Why do mowers smoke after being on their side?

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SOHCman

SOHCman

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For blade sharpening, an oil change or what not, it seems I get a puff of white smoke on the initial startup after after past mowers have been over on its side.

Does oil make its way past the rings? through the valve guides? maybe the breather tube?

I always used to get the puff on an old brigs that is now gone, but Im sure that was from wear. My one season old Toro with the 159cc toro OHV engine just gave off its first puff of startup smoke, which its never done before, but to be fair it wasn't just on its side, I had it nearly upside down for under deck maintenance.

It's had about 4 oil changes of Rotella T5 at this point, and never a lick of smoke before, but the mower never went past resting on its side wheels.
 
Keep the carb side up for this and that should reduce the oil from the sump draining to the intake. I would not turn in upside down with oil or gas in it. Some people have had enough oil in the cyl that it won't turn,( liquid won't compress) they junk it thinking its bad, when all you have to do is take the spark plug out and drain oil from the cyl head.
 
like spasm3 says, keep the carb up.

My wife mowed once (Briggs quantum), a long time ago, and couldn't get it restarted...I came home and tried, and couldn't get a start, then noticed oil dripping out the air filter. It was clogged with oil.

She never mowed again, and I've not had the problem again.

Was getting weed whacker cord one day, and a guy came in with a "blown up" ride on, had cleared some stuff and it wouldn't run...I showed him what needed doing, and Kermit (the mower shop owner) ripped me a new one as a $150 service was his standard fee for an oil soaked aircleaner.
 
My riding mower gets oil in the cylinder if I'm mowing on a steep downgrade and if the oil is overfilled.

I had an episode last week where I forgot to close the fuel shutoff after mowing, and the fuel tank drained into the cylinder. The engine wouldn't turn when I tried to crank it, so I took out the spark plug and got a huge bloosh! of fuel. Predictably, the oil level was overfull, and there was a lot of fuel in the oil. Since I was in a hurry, I mowed anyway and got it done without killing the engine. I figure it gave the engine a powerful solvent flush. I changed the oil (VR1 10w30) and filter (B&S Yellow), and it was ready to go again. These days I am mowing two lawns with it, and it works just fine.
 
Originally Posted By: zzyzzx
This is on my long list of reasons why I prefer electric or human powered mowers, electric chain saws, and electric weed whackers.


But those won't keep the mosquitoes at bay. I've got one Honda mower that gives out a puff of smoke on every start. No bites!
 
Originally Posted By: SOHCman
For blade sharpening, an oil change or what not, it seems I get a puff of white smoke on the initial startup after after past mowers have been over on its side.

Does oil make its way past the rings? through the valve guides? maybe the breather tube?



Briggs & Stratton and Kohler engines (I don't do Honduh) have the oil breather assembly on the side of the engine. Inside it there's a small hole into the crankcase and (in some cases) a check-valve and a vapor/gas separator consisting of wire mesh. The check valve lets gasses puff out when the piston moves down, then not rush back in when the piston moves up, giving a sort of PCV effect. The air then goes through a breather tube to the carb, behind the air cleaner.

When you turn the engine on its side, liquid oil can run into the crankcase breather, and from there it gets pumped to the carb, sucked in, and burned. It can also drench the air filter sometimes.

On the flathead Briggs engines, the breather is on the side opposite of the carb, so if you have to tip the mower on its side you want the carb DOWN (contrary to the advice a few posts above) to avoid getting oil into the breather. Other engines are different, the breather is usually a flat stamped sheet-metal plate on the side or top of the engine with a couple of screws to hold it in place. Just make sure the breather is on the "up" side when you tip the engine regardless of whether it puts the carb up or down. The carb's going to dump a little fuel no matter what you do.
 
Oil can get passed the rings and into the combustion chamber if tipped up at the front when the spark plug is on the back (operator's) side.

If tipped on its side, some oil may run into the muffler if the exhaust valve is open and so when the muffler gets hot, it smokes.

Luckily, on my mower, the spark plug is at the front so when I tip the front of the mower up to remove the blade, no oil flows past the rings into the combustion chamber.
 
Last edited:
Originally Posted By: Bluestream
You've done 4. Oil changes on a one year old mower???seems overkill


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Originally Posted By: MolaKule
Oil can get passed the rings and into the combustion chamber if tipped up at the front when the spark plug is on the back (operator's) side.

If tipped on its side, some oil may run into the muffler if the exhaust valve is open and so when the muffler gets hot, it smokes.

Luckily, on my mower, the spark plug is at the front so when I tip the front of the mower up to remove the blade, no oil flows past the rings into the combustion chamber.


I'll have to try tipping the front up, I have always tipped to the side, but I may like that better. Maybe put a concrete block on the handle to hold it down.
 
Originally Posted By: spasm3
Keep the carb side up for this and that should reduce the oil from the sump draining to the intake.


That don't work because while it's tipped on its muffler side, oil runs into the breather, THEN, when I tip the mower back upright on its 4 wheels, the oil runs from the breather, across the breather tube, and into the carb! So in essence, I'm hit with a double whammy: Smoking on start up AND oil in the carb.
cry.gif
 
Originally Posted By: Merkava_4
Originally Posted By: spasm3
Keep the carb side up for this and that should reduce the oil from the sump draining to the intake.


That don't work because while it's tipped on its muffler side, oil runs into the breather, THEN, when I tip the mower back upright on its 4 wheels, the oil runs from the breather, across the breather tube, and into the carb! So in essence, I'm hit with a double whammy: Smoking on start up AND oil in the carb.
cry.gif



When I still had the L head briggs, I had this same problem. Thankfully the new toro has the carb and the breather tube on the same side so tipping it to the opposite side has no ill effects, I just cant tip it upside down I guess, lol.
 
Originally Posted By: Bluestream
You've done 4. Oil changes on a one year old mower???seems overkill

Well at least I have a valid excuse as to why I'm in the forth season without a OC on my mower, SOHC has taken my allocation...
 
Originally Posted By: TFB1
Originally Posted By: Bluestream
You've done 4. Oil changes on a one year old mower???seems overkill

Well at least I have a valid excuse as to why I'm in the forth season without a OC on my mower, SOHC has taken my allocation...


I don't mind sharing, I only have 3/4 of the gallon of T5 left. That should get me through about three more years of 4x oil changes for a total of 16ish? Plenty to go around...
 
I got this freebee Honda engine at seven years old & 99% it had never seen a change(probably added to after incorrect tilting), figure with a change at 3½ years it'll think it's something special... I did run it for a couple months on Advance 10w-40 as a flush prior to changing to the M1 0W-40 that's still in it... Next change will also be 0w-40 M1, no I won't flush it again...
 
I'm only flushing mine to get out the run-in debris. even after three changes it still had little chunks and metal fuzz up under the valve cover. I wiped them out with a lint free cloth while checking the valve lash for the first time.

I am guessing the wear metal was still up there due to not getting much oil splash/flow to carry them to the sump.
 
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