jetting hmf slip on

[peckerheadracin]

i just installed a hmf slip on on my 04 400ex. i put a 165 main on
and set the needle two clicks up from the bottom. it's running pretty good and sounds great but it is back firing when i let off the
gas at high speed. do i need to adjust the air-fuel adjuster back or in or do i need to change the whole set-up?

[mojoe2878]

if all the mods that you have is the slip on then you are jetted too rich.
i would put the needle clip back in the stock position and try a 152 main jet.

[da400hon]

If it is backfiring then its running too rich. Set the needle back to stock and try a smaller main jet.

[cals400ex]

the backfiring is from your pilot jet. you need a larger pilot jet and turn the fuel screw out a little bit. this should clear up the popping.

what elevation and temperature you ride in?

[EPDP99]

listen to cals hes the jetting man

[nosliw]

Originally posted by da400hon
If it is backfiring then its running too rich.


i've always seen it that backfiring is a common problem when running too lean.....

[meanyellow03ex]

mine's got a 170 keihin mj with the slip on, air filter, and vented lid. runs good. was checked on a dyno. 165 prob. isn't too bad, might need to turn out the screw a half or so.