Backfiring when throttle is backed off

[Anonymous]

Well the title says it, i am now riding my bike on a regular basis and i put new plugs in , gave it a oil change with mobile 1 fully synthetic and new filter. I synced the carbs the best i could but have the equipment to do it again. I also rebuilt them and now i turned my air mixture screws out to 3 turns because 2 were not doing anything. The question i got is What causes backfiring when the throttle is backed off after reving and why does my bike not get great gas mileage is it because its a 1100 cc. What do i need to do to fix the backfiring. Thanks for your help.

[Anonymous]

100 cc bikes usually get excellenyt gas mileage-over 40 at least. Again--What color are your plugs burning now??

[sharpy]

Back firing

Back-firing = lean, checked for ill fitting inlet (Front & back of carbs)rubbers as you have removed the carbs. Remove plugs and check same color on all four plugs.

[Dink]

It is also possible that it is running so rich that it is in fact raw fuel igniting in the pipes. What colour are your plugs?
Dink

[Anonymous]

I will pull my plugs monday when i have off work or sunday which ever is possible, how do i put a picture of them on this site so you guys can see what they look like?

[KEITH KRAUSE]

Normally,when you adjust the side air-screws out more,the backfiring will increase. It is a lean condition. Try about 1 1/2 turns out and re-set idle.

[daveo]

also a leaking exhaust gasket at header pipe will backfire when throttle is closed, and,a too lean a pilot air jet will do it

[Anonymous]

Did you fix this problem ?

My 850 has started doing the same thing.

[frosty5011]

Madoc,

I also have this with my 850, the reason for it being (in my case) the actual muffler....where it is clamped into the pre-muffler (crossover) has with time, pulled itself out far enough to where the "notched gaps" are showing. This allows the cold air to be sucked into the exhaust, creating the backfires.....especially when letting off of throttle.

You can undo the clamp....and push muffler further into the assembly and reclamp tight...but with time it just wants to "slide out about 1/2 inch and expose those gaps again.