JD Blue vx Red and Main Jet

[Kmorris]

Is there any relationship between using the Blue or Red JD needle while experimenting with the main Jet - example:

Staying with the Blue needle (#3) and switching to a 168 or 165 main (from 170) or switching to the Red needle (#4 or #5) and staying with 170 main.

Can needles and jets be interchanged I guess is the question.

[Indy_WR450]

Yes you can interchange jets and needles.

The blue needle is for winter and used in summer for heavily modified bikes with loud pipes. Summer time the red needle will give you more crisp throttle response in the 1/4 to 3/4 throttle range. ?

[bg10459]

The pilot circuit controls from idle to about 1/4 throttle, the needle from about 1/4 to 3/4 throttle, and the main from about 1/2 to WOT. All circuits overlap to some degree, too. So if you've got a WOT problem it is most likely a main jet issue. Running a richer needle (blue) with a leaner main jet will not get you the same results as running a leaner needle (red) with a richer main jet. You should address each circuit individually, starting with the main jet, then the needle and clip position, and then the pilot circuit.

Check the Thumper Jetting FAQ for the details, or just start with Indy's jetting chart. He knows his $hit, so it'll usually get you pretty close.

[silverlakerider]

The blue needle is for winter and used in summer for heavily modified bikes with loud pipes.

Indy, please clarify heavily modified and what you consider a loud pipe? I've followed your jetting chart to the letter and my bike (05 WR) still isn't perfect. It's starting to get annoying.

[Desracer]

Use the red needle in #3 from the top with a 168 main jet and 48 pilot jet on your 05. Fine tune for starting with your fuel screw. The blue needle can be used for a wall pin. The 170 main with the YZ pipe with red needle ran stronger than with the blue across the board. Remember the 03 and 04 WR's are not like a 05 for jetting. Some extra air box holes also help, try running the bike with the filter side cover off. If it runs better with more air flow add some vents. With this jetting I can get up to 35mpg. Hope this helps.

[silverlakerider]

Use the red needle in #3 from the top with a 168 main jet and 48 pilot jet on your 05. Fine tune for starting with your fuel screw. The blue needle can be used for a wall pin. The 170 main with the YZ pipe with red needle ran stronger than with the blue across the board. Remember the 03 and 04 WR's are not like a 05 for jetting. Some extra air box holes also help, try running the bike with the filter side cover off. If it runs better with more air flow add some vents. With this jetting I can get up to 35mpg. Hope this helps.

That's exactly what my jetting specs are. It still hesitates slightly on decel or once in a while at steady throttle. It's a helluva lot better that it was when I started but's it's not perfect.

[Kmorris]

Desracer,

What are your conditions, temp and alt?

Thanks

[Desracer]

I start at 3200ft and can go to 10,000ft. I ride all year long if not hurt. I was racing GP off road last year with the same carb settings. The only change was to open up the exhaust with a one inch tip which gave me great top end pull. The 170 main works good with opened up exhaust but sucks gas bad, approx 18 mpg's. I have noticed that since it has gotten above sixty degrees it is starting much better and I have been able to turn in the fuel screw. I would say overall the jetting is close with this red needle. I would like to try a YZ needle to compare. I run a tad fat with my set up but my header doesn't glow and the engine stays cooler also.