Tip & How-To about Garden

Lawnmower fuel pop

Does your lawn mower or small engine give a big pop or bang when u shut it off after it has run and heated up for a while? I think this is from the hot exhaust egniting the gas fumes still coming through the engine. This may clean the carbon out of the muffler, but it may shorten the life of the head gasket. Either or it sure does scare bystanders, and wakes up the neighbors. To keep this from happening, just let the engine run at low idle for 30-40 seconds before shutting of the spark. Works for me.


Posted by on

Garden Logo

Related Topics:

Related Questions:

1 Answer

I have a briggs and Stratton 22 hp Intek V-twin engine on our Craftsman riding mower. After about 30 minutes of mowing the engine suddenly began to run rough, loud and out of sync.

my thought is the valves are out of adjustment. that is the popping you hear or backfiring. i think if you take off and clean the carburetor and set the valve lash it will probably run like a new one.

May 17, 2016 | Garden

1 Answer

Engine backfires, runs only at low rpm, seem to be flooding

The unit in the bottom of the float bowl is an anti fire solinoid, when the ignition is switched off a small needle is inserted into the main jet in the carb, the idea is to stop fuel entering the engine as the engine shuts down, if fuel enters the engine as it is shutting down it is sent out the exhaust valve and into the hot exhaust, this in turn can and does cause a massive bang, you can test this by removing the unit from the bowl, switch the ignition on, the centre needle should retract into the units body, if not it is bad and will stop the engine from reving.

Apr 06, 2013 | Craftsman YT 3000 42" Briggs & Stratton 21...

2 Answers

What would cause the lawn mower to stop running when not out of gas? If you give it a few seconds and restart it it will run again for awhile then stops. I have noticed if I pump the primer a couple of shots it will start right back up then run for a few minutes or even ten minutes before it shuts down again.

Try using non-ethanol gas. It's death on small engines. Starter fluid gives it a boost if higher octane. Have a reputable repair place clean out the gunk, then use good gas. Best of luck finding non-ethanol. Boating marinas carry it.

Jul 20, 2010 | Mtd 22" Yard Machine Push Mower

1 Answer

I found a big mouse nest on top of the engine and now my mower runs for 30 seconds then stops. Do you think the heat damaged the valves?

For you to have found a mouse nest on top of the engine, then that tells me that it's been left idle for a long time. Like maybe as long as over the winter.

The 30 seconds is about the time it takes for the engine to run the carburetor dry. If left along for another while then that'll allow time for more gas to reach the carburetor and then run again until it repeats it's cycle.

You may have to remove the carburetor and give it a real good cleaning. No, i don't think the heat has damaged the valves because if it had, then the engine wouldn't start at all because you'd have little or no compression.

Look at the carburetor you may have had a dual problem there and one is not related to the other.

Hope this helps and good luck.

Oct 03, 2009 | Troy Bilt 5.5hp Self Propelled Mower

1 Answer

My cub let out a big ploom of white smoke and shut off.

This is caused by two things low oil level and overheating, The oil also has a cooling agent in it so if it was run low the engine would not get lubrication and overheat possibly causing the conrod to break if you say its only 10 hrs old i would be talking to the dealer you purcased it from or the engine manufacturer. its unusual for an engine with very little hours on it.

Jun 29, 2009 | Cub Cadet Street Sign- tractor lawn riding...

Not finding what you are looking for?

174 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Garden Experts

Dennis Key
Dennis Key

Level 3 Expert

2475 Answers

john h

Level 3 Expert

11064 Answers


Level 3 Expert

75077 Answers

Are you a Garden Expert? Answer questions, earn points and help others

Answer questions