I should have my bike back together this weekend, just in time for the massive snow storm that's about to hit, damn it. Anyway, most jetting mods are from you sea level guys but havne't been able to find anything on places of altitude. I have the 351 kit, stock carb, and full Big Gun EvoR exhaust. Anyone ahve some ideas? I usually use my bike more as a street bike with some occassional 8000 to 9000 passes on rides but very little dirt where I need serious, serious torque. I do commute at about 75 MPH on the interstate and would like to actually pass someone from time to time at higher speeds, when needed. Thanks, Daniel.

 

I am at 3300' and run a 124 main because I thought my elevation would mess with it. But I am changing up to a 128 main this winter. I have a stock bore bike.

Everything I have read or heard basically says about a 128 main for a stock bore and a 132 for a big bore. These are DJ numbers of course, different manufacturers will be different sizes.

 

Sounds like a good place to start. I have been running a 125 so I would think the jump from 128 to 132 would probably make sense.

Any ideas about the pilot jet?

 

I went from a 120 on the stock jug to a 128 on a 300cc cylinder and it runs good, but for the first time I'm seeing a fair amount of black soot on the spark arrestor. Haven't pulled the plug, or had a look at the exhaust packing, but judging from the soot and the richer aroma of the exhaust I might be a wee bit rich. (with the 120 jet, the exhaust was like puffs of warm air with no odor at all)

 

I have a 331. Ran a 128 jet prior to the big bore. Bumped up to 132 jet, left the pilot alone, and turned the air/fuel screw out to about 3 turns. Seems to do fine there. I'm going to GUESS that if I bumped up the pilot, I could turn the air/fuel screw in a bit, but, don't know that for certain. I usually ride 2500-about 6000 feet. Seems good, no soot, no bog, no problem. But, I did NOT put a sniffer on it...so, I'm just shooting in the dark.

 

What pilot jet are you running?

 

I have the stock, which I believe is a 35. If I bumped up to a 38, I bet I could screw my air/fuel screw in a bit and have it run just a tad bit better.

It had some popping on decel from high rpms, which tells me it is lean at closed throttle. I think the most-correct action would be to step up to a larger Pilot, but, I was able to quell almost all the popping by running the air-fuel screw out to about 3 turns.

If one of the experts can confirm or deny that I'm thinking along the correct lines, I'd appreciate it. I'm still new to the KLX (still have less than 1000 miles on it!), and certainly don't mind learning when I'm not thinking this CV Carb stuff out correctly.

 

When I had my head at the shop I talked a bit with the head mechanic about jetting and he confirmed what you said above. If you move up one on your pilot then you wouldn't need to have your air/fuel screw turned out so much. I said this because I also had some popping after rejetting with my new exhaust on decelleration. I may even move up two sizes on the pilot, but I think that would be too much since you can't screw the air/fuel screw more then will allow, but you can move it out. I think I am going to start with the 38 pilot and 132 main. By the way, thanks for your thoughts on the topic.

 

I appreciate the feedback....I still have much to learn!

 

Can you update me on the jet setting that worked best? Im in colorado and the elevation range is 5,700 to 9000 at some points. Right now I have the stock pilot 35, the adjustable needle at top clip level and a 120 main jet and it still runs rich. -thanks