Motor Stuck

[Eugene]

So, can I just replace the piston?

You could and everything would probably be fine. But if this were my engine I would freshen it up. Depending on measurements, minimum would be rering, lap valves, new rod and main bearings.

[lazyuniondriver]

Just out of curiosity, were you able to determine what the debris was composed of?

[Yogie]

Just out of curiosity, were you able to determine what the debris was composed of?

Wondering that myself, why would a new built engine have debris like this ?

[Eugene]

Check the head for damage. What ever knocked a hole in the piston probably did just as much damage to the head.

What is the history on this engine?

[mrdibs]

I didn't find any damage to the head. Debris seemed to be just part of the piston. I did not replaced the pistons and one of them was seized when I started. Could be I damaged it while freeing and it just now caught up with me. I guess the debris was what got it stuck, because once the head was off, I was able to turn the motor by hand. I guess the good news is that this all happened on a cold engine at idle. Otherwise I'd certainly have cracked the head or worse. I'm too poor this winter for 4 new pistons, so I'm going to replace the one for now and do the rest in the Spring I guess.

[Matt Kirsch]

There was probably enough debris piled up to stop the piston just shy of TDC. That's why you couldn't budge it until the head was off.

[mrdibs]

Well I found a used piston and installed it during Sandy. Engine running again, but it does puff a bit of smoke when I goose it. Probably more than usual, but I need to work the tractor before the snow flies so it is what it is. Visual inspection of cylinders revealed no damage. Head is ok and I used a new gasket. To the horror of some, I'm sure, I transplanted the rings which were only one season old and seemed fine. But I did use a new rod bearing. I'm probably due for a bore and new valves, but I'm tempted just to run it till it won't, then worry about it. Thanks for the help everyone. How I ended up with a hole in my piston remains an unsolved mystery. Tonight I plan to pull the plugs before starting again, just to make sure I'm not getting water in the cylinders.

[skylor60]

What did the spark plug look like in that cylinder?

[mrdibs]

What did the spark plug look like in that cylinder?

Same as the others. A little black - gap was fine. Carbon buildup was minimal. The engine was seized when I originally started working on it many years ago. Very possible I damaged the piston while freeing it up, but got away with it for almost an entire season. Really it should have been #4 because that's the one I had to smack the hardest, but I probably hit #3 too. Years of mistreatement and overheating may have contributed to weakness in the metal. If I find a new set of pistons I can afford, I'll replace them all - maybe bore it too.