Piston Skirt Failure

[Bob95065]

I picked up a 1650 parts tractor from a Facebook ad that looks like it spent some not so quality time in a mud bog. The engine was seized when I got it.

I took the engine out of the tractor and put it on the bench. I drained the small amount of what looked like crude oil from the crankcase. I removed the head and pan. In the bottom of the pan I found a chunk of aluminum about the size of a quarter that ended up being from the piston skirt. I saw no other obvious signs of damage.

I used a block of 2x4 and a big hammer to persuade the piston down the bore. It got it to BDC and used the block and hammer on a con rod bolt to get it to TDC. Whatever was seized released and the engine spins freely now. The bore looks smooth with faint cross-hatching and no scores or scratches.

What could have caused the piston skirt to fail? Am I safe to start the engine as-is? I want to see if it burns oil or smokes before I buy a standard diameter piston for it. I wanted the engine for another tractor that has developed a smoking habit. I can use this one while I rebuild the other.

Thanks,

Bob

[Mike McKown]

Originally Posted by Bob95065

What could have caused the piston skirt to fail?
Bob

You want a guess?

I'd guess the rings rusted to the bore and stuck the piston. Someone tried to force the engine to turn over, kicked the piston sideways and broke a piece of the skirt off.

That guess is only good if the stuck engine and the broken skirt are related.

Can you run it? Depends. I broke a skirt off the piston in my 400 cc Suzuki MotoCross bike. Fell down in the crankcase and when the rod came around, it hit the broken piece and punched the bottom out of the crankcase. I glued the pieces back together on the crankcase and never looked back. Didn't seem to hurt the running any.

You may get lucky too.

PS. Probably not a good idea to run it if the skirt is broken off the thrust side of the piston but the only wat to tell is pull the pan.

[ol'George]

Ya you can run it and see if it blows up, if not
then run it till it soon does. your money not mine.
Me, I'd take it apart and see what it needs to repair it properly.
It is a 16 hp kohler, a good engine and worth what it costs to repair.
What it is not, is a cheap china predator clone/throwaway.

[Mike McKown]

If the rings were rusted to the bores to lock the piston, it likely won't run real well or real long anyway without service.

[Billy-O]

The other guess is the motor was just plain worn past "time to overhaul" point and the piston was just too sloppy loose breaking the skirt. Then is was parked because it smoked too much.

My opinion is no-go on running it until it is properly rebuilt.

[finsruskw]

Spend the money, do it or have it done right and it will serve you well for years.
Should be about $400 if you re-assemble it yourself.
Good luck!

[CADplans]

I had a 149 fail the piston exactly like that,,
The tractor had been used for field mowing of several acres when I first purchased my place, and I did not have a bigger tractor,,

The hard pull of mowing caused a high strain on the 14HP engine,,
that strain caused the piston to wear a "step" in the bottom of the cylinder travel,
finally, the step become large enough, that the step caught the skirt of the piston, and broke it off.

The rest of the bore was perfect, this machine had received a new long block just before I purchased it.

Well,, my fix was to use some 60 grit emery paper, and hand sand the step away.
I bought a new piston, installed it, and the tractor ran perfectly for another decade.

Look at the bore at the bottom of the piston travel.

[Bob95065]

Since I found the piece of the skirt when I took the pan off before I started tapping the piston it wasn't due to what I did. I also found the tab off the governor arm in the sludge. That may be why it was parked, who knows.

I am not looking to run this engine before putting a piston in it. I wanted to start it to see if I could get away with a standard piston for the time being. Sorry if I made it sound like I wanted to blow up a 16HP Kohler. I'll tear it down and take some bore measurements to determine a path forward. CADPlans, thanks for the explaination, I'll check the bottom of the bore for a step.

I've used Cub Cadets since 1986 and have rebuilt a few over the years. I posted because I've never seen this type of failure before. I'm trying to get this engine going for as little money I can to buy some time. I have another Quietline that developed a smoking habit. It's my main worker and this engine could be used in that frame to get me a few months.

[ol'George]

Originally Posted by Bob95065

Since I found the piece of the skirt when I took the pan off before I started tapping the piston it wasn't due to what I did. I also found the tab off the governor arm in the sludge. That may be why it was parked, who knows.

I am not looking to run this engine before putting a piston in it. I wanted to start it to see if I could get away with a standard piston for the time being. Sorry if I made it sound like I wanted to blow up a 16HP Kohler. I'll tear it down and take some bore measurements to determine a path forward. CADPlans, thanks for the explaination, I'll check the bottom of the bore for a step.

I've used Cub Cadets since 1986 and have rebuilt a few over the years. I posted because I've never seen this type of failure before. I'm trying to get this engine going for as little money I can to buy some time. I have another Quietline that developed a smoking habit. It's my main worker and this engine could be used in that frame to get me a few months.

Glad you are investigating the problem properly.
A re ring and new piston in a worn bore but not out of speck, will work.
If you were going to use it as a primary mower/tractor I'd recommend a proper overhaul.
But many enthusiasts put few hours per year on their engines and tire of them/trade, long before they get to a point of a mandatory overhaul.
inspect/mike the crank journal closely,a failure there can destroy an engine.

[Bob95065]

I completely tore the engine down after work this afternoon and I'm glad I did.

The engine was run low on oil and the big end of the rod has transferred aluminum. The piston has damage on the valve side where the hole from the cylinder to the breather is. The skirt is broken on the other side. The rings did not have rust on them which is not what i expected. I think the piston damage on the valve side is what was causing the engine to not turn over.
There were broken thin washers behind the breather. This engine needs a rebuild.

I did measure the bore and it is in spec but im going to have a machist look at it. Thanks for the advice and encouragement to look further.

Where is the best place to get parts for this engine?