Small update:
Fuel system cleaned & checked - filter ok, bowl cleaned (no sign's of buildup) and tanked checked
Intake removed and can see 1 valve working as it should (cranking by hand slowly)
Engine oil drained & checked - oil in ok condition and no visible metal filings or fragments from mechanical failure
Replaced spark plug - still just fires once and then just keeps turning over
No obvious signs of a head gasket failure - no oil or carbon build up around the gaskets
Next:
Reassemble and see if it starts
Then continue with fault finding
Is it safe to run these engines for sort periods idling without the cowling to duct the air cooling system?
