Motorcycle Repair: Battery keeps dying, yamaha xtz 750, yamaha xtz 750 super tenere

Question
Hi
I just put my 1990 Yamaha XTZ 750 Super Tenere on the road after 2 years of dry storage. I bought a new battery, started it, rode it for a day and all fine. 2 days later: battery totally dead-not even enough power to light the neutral light. Jump started it via car battery and rode it for a few hours and battery charged up again so the alternator must be fine. Again, it was OK for 2 days, then totally dead battery again. I am not leaving any lights on and there is no alarm or other equipment fitted. I jumped it again and now it struggles to keep running. When I put a load on the system like the brake lights, the revs drop. I checked the rectifier and it was hot as hell. Also the plastic connector with the 4 wires to the rectifier is melted and the connectors junked up with molten plastic. Checked all other connectors and cleaned them up.
After trickle charging the battery for 24 hours, I am only getting a 7.5 V reading from the multimeter so I think the new battery has been damaged.
Question: Could there be a short somewhere that is causing the battery to go dead or could there be an electrical problem somewhere causing the rectifier to fail or is the rectifier what may be draining the battery while bike not running? Could this be causing the battery to die so quickly (sometime overnight?) I don't want to put in a new rectifer only to have it fail again...and likewise, I don't want to put a new battery in and trash that as well. Before I put the bike in dry storage, I killed a couple of batteries and always thought it was because I was not using bike enough, but it seems there was another problem all along that was draining them (and killing them.)
Any help would be appreciated.
Thanks
Peter.  

Answer
Hi Peter,

The charging system components need to be tested. I can send you general test info files, but you didn't include an email address as requested. I recommed the service manual for detailed tesing. The factory manual is best and most accurate.

There's definitely a problem with the Regulator/Rectifier getting too hot. RR's are designed to shunt excess charging current in the form of heat (hence the heat sink fins on RR).

A series of tests with your VOM will determine the cause.

Respectfully,
Mark Shively