Main fuse blows.

I put the maxim into dry storage 11 months ago and it was running fine, I removed the battery and wrapped her up all snug. last week I dug her out and fitted a new battery (correctly) fresh fuel, hit the button and nothing! no ignition or neutral lights either. The main fuse had blown, a new one blew also, (without turning the ign on) a quick check showed the battery live going to the reg/rec (which was replaced with an XJ900 one 18 months ago as the battery was cooking) was loose and corroded where it enters the connector block - I cleaned and reconnected this but the fuse still blew, I've tried disconnecting various wires so as to isolate the short circuit but can't pinpoint the problem...
Has anyone else had this problem?
can anyone give me a good testing procedure as I don't have a lot of time to give this.
The bike is far from standard, the main things being the Atari was removed and custom
twin headlights, speedo and warning lamps fitted by the PO, as well as the side stand, and clutch switches.
Any suggestions greatly welcomed! - Thanks.

 

get a 12V bulb and socket, put something on the ends of the wires to the socket that will go into the fuse holder (put a few strands of wire in and jam the blown fuse to hold them) the bulb should light up, it's acting as a fuse but lighting up not blowing out. now as you go through the plugs and connections if the light goes out you found the short.

 

Maybe you put the battery in the wrong way round.

 

"fitted a new battery (correctly)" - Thanks

 

It might sound stupid but some batteries have the terminals reversed.

 

Yep! - Good one polock. thanks... when this storm has passed!

 

FEKKIN MICE!!! chewed up the wiring loom going to the ignition switch, and in two other places! - I hope it wasn't the same mouse I was feeding cheese on toast to on the back wall a few months ago - that would be gratitude! Thanks for the advice.