Old gas…

Hello! I bought a Hyosung Cruise (for the city) cheaply a month ago and, after it was shut down five years ago, brought it to work (everything that is changed). Only the old petrol is still in the tank (was full, and with the petrol prices the workshop meant, I can still drive with it). It also runs quite good – when it is running. Can starting difficulties lie on the old petrol?? Or is the carburettor poorly tuned (it runs rather lean). Batt erie is new and full…