Lawn mower engine smoking. Tilted wrong way.

April 3, 2005 9:46 AM

I tilted the lawn mower the "wrong" way (which is to say not with the spark plug pointing up) in order to clean the underside, and now when I start it up, the engine pours out lots of white smoke. This seems to be because some part of the engine has been flooded by gasoline and/or oil (because, I guess, this is some super crappy engineering). Anyone know how to get this to stop? Do I just need to wait for it to dry out? Is the solution somehow spark plug-related (the manual seems to imply that removing the spark plug is necessary to every single bit of maintenance)? Will the engine simply smoke until all the oil is burned off? Am I going to blow up my lawn mower?
posted by bryanjbusch to home & garden (14 answers total)

It'll smoke until the oil that drained from the crankcase into the combustion chamber is burned off. It won't blow up.
posted by fixedgear at 9:57 AM on April 3, 2005

How come all of the piston action (and associated vacuum effects) wouldn't have flooded the combustion chamber with oil with the engine on, yet turning the mower upside down drenches it?
posted by rolypolyman at 10:03 AM on April 3, 2005

What fixedgear said.
BTW, all you need to do is take the ignition wire off the plug tip.
You may burn enough oil to mung up the spark plug (you'll know if the mower chronically won't rev up the way it did, or sputter. etc). No worries - get another plug and a gapping tool to make sure it's set right before you replace.
posted by nj_subgenius at 11:36 AM on April 3, 2005

White smoke: oil
Black smoke: too much gas

If the plug gets oil-fouled and makes the engine run badly, remove it and clean it or replace it. You'll need a spark plug socket.

rolypoly - when the engine is running, the oil is in the bottom of the crankcase, with a bunch of air on top. The piston rings are supposed to seal the combustion chamber from the crankcase, and when the engine's running, they do an adequate job. If you turn the engine upside down, though, the oil sits on the bottom of the piston and eventually seeps past the rings and into the combustion chamber.

nj_sub - what would taking the plug wire off accomplish?
posted by Kirth Gerson at 12:13 PM on April 3, 2005

Rolypolyman: Single cylinder four stroke engine is pretty simple. There is no oil pump, the engine is lubricated by oil being flung from the rotating crankshaft onto the cylinder walls. In normal operation, the piston rings are scraping the cylinder wall clean on every downstroke, and very little or no oil gets by them and ito the combustion chamber. When the engine is turned upside down while not running, oil can seep by the rings and into the combustion chamber. The vacuum effect is happening above the piston, not below it. When the piston goes from top dead center to bottom dead center, it creates vacuum. That is what draws the fuel/air mixture into the combustion chamber.
posted by fixedgear at 12:15 PM on April 3, 2005

Gas lawnmowers pollute as much as the worst-offending big-rigs you see belching plumes of black smoke. It's really quite disgusting.

You may wish to look for an alternative: a reel mower.

These aren't your grandfather's mower. With precision ball bearings, better weight distribution, etc., they're a breeze to use. Indeed, arguably less work than pushing a heavy gas mower.

Also, they're better for your lawn: the blades slice the grass instead of relentlessly bashing it into compliance.
posted by five fresh fish at 12:47 PM on April 3, 2005

i tried reel mowers for a small trailer park sized lot ... they do not cut as well and do not bear up well over the years ... the problem is the cheaper ones, at least are not that sturdy

any one would be insane to use one for a large lawn

i've had the white smoke problem many times ... it goes away after a couple of minutes
posted by pyramid termite at 1:58 PM on April 3, 2005

electric is fun. Like pushing a box fan around the yard.
posted by petebest at 3:16 PM on April 3, 2005

I use a reel mower on a suburban sized yard (it's not a zero lot line but it's not huge either). It works fine. It's not appreciably harder to push than a "regular" mower, probably because it's a lot lighter (I can pick it up with one hand). My wife, however, can't push it. She can't seem to get the hang of how to push it. And that's a problem for some people. You need to be a bit above it, pushing down, and not behind it, pusing forward, at least with my mower, or the front of it will lift up a bit, and the wheels will not contact the ground well, and the wheels turn the blade. So the blade stops turning, the grass gets stuck, etc. For my mower the cause of this is that there are some smaller supprt wheels in back.

Anyway, I've convinced several people in my office to use one, based on trying mine out. I bought one from, I think, American Lawnmower Company, for perhaps $80-100. My only bitch is that I'd like a wider one.
posted by RustyBrooks at 3:55 PM on April 3, 2005

Reel mowers cut better than gas or electric mowers.

Reel mowers are like scissors. Rotary motors are like food processors. The former cuts; the latter tears or smashes (depending on how sharp the blade is).

If you had problems with your reel mower, it is because it was incorrectly set.

Reel mowers weigh significantly less than rotary mowers, so there is less effort required to push it.

You do, however, need to purchase a quality reel mower. However, a good reel mower is far cheaper than a good rotary mower.
posted by five fresh fish at 4:47 PM on April 3, 2005

Your past this stage already design8r but as a warning to others you should let the engine sit for a bit after tipping over to let the oil drain back if it did get into cylinder.

If you want proof of five fresh fish's statement take a look at what anyone who cares about their grass (golf courses, ball diamonds) uses. Reels all the way.
posted by Mitheral at 10:06 PM on April 3, 2005

In my experience, reel mowers work fine if you have a lawn in decent shape - fairly smooth, even grass, smallish in size - but on my neglected, crab grass infested, pockmarked mess a reel mower just doesn't cut it, literally and figuratively.
posted by madajb at 2:45 AM on April 4, 2005

You remove the plug wire so it can't possibly fire with your hand in there. Don't leave the wire hanging where it could flop onto the plug, stick a dab of electrical tape ove the business end of the wire.
posted by unrepentanthippie at 5:00 AM on April 4, 2005

I should mention that in addition to not polluting, reel mowers reduce water usage: cut grass does not lose as much water, nor require as much water in repairing itself, as torn grass.

Also, it's a good idea to let the grass cuttings go back into the lawn. They're a good source of organic nitrogen, and reduce the chemical load on your lawn.

Myself, I'm transitioning my yard from lawn to something more environment-friendly. Think I'll use rock on the lower, steep-hill side of the lot, which is a bugger to mow at any rate; and perhaps do some terracing and natural grasses on the upper side.

On the whole, lawns are a Bad Thing. Way too much water use, nasty chemical fertilizers, nastier herbicides and pesticides, and terrible two-cycle engine pollution from the mowers.
posted by five fresh fish at 8:57 AM on April 4, 2005