t-rav.15

I was looking to buy a new bike and I've found a 1978 Yamaha 650 Special but the bike has some problems... "THE PROBLEM IS I STARTED IT LAST SUMMER WITH THE BATTERY CHARGER AND FORGOT TO TAKE THE CHARGER OFF AFTER I GOT IT STARTED. THE BIKE DIED AND SMOKE CAME UP FROM SOME WHERE. AFTER THAT COULD NOT GET POWER ANYWHERE." I was wondering if there was any common problems from leaving a charger on or if it would be fairly easy to fix. Thanks.