Coolant exiting from spark plug hole and between cylinder and engine block

[Mikeyx]

You are not gonna believe this... but I'm not making this up.

On her maiden voyage with the new piston & cylinder, I got again a piston failure!

Now riding with a 180 main jet instead of 175; recommended W24 plug instead of W22. Riding at 95 km/h and revving the engine in 2 s intervals instead of a steady throttle. Some 1 km on a highway the engine stalled, the rear wheel locked and gave a good rear slide and almost got rear-ended by a street bike before I found the clutch lever. Scary shit! Engine again with no compression.

Findings:

- spark plug intact and having a healthy dark brown colour (as if mixture was ok)
- top of the piston intact w/o any damage whatsoever (timing is correct?)
- sides of the piston having identical damage as in the pic I posted above

- the oval timing thingy in place in the stator backing plate (timing correct)
- crank shaft can be rotated by the coolant pump impeller (cooling ok)

I mean, does it leave any other option apart from an incorrect oil/gas mixture?