Old wing question

[Cruzin]

Last fall as I was trying to get my Gold Wing into the trailer for the winter. It refused to start I heard a loud bang which I didn't like, it spun over so many times it actually melted the lead post on the battery and finally sized up.

A month ago I pulled it out of the trailer and after some investigation found out that the gas that was in the tank all transferred into the crankcase So I change the oil and filter and try again. It started and moved a few blocks but it had no power. Like a dead cylinder. I decided to look at it again yesterday and all of the fuel is in the crankcase again

I have blown up a lot of motorcycles in the last 43 years of riding but have never seen this happen

Any ideas