Top end stutter

[redzoomer]

I put a HMF pipe on my son's 300ex, I went to the HMF website and changed the jetting as they recommended. Also put in a UNI airfilter.
it revs good runs good until you start winding it out. once it hits 3/4 to nearly full out it starts Porky Pigging... de de de... de de.. de
You get the picture.
I've moved the clip up on the needle and back to the middle.. no better. adjusted airscrew.. even cussed and fussed at it.
I've never in my life ran into this! It does pop a little on decel..
Any body got any ideas?

[wilkin250r]

3/4 to full throttle sounds like a main jet.

Popping on decel sounds like an idle setting, either an air screw adjustment or pilot jet.

[chad502ex]

bobbling on top end tends to be rich....

backfiring/ or popping on decel is lean pilot....

i would raise pilot one size and lower main one size... do one jet change at a time, not both...

good luck.

[redzoomer]

I raised the pilot to 40.. not much difference.. still stuttering.

[JOHNDOE83]

the pilot is only for the backfiring, the main being to big will make it stutter on top end.

heres a plug reading and jetting info thread I started.

its more detailed in the 400ex section of the forum.

http://www.exriders.com/vbb/showthread.php?s=&threadid=441851


if you need more help just post and ill try to reply asap.