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Why is my petrol mower smoking?

I have a flymo petrol mower with a briggs & stratton 450 series engine. I started it today and it billowed white smoke from the muffler. It does do this occasionally but usually it stops after a few seconds of running. This time it it didnt ease after a minute or 2 so I stopped the engine. What worried me was that there was still a small plume of smoke rising from the muffler for a few minutes after stopping the engine. I topped up the fuel just before starting it but haven't overfilled that. I checked the oil level and that is spot on so I didn't need to put any oil in. The mower hasn't been tipped in any way as I am paranoid about fluids coming out.
Can anyone help me with why it is doing this and an idiots guide how to correct it. I was worried about letting it run in case it caught fire in any way and the little plume of smoke was as if it was smoldering somehow. Thanks in advance

k handbury
July 2010

Briggs & Stratton Garden Tools, Lawn Mowers Petrol Mower Flymo

I would firstly check the oil level. Remove excess or top up where necessary. Take out foam air filter and if saturated in oil squeeze out excess, wipe with absorbent paper towel and replace. Start engine and run and see if white smoke decreases the longer it runs

pleasant
July 2010

Thanks for the replies especially that breakdown Pleasant. So do you think I should run it to burn the oil off or take it to be looked at? It does have extra insurance on it but i imagine the recommended service places are pretty far away. They usually are with these things.

k handbury
July 2010

"I started it today and it billowed white smoke from the muffler" That suggests to me it wasn't smoking when it was last used and could indicate a storage problem.

"It does do this occasionally but usually it stops after a few seconds of running" Hmmmm...... doesn't sound like a worn engine to me otherwise it would be burning white smoke all the time. Certainly suggests oil migration into the breather/exhaust with the excess being burnt off after initial starting.

"This time it it didnt ease after a minute or 2 so I stopped the engine. What worried me was that there was still a small plume of smoke rising from the muffler for a few minutes after stopping the engine" That suggests an excessive build up of oil in the exhaust which is continuing to smoke from exhaust heat. A worm engine would not continue to produce smoke after being stopped.

pleasant
July 2010

If-after 32 years of working on briggs engines you believe that because someone hasn't tipped the mower on its side or overfilled with oil it rewuires a new engine or short block then good for you. At all the MST courses I have attended there are far more reasons for the symptom of burning oil than simply jumping to the conclusion the engine is knacked.

pleasant
July 2010

Correct me if i am wrong, but did they not say it had not been tipped, and not been over filled, does that not suggest it is an internal problem with the engine, after 32 years in this trade, 8 of which being a Briggs master technician that is where i would now be looking

Husqvarna man
July 2010

"there is no simple way to fix this, its either short block or new engine" In 15 years of repairing Briggs engines I would never expect that to be the case. Especially on a 450 series engine- that makes in no more than 3 years old.

Like previously stated there are several reasons for white smoke and all of them are due to the engine burning excess oil.

A. Mower has been stored end up causing oil to enter the combustion chamber

B. Crankcase overfilled with oil

C. Mower has been tipped on its side with exhaust side down whilst also moving the blade manually for cleaning purposes.

D. You are using a 2-stroke (oil/petrol) fuel mix.

pleasant
July 2010

Stating the obvious it is burning oil, if you wre sure it has not be tipped and has not been over filled, then it has to be engine wear, there is no simple way to fix this, its either short block or new engine

Husqvarna man
July 2010

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Why is my petrol mower smoking?

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