08 yz450f jetting

Hey guys I just have a quick question. I just bought an 08 450f and I was wondering about jetting. It is quite cold here (in the 20's) in tennessee and I have noticed that the bike runs lean in the cold and the header pipe glows red real fast like under a minute. When the temps were in the 60's it would take minutes for the header to glow. My question is how big of a jetting adjustment should I make when the weather hovers in the 30's?


you should increase the jet size by 2% for each 15-20 degrees dropped. So, from 60 to 30, you should go 4%, which is from a 160 to a 165, and a 45 to a 47 (or a 48).

Once the temps dropped here I went to a 48 pj, no change to the main or needle clip position and the bike runs good.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now