Hook up a voltmeter to your new battery while it's off, and while the bike is running (rpms should be maybe 3k rpm? higher than your 1k rpm idle, anyway). The voltage should be much higher (14v) when the bike is running because the stator and rectifier/regulator are generating the power to run the bike as well as recharge the battery for the next start. If your voltage is tapering off slowly while the bike is running, then your charging system is messed up. The stator is a common failure point on this bike, and is the reason a lot of them sit for a long time and are then sold off.