My cousin bought a 2001 Blast with 3,000 miles on it. The bike had been sitting for a couple of months and the battery was dead. He had battery checked and it was shoted out. He put a new battery in the bike and it cranked fine for a couple of days, then wouldn´t crank the bike. Checking the battery at full charge, it´s reading a little over 12 volts with the switch turned off. When the bike is cranked, voltage drops slightly, indicating that the alternator is not charging. Has anyone else had this problem? Where do I start with diagnosing the problem?