1980 Honda cm400. Gasoline in oil?

I'm looking into this 1980 honda 400 as my first bike. I'm well versed mechanically, on similar bikes and cars as well. The only real issue is that I can clearly smell gasoline on the oil dipstick. The owner stated it will most likely need new piston rings but I saw no blue smoke and minimal white smoke as the bike warmed and idled.
I'm curious as to what could cause this… The carb must be flooding over, through the cylinder etc. There's a small leak in the fuel line from the petcock. Maybe this is causing the fuel to constantly be drawn into the carb?
Any input is appreciated!

That would be my guess. Maybe rebuild the carb and make sure the petcock positively shuts off fuel, be sure to change the oil.

Yes, carbs overflowing into the cylinder and leaking past the rings.
The fuel line will have nothing to do with the carbs over flowing.
The problem is probably a leaking float "needle & seat."

Previous owner has NOT turned off fuel petcock when parking cycle, float needle and seat 'weeping' gas while setting and the resultant overflow has been dripping into cylinder and washing past rings into crankcase. I have a 1981 CM400 used as a trainer- getting carbs off and cleaning/rebuilding with new seals, needle and seat ethanol proven is relatively straight forward but sort of time comsumeing- read the manual twice, set aside a whole afternoon, get some towels and rags for cleanup. Little putt has a new student to teach- so far it has taught student to wear long pants when moving it around after riding- don't lean its pipes against bare legs. I have caught student not turning off fuel petcock often, have told him couple times and have threatened to pull battery cable on him like I did with previous student. Minor problem with earlier vintage cycles- many later models had the vacuum activated fuel tank shutoffs or occasional electric shutoffs and that is what the MSF trainers mostly have on them so students don't get into habit of turning fuel valve off and on.