Push Mower Engine Question (Husqvarna)

[leehljp]

I have a 10 year old Husqvarna 21" push mower with Honda engine. Still cranks on the first pull (most of the time) but a rare occasion needs a second pull. I have never had a push mower in this great of overall shape after 10 years of use.

I am having one problem that has me worried a bit. It runs fine when cranking and for about 2 or 3 minutes - then it starts smoking out the exhaust (medium to light) and continues for about 5 to 10 minutes - and then the smoking stops. The yard is flat, so the mower stays level.
• It started smoking like this last summer.
• It is not over filled with oil. I change it every spring and use recommended weight in synthetic oil.
• I have changed plugs about every 3 years.
• I change filters yearly.

I have two thoughts:
1. an oil ring problem but I don't know if lawn mowers, even Hondas have Oil rings.
IF it is an oil ring, where do I get oil rings for a Honda. I had enough trouble finding out that it had a Honda engine. Now to chased down the parts. I haven't overhauled a gas engine in almost 50 years. But I could still do it if I had to.
I remember engine mechanics speaking of "sticking" oil rings but never encountered that myself, so I don't know exactly what that means or how to fix it except to put a new one in - in the fall, if I do. Opinions? It has been a while since I did this type of mechanical overhaul.

2. It seems like one of those crankcase to throttle body "valves" that reroutes crankcase smoke to be burned. Only it is moving some oil into the carb for a few minutes, or the valve is sticking, if it has one.

Any ideas?

I hope this mower stays around as long as my year 2000 Craftsman 42", which is still going strong.

[capncarl]

What oil are you using?

[cwsmith]

First let me state that I am not an engine mechanic, but I've been mowing lawns since I was about twelve years old and I've always used Briggs and Stratton engines, except for one time when my Dad had bought a Tecumseh. So, I've been using a push mower for about 76 years; and that includes changing the oil, spark plug, blade, parts, etc.

Did Honda recommend 'synthetic' oil? Do you check the oil level before every start-up?

I don't use synthetic oil either in my car or the lawnmower. My current lawn mower is a Craftsman which my son left me when he moved out to Iowa about ten years ago. I think it's about sixteen years old now. Like yours, it starts on the first pull about 98% of the time, even after sitting for the winter.

About the only thing I can think of that would cause consistent smoke would be if the rings are going, or whatever your particular engine uses. Check your parts lists illustration that in your owners manual. Smoke only occurs if oil is excessive in the cylinder. A worn or cracked ring will do that or if you've tipped the mower on it's side during service or storage. In the latter case, smoke would occur, but burn off quickly.

I had a neighbor who apparentlly rarely checked their oil level and had run the engine with little or no oil in it. That ruined the rings and they no longer sealed the piston against the cylinder wall, thus allowing oil to seep into the compression area where it burnt and cause it to smoke profusely.

Oil generally does not break down unless an engine is run at a destructively high heat situation (like failed cooling). On an air-cooled engine like with a lawnmower, you just need to keep the fins clean. Engine oil mostly needs to be changed regularly because it gets dirty. When I check the oil level, if it starts to get dark, it's time to change it, and from my experience if it's not dirty, it's a waste to change it, at least in the lawn mower. On the other hand, I change oil every 3,000 miles on my cars, but there I use very basic, cheap oil and no synthetics at all. Again, the oil doesn't breakdown, it gets dirty. So I change the oil and the oil filter. The old oil gets recycled, which basically means they clean it.

When we bought our first home, way back in 1970 I needed a mower. My FIL was the Sears hardware manager and he offered me a good deal on a Craftmand 'Eager One' mower. It was close to $90 which at the time was not affordable to me. That weekend, a local drugstore had a sale and I bought a Briggs & Stratton-engined mower for $29. My FIL understood but told me I'd probably have to replace it in a year or two. I had that mower for thirty years and every Spring would go through the ritual of 'first start', and it would do so on the first pull! I dumped it only because the pan was rusted and one off engine mounting bolts fell out. I've only owned five lawn mowers in my 79 years, and that counted the one I left at the house in Painted Post when I sold it two years ago. (One of those I broke when I hit a city water valve, it bent the crank shaft and punctured the case!)

Good luck and let us know what you discover.

CWS

[capncarl]

I’ve had most everything that Honda has manufactured except an outboard motor. My wife’s 1986 Honda lawn tractor, liquid cooled 2 cylinder in-line overhead cam engine with shaft drive still runs great, it’s been completely under water 2 times! My 1000 watt Honda generator does exactly like you describe, smokes until it warms up. This generator was previously used by a co-worker that was heavy into drag racing and someone used it every weekend, I would be scared to guess the hours on it, but it probably be in years rather than hours. It is worn out! I changed the oil to a synthetic 20w50 synthetic ( I think it was Amsol) manufactured for vTwin motorcycle engines. Expensive, but your get 5 changes per gallon. The smoking did not completely go away but it is barely noticeable and no smoking is noticed after it gets warmed up. During our power outage caused by hurricane Michael I loaned it to a cousin to keep his freezer and refrigerator operating. They used it non stop for 2 weeks, never turned it off, just let it run out of gas, refill it, check the oil and start it back up. The last day of the power outage they called and said the generator died, still ran but wouldn’t make electricity. That didn’t suprise me, I figured it was running on borrowed time, then they told me that every day they had used it to power their coffee maker and griddle without even unplugging it from the freezer and refrigerator. It really shouldn’t have powered up the refrigerator and freezer at the same time, much less the coffee maker or griddle. When I got it home I checked the tiny little circuit breaker and found it tripped. Works great now! These air cooled engines run hot and need a good oil. After they get worn they need a better oil.

[leehljp]

Thanks fellows for the input. Capncarl, I use 10W30 Mobile1. I might give the 10w40 or 10w50 a try. Like you, I buy a gallon at Walmart and use it in both the craftsman LT1000 and the Husqvarna 21" - until I run out. It is about time for another gallon.

I don't think it has ever gotten near empty in oil. I always check it before starting - every time. Just a habit. I am going to change the weight of the oil and see if that changes anything. I really don't want to get into the rings and my hesitancy is more of plain procrastination than not knowing what to do. Once I get started . . . I can fix it.

[capncarl]

These small air cooled engines are all aluminum and usually don’t have steel cylinder sleeves. From my observation, I haven’t read about it anywhere, but, the piston must have a bit of wobble at the bottom of the stroke and wears the cylinder there, thus when the engine is cold the rings can pick up oil. When it warms up the rings tighten up and don’t pick up as much oil. I’d go ahead and step up to w50, it will not hurt and save you some trial time.
Years ago I had a single cylinder Gravely garden tractor that I filled up with 90 wt gear lube after it was covered with water for several days during a flood. Several years later I started it up and used it for 10 years, I had forgotten that it had 90 wt. in it, and only used it 10 hrs each year. I checked it every cranking and it looked like honey so why change it.

[capncarl]

leehljip, funny how things happen that jog your memory. I’ll write it down before I forget it. I have worked on a number of Go Cart, Lawnmower and tiller B&S, Tecumseh, Wisconsin and Honda engines. The PCV hose and screen would get clogged up with dirt, oil sludge and debris and cause all manner of problems that were difficult to diagnose, usually excessive oil burning at start up. Vertical shaft engines would also leak through the lower main oil seal. Replacement or a good cleaning usually fixed or helped the problem. B&S and Tecumseh had a small removable plate under the intake and exhaust ports with a hose going to the air cleaner, and Honda had something similar. Older engines had blow by on the piston due to wear and would pressurize the crankcase if the pcv screens and hose was dirty and expel a fair amount of oil into the air filter box and force oil past the rings.

[leehljp]

PVC hose and screen - I need to get in, find it and clean it. It is hidden but I am sure it has one.

[capncarl]

Ebay the Honda model #. Easier than explaining to the parts clerk.