13 replies to this topic

[KennyP]

The guy I have worked the remodeling with the last few years asked me to look at his push mower. It had a knock and was burning oil. It was a Craftsman mower with a B&S engine. I fired it up and the knock wasn't the rod. Pulled the plug and found lots of carbon build up. Decided to tear it down to see what was going on. Sorry for no pics, dummy me. But what I found was the lower oil ring had come out of the slot and had been wedged between the piston and cylinder. It had been this way for some time. Then I looked at the engine #'s to see what parts might cost to fix it. Saw the engine DOM was March 2010. I called him to find out when he bought the mower, that was July, 2010. Called B&S customer service to see what warranty might still be on it. Found out 2 years on manufacturing defect. So he got hold of Sears. The mower is on the way to Texas for them to look over. Hopefully they will fix him up. If I had realized it was that new to start with, I wouldn't have taken it apart.
Anyway, I have never ran into this kind of problem with an engine before. The only way I can see that oil ring coming out of the piston slot had to have been when they installed it at the factory. Dummy me for not taking pics! This is an aluminum cylinder and is wore/gouged where the ring got into it. New piston was $47, plus a bore might not clean it up.

[JDBrian]

That's a strange problem for sure. Are the engine bores Aluminium without any liner? That's not going to have a very long service life anyway. I imagine he'll end up with a new engine or an entirely new mower. Many people forget about warranties and sometimes can't even remember how old something is. I find as I get older I can't always remember when I bought something. I was cleaning out the car glove box the other day after changing the cabin air filter which is conveniently located behind the glove box which is secured with 9 screws. I wanted to find a receipt for the summer tires on the car because they are not wearing well. i could have sworn I bought them in 2011 but it was Sept. 2009. So I can understand how your customer would not remember about a warranty!

[KennyP]

They bore looked all aluminum to me! I didn't peel the head gasket from the block, but saw no change in metal color. Not sure what HP was supposed to be, only had 5.5 ft. lbs. torque on the cover. Could have been 55, didn't look too close. Sure started easily, though.

[MH81]

Weird that it ran that long with it like that.
Interesting.

[DougT]

That is a strange problem. I'd have thought if the ring was stuck between the piston and cylinder when it was new it would have been a bear to turn over.

[NUTNDUN]

Sounds like a defect in the aluminum block making it softer then normal and allowing the ring to chew in to it. I could be way off though LOL.

[KennyP]

Weird that it ran that long with it like that.
Interesting.

I think he last used it last fall. I have had it for a while this spring, just hadn't gotten to it till yesterday. Didn't realize it was that new of a mower.
George, that ring wedged between the cylinder and the piston was harder than either. Something was going to give which turned out to be both the piston and bore.

[JD DANNELS]

That is really weird! I would not have thought there woud be enough clearance for a ring to wedge between the piston and cylinder?
Guess it just goes to show anything is possible.

[HDWildBill]

It amazes me how many people will tell me to go ahead and fix something when it is still under warranty. I had a Cub Cadet push mower come in with the complaint of no power. It failed Compression check and Cylinder bleed down both test's and still had another year and half on warranty. We ended up getting a donor engine.

I have a good friend who had a curved shaft weed eater that the bottom bushing would heat up after a few minutes of use, it ended up finally burning up and seizing. It was only a few months old but she just flat refused to take it back said she didn't want to deal with it. I hope everything works out for your friend.

[KennyP]

Well, Sears is pitching a B***h be cause I took it apart. My friend said no problem, I'll just go to small claims court. AND HE WILL!

[Texas Deere and Horse]

B & S small hp engines, 1 1/2 up to 5 hp were built without a cast iron liner for years. We used to race 5 hp Briggs engine and were very happy when we discovered the I/C Briggs block with the cast iron liner.

[caseguy]

It's weird that you would make this discovery now Kenny. Just a couple of days ago, one of my co-workers came in to work and said that he's replacing the rings in his four wheeler because the bottom oil keeper came out of it's groove and made a mess in the cylinder. I think it's a Honda, but I'm not sure. Cheaper materials, outsourced assembly, limited lifetime planned replacement engines! How lucky we are to live in such an age!

[Toolpartzman]

Interesting alright. My 2 cents. I'm assuming only a portion (rather than the entire circumference) of the ring was out of the groove. One culprit might be a mis-matched ring during assembly or a poorly manufactured ring. I agree with JD that the piston-to-cylinder gap normaly would be much less than the difference in ring ID/OD normally. Wrong piston assy also or overbore might also be a possible culprit. Wrong piston assy (for smaller bore engine)might run a short while when new since the rings seal radially on their OD with just a minimum of the ring actually in the groove, then with just the slightest wear (cyl or ring) the ring escapes the groove, and starts beating up the whole enchillada,

Edited by Toolpartzman, May 26, 2012 - 06:44 AM.

[KennyP]

Since I didn't take pics, it's hard to explain. But it looked to me like they let it slip out of the compressor when installing and forced the piston on into the hole. Sears has taken the whole thing for evaluation, so hopefully he will get a new one soon. There was a very worn spot just below the groove for it, plus the metal had been forced into the groove pinning the other ring and expander at that point. Cylinder wall had a very worn spot where this had been. Bad enough I could feel it just running my fingers around in there.