1/. its running on 2 stroke mix
I've flushed the tank with fresh fuel, so no to this one.

2/. It needs new valve guides and valves.
This sounds likely. Not yet sure if the guides are removeable - B&S
"classic" sidevalve engine.

3/.Unlikely, it needs a new piston and cylinder as some asshole has let it
run out of oil and its siezed and damaged the bore/piston.
Agree.

I'll pull it apart over the weekend and investigate.

Alan.