Jetting problem?

Recently bought a '07 yz450f, in great shape, but I believe it is running a little lean...backfires and pops on deceleration and it idles up and down constantly when in neutral or when clutch is engaged. Has a fmf exhaust with the powerbomb I believe it's called? Correct me if I'm wrong.... and a hindle pipe, I'm wondering what I should run jetting wise? At about 300ft above sea level aswell as 0 to 30 degrees celsius, any help is appreciated thanks!

Edited by Ch35450

Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.

Have you gone through the process of setting your idle properly, I found that will tell you if your pilot jet is right. You probably need to go one size up or maybe it just needs to be cleaned.

Yeah I messed around with it for a little and it still responds fine but even set at a lower idle it will still wander up and down by itself

How many turns out is the fuel screw?

Wandering idle is a lean condition, likely caused by a dirty carb.  Also these bikes tended to be jetted lean which can also cause a hanging or erratic idle.

The wandering or "hanging" idle can also be caused by tight intake valves.  When they're too tight, they set up a lean condition by leaking combustion chamber pressure back into the intake tract and disrupting the airflow.

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