Comments on: What Causes A Lawn Tractor To Backfire?

By: Engineer

Engineer — Mon, 08 Feb 2010 07:16:53 +0000

Is it backfiring through the carburetor or the exhaust? Carburetor means really bad spark timing or a leaky intake valve; backfiring through the exhaust generally means you’ve got an ignition miss that allows unburned mixture to leave the engine and then get ignited by the next shot of hot exhaust.
I’d start by looking at the spark plug and wire. If the spark plug is clean and gapped properly (use a feeler gauge), start it up when it’s dark out and see if there is any sparking around the coil, plug wire or boots. Failing that, go to a mechanic and have the engine checked.

By: smashtk

smashtk — Mon, 08 Feb 2010 01:23:45 +0000

“In general, backfiring on deceleration (as opposed to acceleration) is generally caused by a lean condition in the pilot circuit. What happens is that the mixture leans out enough to where is fails to ignite consistently. This, in turn allows some un-burnt fuel to get into the exhaust pipes. Then when the engine does fire, these un-burnt gasses are ignited in the exhaust pipe, causing the backfire. Newer Virago carbs have an ‘enricher circuit’ which cuts in on deceleration to help this problem. Earlier carbs do not have this. I would say check the pilot circuits, and set them a bit richer. It is hard to do this right without some equipment to test where you are. Aftermarket pipes often increase backfiring, probably because they may the bike run leaner.”

By: dcs997

dcs997 — Sun, 07 Feb 2010 18:56:06 +0000

it may be the ignition timing. A backfire happens hen the spark plug fires out of time and the valve is open. Sometimes it may just need a new spark plug. Try that first.

By: Bighorn

Bighorn — Sun, 07 Feb 2010 16:39:48 +0000

they will backfire if you dont throttle it down to idle before turning it off. let it idle then shut it off