"Backfiring" is a condition described as a loud bang, poof, explosion, etc. when idling the engine down, or after the engine has been shut off.
(Note: "Afterfire" and/or "Backfire" will not harm the engine at all!)
"Afterfire" occurs after the engine has been shut off.
Some possible causes include:
Shutting off the engine at high RPM. This can result in some fuel being pumped through the engine and into the hot muffler, causing that fuel to ignite.
Gasoline that contains alcohol has a tendency to ignite easier, plus cause the engine to run slightly hotter. This, combined with a hot muffler, can cause afterfire.
The type of muffler that has been installed by the equipment manufacturer may cause afterfire.
Carburetor adjustments may not be properly set to insure correct engine performance.
If anti-afterfire solenoid is installed it may not be working properly.
Some possible cures include:
Idling the engine down to the proper idle speed for 15-30 seconds. This would allow the engine to cool off some before shutting the engine down Changing to a different non-alcohol or alcohol brand fuel Adjusting the carburetor for optimum performance Contacting the equipment manufacturer for updated designs in air control baffling, mufflers, etc. Checking the anti-afterfire solenoid for proper operation If equipped with an anti-afterfire solenoid, shut engine off at full throttle.
NOTE: This after fire solenoid is specified by the equipment manufacturer
Backfire "typically” occurs when the engine is decelerated rapidly.
Some possible causes include:
Lowering engine speed too fast Gasoline, which contains higher blends of alcohol Carburetor adjustments set too lean Muffler construction can induce backfire Higher than normal engine temperatures Some carburetors can induce backfire due to the sensitivity of internal transitional passages. This condition cannot be corrected
Some possible cures include:
Lower engine speed slowly Change brands of fuel to lower or non-alcohol Adjust carburetor for optimum performance Inquire with equipment manufacturer about increasing engine-cooling air volume by decreasing air restrictions
In any event, your best source of information for any engine concern would be a Briggs & Stratton Authorized Dealer.
NOTE: Please read and abide by any applicable Safety Information (PDF) before performing any engine work. This information is not meant to take the place of work performed by a Briggs & Stratton Authorized Dealer. Terms and Conditions apply to all of our information provided on this website. Always be sure to read and understand your engine Operator's Manual. | 