Help identify this 2-stroke engine failure (Not from a ski)

[Zero Client]

Engine started life at 170psi, and was torn down 5 years later and still had 150psi and was still running like a raped ape.

No black mark under the crown. No signs of seizure.

Yes, its a dirt machine.

The owner is thinking maybe from coolant ingestion.

I'm thinking; sand ingestion? It doesn't resemble a bottom end failure to me - usually bottom end failure puts pin/rod type of damage. Could be detonation? Squish was at about 48thou. I'm not sure - I'm just trying to help identify the cause for someone.

 

[scotts2t]

does not look like bottom end failure to me, bottom end failure ususally leaves sharp dents of all makes and sizes from crank bearing races. does not look like detonation or water ingestion either. to be honest it looks like a small round ball shape of metal got sucked up or possibly a reed screw?

 

[MTRHEAD]

Looks like a miniature version of when the screws blew out of my VForce 2 reeds. It is a mechanical event. Looks like something of constant consistency caused the dimples versus detonation.

 

[Zero Client]

K. Having him check his reeds. He actually had not yet removed the reeds from the cylinder.

 

[pepper22]

what does the cage & needles look like for the piston pin?
I think the cage cracked & the end of a needle bearing broke loose.

 

[DAG]

Photo of the dome with the black dot circled in red. Is that a hole or something embedded in the alluminum? Looks like whatever that is was making all the marks...

 

[Whakanui]

How about spark plug electrode