Just bought a 2001 WR 426. Has an FMF pipe, no air box lid. Main is a #165 and pilot is a #42.these are stock jets according to shop manual. My elevation is 2500-3000 Ft. Any ideas on jetting?

Manual says - VT 1100 88-96 main Jet both nr.165, slow Jet 42

For VT C2 and 1100T main front 175, rear 180 , slow 42

For 97 main both 178 , slow 42

You can read Nr. on Jets, they are small

Try covering up the holes in the airbox (where it has been cut away) with tape. If it runs better, you know the jet size is too small. Sometimes the jet kits don't go big enough for a modified airbox.

JD jet kits give you a few options

I ended up using The red needle at 5 notches down
up from 165 to 170 main.
up from 45 pilot to 48 pilot

You might just want to try a 170main first and see how it goes

165 main jet and 42 pilot jet

Hi and welcome to FixYa,

On a 2003 Kawasaki KLX125, these are standards:

• main jet - 145
• pilot jet - 17.5

Good luck and thank you for asking FixYa. Happy Holidays.

I have an 04 125 with a FMF fatty Factroy expansion chamber and a Titanium 2 FMF silencer (shorty) the carb settings are Pilot a size leaner than stock main IS stock jet needle is a setting toward lean and air screw is two turns out. My gas:oil mix is around 32:1 - 40:1.. My spark plug buget is killing me, and I havemessed with it til I was blue in the face can anyone help me?,don't worry I didn't take it wrong it is a good question, and let me put it this way.. I run it like a two stroke lol I have had more than my share of two strokes so I don't lolly gag it and usually for the trails I ride you really can't get out of 1st most of the timeI spend most my time around 3/4 throttle. When I 1st got the bike I had a friend messing with the idle screw on it cause it wouldn't idle at all and he messed with the mix screw by accident so I think it was screwed out more than two turns but I set it according to FMF recommendations with the pipe and chamber. The guy who had it before me raced it in a AMA class I don't know which so don't ask lol, so who knows what has been done to it other than what I can see,,,

I have an 04 125 with a FMF fatty Factroy expansion chamber and a Titanium 2 FMF silencer (shorty) the carb settings are Pilot a size leaner than stock main IS stock jet needle is a setting toward lean and air screw is two turns out. My gas:oil mix is around 32:1 - 40:1.. My spark plug buget is killing me, and I havemessed with it til I was blue in the face can anyone help me?,don't worry I didn't take it wrong it is a good question, and let me put it this way.. I run it like a two stroke lol I have had more than my share of two strokes so I don't lolly gag it and usually for the trails I ride you really can't get out of 1st most of the timeI spend most my time around 3/4 throttle. When I 1st got the bike I had a friend messing with the idle screw on it cause it wouldn't idle at all and he messed with the mix screw by accident so I think it was screwed out more than two turns but I set it according to FMF recommendations with the pipe and chamber. The guy who had it before me raced it in a AMA class I don't know which so don't ask lol, so who knows what has been done to it other than what I can see,,,

I have an 04 125 with a FMF fatty Factroy expansion chamber and a Titanium 2 FMF silencer (shorty) the carb settings are Pilot a size leaner than stock main IS stock jet needle is a setting toward lean and air screw is two turns out. My gas:oil mix is around 32:1 - 40:1.. My spark plug buget is killing me, and I havemessed with it til I was blue in the face can anyone help me?,don't worry I didn't take it wrong it is a good question, and let me put it this way.. I run it like a two stroke lol I have had more than my share of two strokes so I don't lolly gag it and usually for the trails I ride you really can't get out of 1st most of the timeI spend most my time around 3/4 throttle. When I 1st got the bike I had a friend messing with the idle screw on it cause it wouldn't idle at all and he messed with the mix screw by accident so I think it was screwed out more than two turns but I set it according to FMF recommendations with the pipe and chamber. The guy who had it before me raced it in a AMA class I don't know which so don't ask lol, so who knows what has been done to it other than what I can see,,,