TOPIC: Excessive crankcase pressure-Cause? Fix?

I'm hoping some of you can help. It runs great but seems to be building crankcase pressure and finally kills. When I raise the oil fill cap on top I can hear it spew air.
Any ideas? Thanks in advance. Tony 256-504-7898

Check your crankcase vent tube that comes up from the oil sump, brass tube, then hose that loops up to top of crankcase cover (oil pan looking thing on back), then loops down and exits through back side of motor pan. Bees and caterpillars get in there and plug it all the time, I see this frequently.
Check it and report back. $5 says if you blow into the vent hose it's plugged. Also check your telltale at same time, bees get in there too if there the restrictor is not installed like it should be. I see that on 50% of motors up here.

Thanks Bill, your hint made me realize we must have forgotten to punch hole for crankcase vent in the homade powerhead base gasket. Easy fix, done.