1986 Honda HR214 top oil seal leaking oil

I have a 1986 Honda HR 214. I run the mower for 5 minutes and it starts to leak oil from underneath the flywheel. Replaced the top oil seal and have drained and replaced the oil. Still leaks after 5 minutes running. Any ideas what could be causing the leak? Only leak path for oil I can see is the seal. Crankcase casting looks to be completely intact.

Purchase new OEM seal, remove old seal, inspect crankshaft for burrs, clean & inspect aluminum at top of engine where oil seal will be seated, if you do find burrs on crank or aluminum use fine grit 150 paper to repair. When installing new seal put a small amount of automotive clear silicone on outer surface of seal and use a deep well socket and hammer to install seal, make sure socket outside diameter is same as seal outside diameter.