Motorcycle Repair: FatBoy Engine Noise, crankcase ventilation, crankcase pressure

Question
My 97 Fatboy has developed a problem. On start up, if it backfires it will blow the oil cap off the tank and spew oil all over the place. When running it has suction and will actually hold pressure on the cap. After a few minutes of running, the engine will "squeek" upon shut down...sounds like the beginnings of siezing. It has great compression and power (9000) miles. The oil light goes out but I am not willing to run it too long as I'm afraid to do any long term damage.
What do you suspect?Could the oil pump be malfunctioning, is there some kind off crankcase ventilation sysystem that would prevent normal oiling? It has never been modified or run hard.
I was told you were the man...I'll await your reply.

Answer
YOU HAVE CRANKCASE PRESSURE YOU SHOULD NOT HAVE, YOU HAVE MAYBE A BENT OIL LINE OR A BAD OIL FILTER, IF IT BACKFIRES THROUGHT THE CARB IT IS TOO LEAN. GO UP 2 LOW SPEED JET SIZES, WHEN THE ENGINE IS RUNNING AND BIKE STRIGHT UP. REMOVE DIP STICK AND LOOK INSIDE OF OIL TANK WITH A FLASH LITE. IF YOU SEE OIL MOVING THE PUMP IS PUMPING AND THE OIL IS RETURNING TO THE TANK. I WOULD HAVE TO LISSON TO THE SQUEEK TO HELP YOU IN THIS PROBLEM.    JOHNNY