Re: fuel in air box, and drain tube
Have a look on your spark plugs, I guess one or two of them look really black and wet. Could be a carb or ignition problem, maybe just spark plugs. However plugs often die soon when operated in excess fuel so it might not be the true origin of your problem. Feeling on the exhaust will show you which cylinders do not work at low revs. If 1+4 and 2+3 behave simultaneous, it is probably an ignition problem.
It is quite bad to have not ignited fuel in the cylinder because it washes down the oil from the walls.
So first fix your problem before you continue riding like that.