WR426 Jetting for Colorado 5k to 13k

Anybody have spot on jetting for a WR426 running in Colorado?

I ride from 4k (Moab) to 5k(Denver) to 7k(Rampart Range) to 12k(Crested Butte).

Have dropped to a 150 main, but think that's too lean. Dealer left in a 160, which foulded like crazy. Read from others that a 150 works for them. Also read others are changing PJ's with better success than leaning out the main. Dealers don't have much to offer around here...

I have a 2001 WR426 w/ YZ timing and silencer core removed. A buddy has a stock WR426, so any additional advice would be appreciated.

You ride the exact places I do. I have an 01 YZ426, stock jetting except 158 main and tweaks to the fuel screw. Drop to a 152 (153? I cant remember) for Crested Butte. I have an Excel jetting spreadsheet if you are interested.

I ride moab,grand junction and crested butte as well.I will await jetting tips as well


For high altitude riding check out the "Technical" section article written by Clark. (Look to the left) He recommended a DVP needle in clip #3. You could just try using a leaner clip position, but the DVP is what I would consider a better alternative to your stock jetting. That and fine tuning the pilot (fuel) screw.

Changing the main jet is not going to cure plug fouling problems.

The carb needle in the YZ426 uses more taper and will need a smaller main jet by about 2-3 steps from the WR OBD-- carb needle.


Sorry about the bad info. I did not know that the carb setup was different between YZ and WR. James, where is the article you are talking about?

[This message has been edited by mikeolichney (edited 05-15-2001).]

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