Motorcycle Repair: Crankcase blow-by, yamaha radian, vent tube

Question
I just acquired a 1986 Yamaha Radian that had been garaged for a couple of years. The gas tank was bone dry so there was no old gas to get rid of. I replaced the battery, added gas and it cranked. As it was running, I suddenly noticed that oil was flowing heavily from the breather box via a drain tube onto the ground. Also, there was not an air filter in the breather box. About a quart of oil drained before I gave up that it was going to stop on its own. The oil also seemed to smell a bit like old gas. The crankcase vent tube must be how it is getting to the breather box but I have no idea why. The engine seems to run good. What should I look for?

Answer
First off: DO NOT RUN THE BIKE LIKE THIS

You have gas leaking through the carbs and into the crankcase. The likely cause is leaking float valves which are either dirty or need new o-rings. You may also have a stuck float valve. You need to open up the carbs and fix this problem.

Once this is repaired you need to drain the oil/gas mixture and put in new oil. Also put in an air filter as it will run poorly without one.