Weird!! blowing 40 amp fuse on 955 with ignition off

Hi guys....I'm new so be gentle!! I've got a 955i street fighter er which has sat for a few months in the weather. I decided to attacknit today and found this problem which it didn't have before!

Battery charged up, but when reconnecting it kept sparking. I had positive on and was connecting negative but it kept sparking anyhow! Then it blew the main 40 amp fuse. The ignition was off with key removed so why is it happening? I've since removed the main power lead going to the alternator and tried a new fuse which didn't blow, but I have absolutely no sign of life on the clocks or horn or anything. As if no battery connected?? So in my infinite wisdom or STUPIDITY I connected jump leads to my car thinking maybe battery was goosed. Alternator still disconnected, It tried to weld to jump leads to the battery!! I managed to pull them off, but it literally has melted part of the negative terminal. I'm at a loss!! Please help me for my next move!!!!

 

Thanks for the response......sorry to sound stupid, but positive terminal from the alternator to ground? believe it or not I'm spanner handy but I think I missed the electrics section of bike brains!!! Battery is already out lol......new one on order!