

I guess I'll just plan on fiddling with the main, the fuel screw (got a ZipTy) and find the right combo through trial and error. Seems like a lot of local TTers are running mains in the 152-162 range, so I'll start at 158 and see how it goes....

[Shuffler]

this is what JD emailed back to me a few days ago:

"The kit has instructions for both bikes above 6000ft up to 12000ft.

The red marked needle will work best in the middle (or maybe 3rd from top) position at higher altitude. The main jet should be a #165 until near 12000ft, then a #160 would be better. The stock #42 pilot jet is a good choice with fuel screw near 1 1/4 turns out from seated."

I just want to find the best main with the most flexibility so I don't have to change it out...

[RogerDedrick]

There is a spreadsheet floating around thumpertalk somewhere. I did not find it when I went looking for it at first but did find the math and as I was taking a Java programing class I did this program quickly for myself.

http://www.lightlink.com/rogerd/jet.html

I have since found the spreadsheet which is better as it creates a chart with many possible settings. you still need to find the base line setting for your bike with its combination of exhaust etc. With the spreadsheet you can print that out and put a copy in your toolbox.I am sure that I have a copy of that sheet probably on my shop computer. Let me know if you can not find it.

[mark794]

I've decided to run the blue needle (4th notch) with the #160 Main and see how well it works out. I tried the Jetting forum as well and theres no longer any direct link to JD. On an added note for those of you looking for a good jetting chart Motoman has a great one on his site.

http://motoman393.thumpertalk.com/

I'll post the results when i get the chance to get out for a test ride. Thanks All..

[kincade]

Roger,

If you find the spreadsheet, I'd love a copy; I've searched TT and thumperfaq, the link is broken on the latter, and nothing on the former that I can find.

[RogerDedrick]

Roger,

If you find the spreadsheet, I'd love a copy; I've searched TT and thumperfaq, the link is broken on the latter, and nothing on the former that I can find.

I placed a link to it on the page

http://www.lightlink.com/rogerd/jet.html

The one Motomans page on Marks link is short the instruction page and the WR and 250 pages. none of which may be necessary to you but there they are. I will probably leave it there for quite a while in case someone is looking in the archives for this a year from now.

[kincade]

Thanks Roger!

[BlindSide]

Could someone fill me in on these jetting kits please ? I ride the high desert quite often here in East Fort Rock and I'm jetted stock. All I did was drop my needle 2 clicks, adjust my airscrew and it runs like a dream. We're running in then neighborhood of 4000-6000 feet & I guess I'm a bit confused as to why people are buying jet kits, or even rejetting for that matter. I must be missing something.

[Ga426owner]

Could someone fill me in on these jetting kits please ? I ride the high desert quite often here in East Fort Rock and I'm jetted stock. All I did was drop my needle 2 clicks, adjust my airscrew and it runs like a dream. We're running in then neighborhood of 4000-6000 feet & I guess I'm a bit confused as to why people are buying jet kits, or even rejetting for that matter. I must be missing something.

The JD Jet kit will make your bike run more crisp and clean than the stock jet kit - Once you get the jetting sorted out correctly, through testing, the bike will pull a lot better with a lot better throttle response - this kit is comprised of really 2 different needle jets and standard main jets - I only use VP U4 gas and with this kit and the power is unbelievable - You must be the type who likes to tinker with different jetting spec set ups to really get the most out of this kit, as I am in the carb quite a bit more now with this kit for temp changes, altitude and humidity changes. It really works well but patience and testing is completely necessary to reap the benefits of this kit -