1992 225 piston ring failure

[chickencake]

My 1992 225 2 stroke recently died!
the piston ring has been imbeded into the crown and also damaged the head.
the engine wasnt pinging or runing lean nor was it over loaded
it was running at 5000rpm with yamalube and high octane fuel.

the engine was sold to me on my current boat having done 44hrs, its now done around 55hrs.

upon removing the cylinder head of the starboard side there is a .25mm oversize piston installed and simular damage left on the respective head from the last rebuild.

what would be causing this! bits of bearing???


current damage.

possible causes? where can i get parts? whats the go with installing a sleeve as the bore is very damaged.
any help would be great thanks tom

[rodbolt17]

judging by the piston crown erosion on the ex side, it was running lean.
overproping can leave similar erosion marks.

[robert graham]

Maybe ring got hung in a port?

[chickencake]

well i removed some of the material thats stuck in the piston crown its too thin to be a piston ring and the rings are still in the pistons? back to the drawing board?

[Sequoiha]

is the ring locating pin still in the piston, if this comes out it will bounce around and cause this damage,

[robert graham]

Maybe a piece of a reed or reed cage?...

[chickencake]

piston ring locators are cast into the piston?

the reed cages/reed assembly is complete nothing missing

just a thin ring of metal from somewhere appears to have gone threw it...
thinner then a piston ring

[robert graham]

Maybe the ground electrode broke off the spark plug and was rattling around in there?...just a thought...