Lawn Mower White Smoke
 

Hey folks,

I was cutting my lawn this weekend. About half way through, after emptying the bag, I pulled the cord and was welcomed with a plume of white smoke which reduced itself after 20 sec to a faint but steady output of white smoke.
Mower ran fine except for the smoke. Sopped for a couple minutes, restarted, same deal.

Ok, oil burning in the cyl (4 stroke engine)
'
If had it temporarily smoke after running over some dips and valleys on my property, splashing oil into the cylinder and such. But it went away after 15 seconds.
Oil level was is reading as full
Packed it in for the day.

Started it this afternoon. Zero smoke at startup, but after 10 seconds of running, the faint steady smoke began to appear so I shut it off again.

Only 1.5 years old, Briggs and Stratton motor -- still under warranty, thankfully.

Thoughts?

Beginning of a head gasket leak?
Breather clogged?
cracked head or block?
ring issue?

Thanks

Perhaps some carbon on the intake valve, derf? For some reason, some oil is definitely getting into the cylinder. I'd try a little Seafoam in the gas tank to see if that helps. Maybe an ounce or two based on what HP Briggs it is. Someone else may have a better suggestion.

Thanks, Rube.

I find it interesting that there is zero smoke at startup. It is an OHV engine, so if oil was leaking past the valve guide seal I would think it would start burning oil as soon as the motor got up to speed, since it is a splash type oil distribution system.
I also find it difficult but not impossible for the head gasket to be failing, as cooling down should not make it seal again, although if it is a miniscule leak, I guess the thermal expansion of the metals would open iup the seal as the mower heats up.
It runs fine so it has good compression (I assume), though if the head gasket leak was slight, I might not see it in a compression test -- dunno, plus I don't know what the beginning compression for these engines is, though I could look it up.
Suppose it could be a ring issue, but that would lead to reduced compression which does not seem to be an issue

I fear it is a hairline crack in the head or block that, as the engine warms, opens up to a fixed separation at a given temperature, thus a fixed amount of oil is getting into the cylinder per unit time.

I need to go out and see if I smell gas in the oil and vice versa.

Don't know where the breather is but I assume it vents crankcase pressure just like an always open PCV -- will look into it more.

Had dream last night I was cutting with it and hit a bump and turned upside down and a car head gasket milkshake poured out of the unit. Not possible here but tells you where my subconscious is.

Air filter is dry for now.

Cross posted.

Air cleaner is dry.

Float sticking would dump gas into the oil, yes? Thereby overflowing the mixture into the cyl?

I will go smell oil for gas and report back.

I have a 20 year old snowblower and a 22 year old mower, both craftsman w briggs n strattons -- neither has ever let me down, even with abusively long oil change intervals.
MAkes ya wonder.

What makes the float stick? Varnish? I use Stabil on every drop of gas thatgoes into my gas powered equipment and have for 22 years. Never 1 problem sarting up next season without drain. Plus stabil fights varnish formation, so even stored with gas in it, it's not running while stored so shouldn't make any difference. So far my longest preserved gas that still works is 2 years. Haven't tried past that. Also use ethanol<10% per mfr's recommendations.

Thanks

Oil doesn't smell right. Not burned. HINT of gas kinda sorta there, but that might be me willing it to be so in my mind.

We'll go with carb float stuck and pushing gas into oil and overflowing crankase oil into cylinder.

This is one of those "never need to change the oil" mowers where you supposedly add n go without ever doing a full change. Seems designed to trash your mower in 5 years so you have to buy a new one. I will change the oil but not until the warranty claim is over. Actually they will do it as part of the carb replacement.

Where do you acquire said petrol?

It is available at at least one station in every town here. We have many lakes and the boats run much better on ethanol free fuel. It may be an Oregon thing.

No, it's everywhere. I hear rumors that I've never chased down. I was wondering if it would be more likely to be found at a station that sells the 100 octane stuff,......
Dropped off lawn mower today for a warranty claim.

A Husqvarna 21" AWD w the bigger back wheels does NOT fit in the trunk of a 97 SC2

But it does fit on the front seat w the back laid down

If you have a Sunoco station there, check it, derf. That's the predominant station that sells the good stuff here. The local boat dock here is selling it for $4.35 per gallon!!!!

Thanks, guys!

In for warranty claim at Briggs and Stratton authorized service center. Should get to it this week. Dude said he smelled no gas in the oil nor did it smell burnt. Air cleaner is dry so breather likely ok and carb float probably stuck.

That leaves head gasket, cracked block, and cracked head. It is not overfilled with oil and I was emptying the bag when it went down. It only smokes after 10 seconds of running and puffs a constant reproducible amount of smokes on each firing while running quite smoothly.

My guess is head gasket just starting to fail or hairline crack in head, neither of which come into play until they begin to heat up and the surfaces separate from thermal expansion

Bones,

no eco-mods?

(Sigh)

Just when you think you know a guy he wants to hot rod your mower but ignores aerodynamics

Verdict is the following.

Slight bit of oil on the air cleaner was getting sucked into the cylinder. How did it get there? Oil slosh while mowing the edge of my property which has a hump at the property line and a bunch of deep divots that the front wheels get into and bottom out, then pop out of. It's been 5 years I've been cutting my lawn with two different mowers, 2 years with this one and this has never happened before. Guess I'll have to slow down and keep a few spare air cleaners around. Never thought to take it off to troubleshoot, but even if I had, I would have thought it was a crankcase pressure issue pushing oil into the air intake just like excessive blowby in a car engine. I've never had to troubleshoot a small engine before other than when I tipped over my pressure washer when it slipped off the table it was on while I was working on it. Not surprisingly, the cylinder filled with oil. However the air cleaner did not get any oil on it. Whatever. Also found out that when extremely hot other, stopping for too long resulted in too weak or no spark and and a no fire condition. I always assumed this was the signature of a magneto issue, but when my current mower was checked, he said the plug was the issue, not the magneto, and the plug was beginning to gas foul from the weak spark. Put them together and the thing won't run. I assume you tell the difference by putting a new plug interested in a while hot or heating the existing one with a heat gun until it fails. Same deal for the magneto.

Now on to my beloved 22 yr old craftsman weed whacker. 2 cycle. New carb, new
fuel lines new fuel filter, primer bulb failed AFTER that. Can't get the thing to idle unless it is racing and the fuel filter seems to want to float which I assume means there is air trapped in it. Also I think the gasket between the carb and the rest of the unit has a slight tear in it and is letting unmetered air in, leaning out the mixture, thus requiring more fuel per unit time which eventually fouls the plug and it stops running. Then when I check for spark there is none, even after the plug is mostly dried off.
Shall I replace the gasket and plug and go from there? The carb has no mixture adjustment. The unit has only an idle adjustment screw, so everything else needs to be in order for the thing to run properly.

Am I headed in the right direction?

Double check the gasket, derf. Sometimes it's easy to put it in backwards. And double check your new fuel lines and make sure you got them routed properly. Sounds to me like maybe you put them on in reverse order and instead of pumping gas into the carb, you're pushing air into the tank. How do I know to check that? I've done it myself. That's why I still just replace one line at a time anymore. Also, if you nicked a small hole in one of the fuel lines, it can drive you nuts. As for the mower, I've never heard of such a thing. Just keep an eye on that thing for white smoke. Sounds to me like maybe they blew some up your tail pipe!!

No, it does happen with the OHV 4 strokes these days.

I can get it to run (weed whacker) and I have already figured out the lines are not on backwards by previously putting them on backwards. The mix is just all wrong.

I'll replace the gasket and plug. Then I will have replaced everything there is related to air spark and fuel.

Most common mix is 50:1 on the fuel.

I was referring to air:fuel, as it were.

It's 22 years old; if I didn't know to run it 40:1, we wouldn't be having this discussion.

Today I used it. 12 primer pushes, 10 pulls, 10 more primer pushes, 7 more pulls, starts on 8 (20th) pull, stutters on full choke, won't idle on 1/2 choke, toggle between the two to keep it running. Stalls. Full choke, 6 primer pushes, 4 pulls, starts on 5th. Stutters on full choke, runs on 1/2 choke for 30 sec, choke off, runs, stutters, 1/2 choke, stutters after 20 sec, stalls. 3 primer pushes, starts on 2nd pull, full choke (yes full choke) rotate 90 degrees around shaft axis, idle picks up and steadies because I sank the fuel filter on the side of the tank that is now down. Run 20 sec, doesn't stall, dare not touch the throttle, hold at 90 degrees for 5 min while I trim. Off switch making contact today, use it to turn off.

So you see, it's a bit more complex than they designed it, so semi normal operation is sought.