Carburator Overflow

I have recently acquired 1985 VF1000F and while checking the condition of the bike I have found engine oil contaminated with gasoline.
Any suggestions what the culprit may be.

Possibly a stuck float or needle valve in the carburetter allowing fuel to run down the bores

Try to see if the vent pipe that goes into the swingarm is blocked

Thanks for inputs. I will remove carb. bank for complete check.