Lawn Mower Problems

[lowpolyjoe]

Last weekend I was mowing the lawn in this terrible hot and humid weather we've been having.  I was finishing up on the last part of my lawn when I hit either a root or small clump of dirt.  It stalled the mower and it looked like a little smoke came out of the exhaust.  I was unable to start the mower after that.  I was shot from the heat and just put it in the shed until today. 

This afternoon I am able to start the mower but it seems like it's running kind of rough and there's definitely white smoke coming out the exhaust. 

It's ~2 year old Craftsman push mower.  I don't have the model number on hand, but it's something similar to this, just to give you an idea:

http://www.sears.com/craftsman-21inch-rear-bag-push-mower/p-07137430000P?sid=IDx01192011x000001&gclid=CjwKEAjwiru9BRDwyKmR08L3iS0SJABN8T4v2ZWjZM57DgzJdUuWLzdhV00AVL1uW5ccKAxOXz-SmxoCjr3w_wcB&gclsrc=aw.ds

Anyone hazard a guess at the problem?  I don't know much about engines but white smoke is burning oil, right?  Any chance it's something as simple as a gasket that I could replace myself?   Aggravating that I killed a new(ish) mower.   If a new one is $200 I wonder if it's even worth bringing it to a shop for repair if they're going to have to crack open the engine and replace something significant?  I've never been to any of the shops around my area but there's a lot of landscapers and rich folk around here so I expect the average joe like myself isn't gonna get a great deal on repairs

[Ljohnsaw]

Well, that's odd.  If it wasn't for the smoke, I'd say you possibly partially sheared the shaft key on the flywheel.  That would put the timing off a little on the magneto making it hard to start and/or rough running.  Did you happen to put your 2-cycle gas in the tank by mistake?  That could lead to the smoke.

If you pull the cover off (pull start), and take the large nut and washer off, you might be able to see the key way in the shaft and the flywheel.  If they are out of alignment, time to replace the key.

[DelawhereJoe]

If your blowing smoke sounds like it damaged the rings coming to a dead stop like that. Try pulling the breather line that leads into the carb, I have an old 3.5 hp mower that smokes so much it will choke itself out if the breather line is connected to the carb. It too came to a sudden stop from a hidden root.

[lowpolyjoe]

Thanks for the advice guys.

It's not likely 2cycle gas.  I had mowed 90% of my lawn last weekend on this tank of gas with no issue.  I will mention that the lawn was very tall and a bit wet and it was stressing the motor some before this incident

I said 'push mower' to distinguish from a ride-on, but I should have said 'self propelled'.  Looking closer, a comparable replacement is more like $350 than $200 so I may have to dig into this mystery a little deeper.

The little I know about engines, I was thinking if the engine came to a dead stop at a bad time during the combustion cycle it could cause all sorts of trouble.  What level of difficulty are piston rings as a DIY project?  I don't have much engine experience but like to tinker and I'm too cheap to go to a shop.   :D

I'm busy today but maybe tomorrow i'll do a little looking around

[Kbeitz]

Did you tilt your mower looking for problems ?
Maybe you oil soaked your air filter...

[thecfarm]

Just a guessing. I buy the chaepest lawn mower I can get my hands,usally walmart,use to $100 now,there're $140. I call them my mini push hogs.  ;D If I get a year out of one,I'm doing good. I stall mine ALOT. Once in while a shear pin will do it in. When you start it,does it try to tear your arm off? Most times mine won't start and I replace the pin and I'm off and going. Most times I am mowing stuff 2 feet tall.Good luck.

[Kbeitz]

Just a guessing. I buy the chaepest lawn mower I can get my hands,usally walmart,use to $100 now,there're $140. I call them my mini push hogs.  ;D If I get a year out of one,I'm doing good. I stall mine ALOT. Once in while a shear pin will do it in. When you start it,does it try to tear your arm off? Most times mine won't start and I replace the pin and I'm off and going. Most times I am mowing stuff 2 feet tall.Good luck.

That funney... I still have my same push mower now for 46 years.
Guess that just don't build them like they used to...



 

[thecfarm]

What's that flat green area you have there?? My mini bush hogs don't see areas like that. I said stuff 2 feet tall,meaning bushes,not just grass. I even cut out the support on the bottom of the discharge,on one of those lawn mowers. That way I could move it sideways and chew off some of the bigger bushes. Than it tried to fold in half on me because it needed that support,so I bolted a piece of channel iron across it. Made it nice and rigid. Can't understand why it did not last long.  :D This is some of my claim back pasture idea. I am falling behind on the reclaiming part. I have one area that really needs a dozer. VERY uneven,won't talk about the rocks.

[21incher]

When my wife and I purchased our first house I bought a brand new $300.00 Jacobsen self propelled aluminum deck mower. She decided to try it out first on the slightly overgrown front yard. About 1/2 hour later I hear a bang and it stops running. She comes up the driveway pushing it with the blade in 1 hand and tells me it fell off and she needed me to put it back on. The only problem was about 2 inches of the crankshaft was still attached to the blade. Turned out the cap for the town water valve was sticking up in the grass and she never saw it. I then went to kmart and bought a $89.00 one that lasted 15 years.

[caveman]

There are others on the forum who can guide you to a repair of your mower much better than I would be able to.

For those of you pushing small wheeled mowers through tall brush, grass, there is a better way.  I have several old Kee mowers.  They were made in Samoset, Florida.  They have 20" heavy duty bicycle wheels and tires in the back and small wheels in the front.  The ones I have range from 20", 22", and 25" blades.  The engine sizes range from 5hp to 7hp.  They run horizontal shaft engines and are belt driven.  You can find them that are self propelled but they push so easily that that feature is unnecessary.  These mowers do a great job on lawns but will cut the heavy stuff almost as well as a bush hog.  Other manufactures have made similar products (Sarlo comes to mind) but they are not the same animal.  The decks of the Kee's are aluminum and some of mine have some small pieces broken out due to extreme use.
Caveman

[Jeff]

I have a hate hate relationship with lawn mowers of the riding kind. It seems I can not mow a lawn lately without having some sort of incident. Mowing the day before the pigroast I somehow hit a flush old stump I had been Mowing over for 2 years. It busted all kinds of things in the deck. Magic man was just arriving as I was dejectedly walking towards it with a 4 lb hammer to what must have looked like to finnish it off

[Hilltop366]

Did you tilt your mower looking for problems ?
Maybe you oil soaked your air filter...

x2  Check the air filter, if you tip the mower on the filter side it will often get oil on it, most are paper and would need to be replaced to fix.

[lowpolyjoe]

I was briefly hopeful that a few of you mentioning the "oil-in-the filter" would be correct.  I watched a youtube video where the guy described that issue and ran the mower for a while and the smoke cleared.


This morning I topped off the slightly low oil level in my mower and started it up.  Within 30 seconds there was smoke coming out the exhaust and then I started seeing oil dripping from the muffler  :-\

I been watching a lot of videos the last 24 hours on tearing down engines.  I went on a youtube bender a while back when trying to fix a power washer engine.  That didn't go well but at least I got to see the inside of an engine in person. 

I'm wondering if there's any chance I can fix this.  I'm 50/50 on whether I bother giving it a shot.  I might just stay in the air conditioning and order a new one  :(

[North River Energy]

Replace the partially sheared flywheel key, and make sure you torque the crank bolt properly so the key can do it's job the next time you hit something not grass.

[lowpolyjoe]

I didn't get a good pic of the flywheel bolt and key while they were assembled, but I didn't think they looked damaged.

The slot is not damaged that I can see




This pic of the key is probably useless, but here you go




I'm not a doctor, but I don't think this is supposed to look like this:




So this is where I'm at





Would blown rings do this?  The mower has only seen about 2 1/2 seasons so I'm pretty aggravated that it's such a mess.  My previous mower (also a craftsman) was left to me by the previous house owner.  I used it maybe 6 or 7 years and he must have had a few years into it already.  My wife surprised me with this new mower because I complained a few times that the old one was sometimes tough to start.   My neighbor took it out of my trash and it's still going for him.  I didn't even take very good care of it.  I know I hit my fair share of stumps and berms with it.  They really don't make em like they used to.

[Kbeitz]

Yes broken rings will let compression past the piston putting
pressure in your crankcase pushing oil out the breather tube
into the carb. Also you could have a blocked breather drain hole.

[lowpolyjoe]

Got the piston out.   I thought it would be obvious to me if the rings were bad but I couldn't really tell.  They were very loose, but perhaps that's normal?  if I push against one side, there's a visible gap on the other side seen on the right here



I can just push the split part of the ring right out of the gap with no effort.  Is that expected?



I didn't take the oiler ring stuff out, but here are the top 2 rings



Cylinder shows some marks but I can't feel any with my finger or catch any with my nail.





The same cannot be said for the piston.  These gauges are fairly deep and easily felt and caught with my nail.  But does that matter since the damage is below all the rings?






Unless I'm mistaking the color, it looks like there is carbon everywhere.  I believe this is the exhaust. 






I wanted to take the valves out and have a look at them, but it looks like the only access is through the little cover shown in the bottom of the last picture.  That appears to require mangling the folded metal seam.  I'm holding off for now. 


Does it look like those rings are bad?  does the piston need to be replaced due to those tracks?  If I replace these parts, I assume I have to get all this carbon off everything and all new gaskets.  I haven't looked up parts prices yet.  I'm almost hoping everything is really expensive so I can just throw everything in the trash and buy a new mower  :D

[North River Energy]

It doesn't take much to tweak that aluminum key, and if that happens the ignition timing is changed. (The key should have a plain aluminum finish, without any sign of lines running down opposites sides). So, the motor still pulls in the same amount of fuel on the intake stroke, but it won't burn all of it on the combustion stroke. The excess goes out the exhaust, and the motor will run 'lumpy'.

But at least now you know what the inside of that particular engine looks like. ;D

Your engine was running fine, and then it wasn't. Wear on the piston, rings, etc, will lead to gradual performance loss, not sudden failure as you describe.

[lowpolyjoe]

I took a closer look and there is a little score line on one side of the key.  But it seems awful minor to have any impact on the timing?



Lets say the key is the problem, I get a new key and I reassembly everything...  I still have to get the carbon off everything, right?

[Den Socling]

When I have a problem with small engines, I look for a foam air filter. Rinsing them with gas can make a world of difference.

[DanG]

This has sounded like a spun connecting rod bearing from the start to me. I'm really not sure a repair is worth the time and money. I would look around(Craigslist) for a used rider if it were me.  ;)

[North River Energy]

You've got it apart, so you might as well give it at least a rudimentary cleaning.
Lawnmower engines are not precision instruments, so don't get too obsessive.

And yes, that's enough deformation on the key to make a difference.

I had a Honda generator seize for lack of oil once (oops...). It happened on a Saturday, and I really wanted to finish the job, so I tore it down, smoothed the ragged con rod bearing with a razor blade and lobster pick, and put it back together.
The crank was not damaged, most likely on account of using synthetic oil.

Started on the first pull, though it smoked like a dragon. It's in the repair queue, but has seen at least another 60 hours or so without additional attention other than frequently topping off the oil.

[Kbeitz]

Your key is fine...
Remove this cover and check the oil drain hole...



 

Check out the engine link...

http://www.mytractorforum.com/44-small-engines-repair/567810-briggs-breather-blowing-oil.html

[mburrow]

it looks like the piston has a chip out below the oil rings.
if so it will need a new piston

[Rural]

Before getting into a major tear down check the crankcase breather, there will be a small rubber hose from a little valve assembly on the side of the motor to somewhere close to the carb. Remove the assembly and give it a shake, it should rattle as there is a valve inside that slows the crankcase to vent, if stuck it will build up pressure in crankcase and force oil up around piston. Give it a good wash out with a little gas and try it again.
If it does not work then you do indeed probably have a busted ring!

Edit - sorry I see you already have it torn apart, check the breather valve anyway, if not I dont see any thing else obvious, the black build up MAY be just from the oil burning if run for any length of time but more probably from worn or broken oil control ring.