backfiring

**stephane** · #1 9 Aug 2003

bike ivj keeps backfiring after deaccelaration slowly getting worse apart from backfiring running fine could possibly be, ive made alteration to airbox closing original intakes and removing service panel after this alteration is it necessary to change jetting as seems to be sucking more air ,what are other causes of backfiring cheers

**Davmit** · #2 10 Aug 2003

Backfiring is normally a sign of a weak mixture. Try blanking off a portion of the opening in the airbox and see if this makes any difference - although unlikely. It is however often caused by a loose exhaust pipe to Head joint or blowing gasket here. Another major cause can be a burnt exhaust valve.

**Steve Pickford** · #3 12 Aug 2003

Also try re-setting the mixture screw on the under side of the carb. I'm not familiar with XT's but you'll probably find it on the the cyl.head side of the carb. If so, it will probably be controlling fuel at tickover. Screw it in finger tight & no more and then screw it out approx. 1 to 1.5 turns. Try this on a hot engine. the backfiring should decrease. If not screw it out in eighth of a turn increments. If it still does not cure it by the time you're 3 or 4 full turns out, then it is a leaking exhaust or carb manifold.

If trying this, it is worthwhile taking the screw right out, watch out for the spring (sprung loaded on some bikes) & greasing it prior to screwing it back in finger tight (no more!!). Seized mixture screws are a pian in the arse.

**stephane** · #4 16 Aug 2003

cheers for the replys i havent had a play with the bike just yet but i think i know what the problem is the front racks i made for fuel cans dont allow the headers to fit snug so its out with the grinder once more