10,000' Altitude Jetting

Some buddies and I are going to Colorado to do some riding and all of us are jetted for sea level. What jetting setup is good for 10-12k feet?

Thanks! Jeff

45 pilot, 146 to 150 main jet, and raise the needle clip one position.

I'd probably go with about a 155 main. The 160 is a little lean yet at sea level. The 04's came with a 165 and I run a 168 - 170 most of the time. The 03's really had some screwed up jetting.

Jetting is a compromise. Especially in Colorado. If you are just going to be runnin around the Rampart Range (close to Denver) your altitude is only gonna vary from about 7800 to 9200 feet. If you are going to be around Salida or Telluride or Taylor Park your altitude will vary quite a bit more in one days ride.At Salida or anywhere around the continental divide you will start at around 8000 feet and can top out at around 14000. Thats on the extreme side such as a climb up Mt.Antero. But you are quite likely to go from 8000 to 12000 when you go over any mountain pass. Luckily the WR450 handles altitude changes as well or better than any bike I've owned. I think most riders who change from lowland to mountain riding frequently will say the needle is your most critical jetting change. Going from sea level to 10000 feet or more you need to raise the clip 2 notches (that drops the needle two notches). I run my needle in the top notch because I frequently get above 12000 feet. I run on the carburators needle and pilot circuits most of the time at those altitudes. If you are on a 10 inch wide single track with a 100 foot drop on one side and a sheer cliff straight up on the other you probably wont be on the main jet. I run a 160 main for altitude and a 170 main at 3500 feet where I live.I havent messed with my pilot in so long I dont know what it is. I remember I richened the pilot from stock and it runs fine at 3500 to 13500 with a little tweaking with the fuel screw. Everything gets a little breathless at 14000 feet and I bet you do too. Have fun and be safe up there. Tim

Thanks a lot you guys for all of the input!! It really helps out.

Jeff :thumbsup:

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