Jetting Confusion!

All this talk about jetting has me all screwed up; 2 quick questions:

1) What's the difference between the adjustable jet needle that comes with the Yamaha AIS removal kit and the JR red and blue needles that I hear about?

2) I ride at 2000 ft with varied weather, but pretty warm in the summer months; I have a 168 main, 48 pilot, Yamaha adjustable needle, 4th clip (came with the AIS kit), fuel screw 2 turns out- does this sound about right?

Thanks to everybody for all the advice in these forums!


Check this link out This helped me big time a few months ago when I was starting my mods.. If you read through all the posts in the first 2 threads of this forum you will find all your answers... Sorry I cant speak for the JD jetting I went with the AIS and also got a #40 leak jet from Yamaha.. Good luck and have fun :thumbsup:

Hi Baja Dave

You jet specs look OK.

I would advise you to search for Indy and Clarks tables for the 03/04 and 05/06 450WRs - they are real close and each bike may only require slight changes to those listed.

The JD needles have different tapers from the OEM and thus (I am led to believe) take a different main. JD Red 4 is probably OK for most bikes and is close to the OEM on 4 I would guess. JD blue was too rich for my bike when the temps got above 15C. The only other thing I would suggest is get a range of leak and starter jets. The 50 STD leak is too big (IMHO) for all but super hot/high conditions. I assume you have a finger adjustable fuel screw? Helps fine tune the idle circuit heaps.

I found the link above did not work. If you want to educate yourself (as I did many months ago) then read all the articles in the jetting forum for the FCR carb and the Basic info as well. Very soon you will be able to diagnose what is happening AND how to fix it - very satisfying. There is nothing difficult about it once you know cause and affect. Burned is always willing to help out as well.

Whether you switch from OEM is your choice, many have said the JDs are not worth the cost and the OEM provides ample performance and adjustability.

I have found the 06 WR is quite sensitive with the JD setup (probably with OEM as well). I have changed my jetting 4 times as the temps went from 15 to 30C+ and humidity rose as well. I prefer keeping the bike slightly rich though.

Post again if you have specific problems. :thumbsup:

Thanks for the help guys!

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