Backfiring, Ignition Governer, Jetting

[salz]

At the higher altitudes (7,500 feet and up) my '02 WR426 backfires quite a bit - any suggestions - see jetting & mods in my signature below.

Also, the WR starts fine, idles fine, runs really good from 0 throttle to 3/4 throttle. Problem is if I am at a

standstill in first gear (or going slow in 2nd or 3rd) and hold the throttle wide open for a few seconds at

the higher revs it is "cutting out" or "mis-firing" (sort of difficult to describe).....could this be the

jetting set up, or could it be the timing, or could it be the governer kicking in (some have said it is just

the governer doing it's job- I'm not sure).

Any advice would be appreciated..... ?

[dominator426]

Sounds like you're a bit lean on the main fuel jet. Did it worsen in colder outside temperatures? What type of fuel are you using? Also, you may have to cover part of your rads to achieve a good engine operating temperature...