backfiring again

[dirtdawg]

i'm running a 110 main with a 40 slow jet with the airbox lid removed and an fmf powercore 4 slip-on and i still notice backfiring when i let off the gas after bumping up the jets from stock. it is worse when in neutral then when actually riding. I never change the plug from my last set up and it seemed fouled because it was sooty and black on the top. So, what is it? do i have to get a size 42 or 44 slow jet,or do i simply need a new plug? also, what # plug, 7 or 8? let me know. thanks. i can post a sound bite if you want.

[BR16250]

definitely get a new plug, they will probably have a book with the size u need at the store...put your stock pilot jet back in. that should probably help

[the Z Man]

Exhaust leak... try a new donut.

[dirtdawg]

its had the same gas since february. would that affect the problem? also, i never mix my gas. i always fill it up with regular gas from the pump, not super unleaded or anything special. also, i don't think putting the old slow jet back in would help beacuse it was backfiring before with the size 38 slow when i let off the gas. the slow controls idle to 1/4 throttle so since it only backfires when i let off the gas, i thought that would be the problem. and just out of curiosity is the donut the thing that connects the header pipe to the slip-on muffler? if so, i'll see if i can tighten that any. i don't think that's the problem though.

[BR16250]

its definately the spark plug, get a new one and post back

[dirtdawg]

i give u props z man...it was an exhaust leak. i just had to tighten up the clamp or donut and no more backfire! thanks a lot man!