I agree with LeDude. Charge the battery up then have the battery load tested and if bad replace it.
If the battery test good then I would suspect you have a problem with the charging system. A quick test is to crank the bike then check the DV voltage at the battery with the engine running. You should be getting between 14 and 15.5 VDC with the engine running at 5,000 rpm. If not then you likely have a problem with either the stator or the regulator/rectifier or both. There are test you can run to find out which. To do them you will need a multimeter and you will need to remove the left rear frame cover to gain access to the plugs. The left rear frame cover is the one the fuel door is mounted in.
If the battery test good then I would suspect you have a problem with the charging system. A quick test is to crank the bike then check the DV voltage at the battery with the engine running. You should be getting between 14 and 15.5 VDC with the engine running at 5,000 rpm. If not then you likely have a problem with either the stator or the regulator/rectifier or both. There are test you can run to find out which. To do them you will need a multimeter and you will need to remove the left rear frame cover to gain access to the plugs. The left rear frame cover is the one the fuel door is mounted in.
