03 xlt 1200 blown cylinder help

[bill34]

First time posting...
Looking for some help/advice on what to do. I bought an 03 xlt 1200 with 56hrs on the clock. Took it out for an hour and it ran great. The next week I took it out and it blew the PTO cylinder after about 2 hours of riding. Ski shut off and then would not turn over like the battery was dead. While trying to re start it i got a water temp alarm.

Checked compression and got 120,120, and 30.
I tore the engine down and found the PTO cylinder and piston are toast. So the apart i need help with is figuring out what caused it. Ski has 1/4 tank of treated fuel and the oil tank is half full. Oil line did not pop off and is not leaking. PTO cylinder was dry when I took the head off. The other 2 cylinders look perfect. powervalve did not drop in. Ski does have cat con but is in excellent condition not broken or clogged.

Any ideas or things to look for?

[800AMSOIL4U]

Rear seal went out or crap in the carbs. The head gasket is good? Post up some pics for us to help you figure it out.

[bill34]

Here are some pics

[bill34]

here are some more

[bill34]

Ok I finally got around to pulling the carbs. I opened them up and they look pretty good filters were not clogged and returns were not clogged. I believe the head gasket is ok since there wasnt any water in the engine or signs of it leaking. How can I tell if it is good? I had already pulled the cylinder so I wont be able to perform a leakdown test until I put it back together. I have a good used oem cylinder and piston to replace the bad one. Any tips or tricks for install? Once I get the head back on I will pressure test and post the results. I will try to make some time this weekend to get it back together.

Any advice or comments would be appreciated

[Helsinky Smashrod]

Is that an indent in the top of the piston? Pretty sure I don't have that same indention on my pistons. Did the piston impact the spark plug? If that's the case then you could have had a bad wrist pin bearing.

[bill34]

Yes there is a chunk of the piston missing. Spark plug doesn't look damaged so I don't think it hit. Either way I am going to replace the wrist pin bearing.

[TX21]

Those ware marks on 4 corners like that mean (I think) the piston is too big.

[bill34]

The marks on the piston are deep scratches and gouges. The engine is all original so I don't know why it would be too big.

[bill34]

I got the engine back together and did a leakdown test. It was able to hold 6lbs for more than 6min. I sprayed down all the gasket areas with soapy water and didn't see any leaks. I will move on to the carbs next.

Is there a way to test the oil injection pump?

Is it a good idea to put an inline fuel filter after the water separator to keep the filters in the carbs from clogging up?