Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Have a Briggs 11.50 that backfires no matter how much I turn throttle down when shutting off. Sometimes see flames shooting out muffler. Dealer says not much adjustment on carb due to new epa regulations. Anyone have same problem. Mine is a 24" ariens platinum.

Not sure there's much you can do for that. 

Often the backfire is caused by an unburnt fuel/air charge in the muffler.  Once the engine is shut off, the spark stops and there's no longer any ignition source so unburnt fuel will get to the muffler which is often hot enough to ignite the charge.   I've seen numerous engines do this.  As long as the engine is running well, I wouldn't worry about it. 

Have you tried to throttle down and let it idle a bit prior to shutting the engine off?  If you minimize the amount of fuel getting to the exhaust, and allow the muffler to cool a bit, that might be enough to stop the back firing. 

Its most likely running LEAN... i would give the carb a REALLY good clean..and i would check/adjust the valves..

borat wrote:

I have to throttle down for about 30 seconds or so with the Kohler Command 22HP on my tractor or it will produce a very loud backfire like borat stated. Give that a shot and see if it solves your problem before you do anything else.

my craftsman lawn tractor will sometimes do that if it am cutting then lower the engine to idle and turn it off without letting it sit at idle for a minute or so. I suspect that the muffler is so hot from running at full throttle under a load that when you turn the engine off as the engine is spinning down with no spark fuel is still going into the engine, not being ignited and passed into the muffler which in turn can light it off it the muffler is very hot.   

If i throttle down the engine to idle and let it idle for a minute it never does it.   In any case it is nothing to worry about It will not hurt the engine.

carl

Have you tried shutting the fuel valve off and letting it stall out?  I do this on my ancient Tec if I know weather/snow is done for a day or so.  That way I know the bowl is always empty.

as Jt has pointed out, closing the fuel valve will probably help this problem since the engine is shutting off due to lack of fuel and not lack of spark.  When the engine dies from lack of fuel it will not be putting unburnt fuel into the muffler and will probably eliminate  this issue.

specialkkl wrote:

I had a similar problem with my Honda.  My primary jet was partially plugged (this can happen even on the new one) and the dealer cleaned the primary jet in an ultrasonic bath.  No more back firing after the clean.  Ask the dealer to perform a primary jet cleanning job if you have warranty.  Good luck.  It is not going to snow this year.  I may have to cut the grass again - I love this global warming thing!