Sounds like the charging system is not working or the battery has a draw on it or the battery is weak. You will need a voltmeter to test the battery and charging system. Make sure the battery is fully charged and the post are tight
check the battery voltage with the
motor running then raise the rpms up to 2000
let me know the results
it is the stator #9 under the left side case cover
I have seen brand new batteries that were bad
you also have a regulator/rectifier and flywheels that were bad cause the unit to charge
the stator is a $400 part.
with a volt/ohm meter test can be done to confirm a failed part instead of just replacing parts.