Super Quick Jetting Question- YZ426---From 6500ft to 2500ft

I know this has been covered but thought I'd ask. I have a 2001 Yz 426. Stock pipe, spark arrestor, I think thats it for the motor.

I am racing a rockcrawler out in CA, leaving monday. I will be prerunning on my YZ250 and bringing the 426 for a friend to ride. I have a bunch of jets, JUST WONDERING WHAT TO THROW IT THERE?

Its about 2500ft above sea level. I would like to run a little rich so I don't pop the motor.


Check the user jetting DB in the stickies at the top of the page.

Rule of thumb is that the jetting will change roughly 1% per thousand feet. That means that you'll go up one jet size (from 165 to 168 or 168 to 170) for each 1500 feet of altitude lost in the descent. Same applies to the pilot.

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