Hi King.P. it will run with knackered crankseals, you say ran for 5 mins , was this with choke on? did it run with choke off ,?
you"l not find fuel behind flywheel ,as it will be sucking air in,,
Dry plug - defo pllot or choke jet clogged,,, how is the spark,,, oh change the plug , as they can fail when warm,,,if old,
And its a Liquid cooled,,,is there a knackered head gasket,,, all these thing need illiminated,
U tube will show you a leak down test for crankseals,,