Colorado jetting?

I just got my '05 WR. Just like everyone in the group says, the thing is hard to start when cold and runs way lean. I've ordered the JD jet kit and the Zip Ty fuel screw, and I will make the other free mods. I probably won't be getting an aftermarket exhaust - I need the bike to be quiet - below 96db - for the Colorado 500 sound test. Any chance of meeting that with the stock exhaust and the muffler restrictor removed?

I will be riding my bike in Colorado at altitudes mostly between 6,000 and 9,000 feet, with occasional rides up to 12,000 feet. I also take the bike to Moab once a year.

Would any Colorado riders care to tell me their jetting and other setup to get me started?

How sensitive is the WR to altitude changes? I jetted my XR for about 7,000 feet and I could ride it anywhere from 4,000 to 12,000 feet (which means that it had no power at any elevation :-). Will the Yamaha be as accommodating, or will it require rejetting for trips to Moab?

Thanks for your tips.


I have a 2003 WR here is the jetting I have used on the 500. 160 main, 45 pilot, pilot screw 1 3/4 out, needle in stock position.

The stock muffler with the insert will test in the area of 92 DB. If you remove the baffle it won't pass. You can try a different insert and it will be close but should pass. I have heard good things about the GYT. I have a FMF Q that passes the 500 sound test.

FWIW I have not noticed the bike being that sensitive to altitude changes.

160 main, JD red #4, 45 pilot works well in Colorado in the summer. You can go al low as 155 main, JD red #3 , 45 pilot for hot high altitude rides. Most of the time it is very cool at 12,000. feet even in the summer. :cry:

I bought my '05 in Albuquerque (5300ft) and the dealer put in a 155 main jet. The salesman/manager rides WRs so they seemed to know what they are doing as they un-corked it, cut the throttle stop and jetted it. When I got it home to Santa Fe (7000ft) it stumbled up top. Removing the snorkel got rid of 97% of the top end mis, so I'm guessing a 150 main is what I'll end up running. Haven't read the plug though - waiting for it to get warm.

I ride in Colorado a lot and didn't realize they had sound restrictions. Does one need some sort of ORV sticker or plate in that state? What are the implications of riding with the exhaust restrictor removed? Will a cop/ranger pull you down and break out a DB meter?


All National Forest and BLM land you are suppose to run a spark arrestor and meet a 96DB max sound limit. Some states/areas have more restrictive sound limits. The sound limit is rarely enforced in Colorado. The orginal poster is going to ride in the Colorado 500, an organized charity ride. They strictly enforce the 96DB limit.

To ride on the public lands in Colorado your suppose to have a Off Road Vehicle permit from Colorado or your state. Or you need to have a license plate for your bike.

I have a similar jetting question. My '02 WR426 ran great until after I'd gotten it mired in 'Colorado Clay' mud, where all the vent tubes got plugged up and the plug fouled (looked oily and black = too rich?). Since cleaning up the bike and routing the top carb vents into my airbox, the bike will start just fine, and give every indication of good throttle response when it's warmed up, but it hits intermittent flat spots when I'm riding where it feels like it's not getting fuel, or it's getting too much fuel. I have done nothing to the carb as far as turning screws etc.

I have no idea what the jetting is, but my guess is that it's stock. Like I said, it ran great last year between 5k and 12k feet. Now it runs like shit, ever since the mud fiasco. Is it dirt in the carb? Do I need to re-jet? I have never pulled the carb off and attempted this, but maybe it's time. What's the best main jet & pilot jet combo to use in Colorado (5200' to 12k')? I want something that will work well just about everywhere, so I don't have to mess with changing jets or turning screws when I ride at higher altitudes.

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