Fine tuning

[NRPkfx400]

i just bought a header pipe and am rejetting the carb. I put a 170 main jet in and it ran alot better but now when let off the throttle or go down hills it backfires. I think what i need to do is adjust the pilot jet but im not sure. Let me know what your thought are on this. Thanks NRPkfx400

[kellymi]

Try adjusting the fuel screw. I know HMF has a recommendation for this.

[NRPkfx400]

I have an HMF slip on with a FMF header pipe

[drzoo2]

Add an 1/8 to a 1/4 turn on the fuel screw, test and re-tune until the popping on decel goes away. If you reach >3 turns then jump your pilot to a 25 and re-tune.

z

[NRPkfx400]

Thank You

[NRPkfx400]

Wait a minute should i turn it clock wise or counter clock?

[drzoo2]

Clockwise seats the screw and leans it. Counter clockwise makes it richer which it what your after. You added more air so you need to add more fuel.

z