checking battery and charging circuit on a motorbike is easy .
first remove side access panel .
test battery at 12v , then start engine and voltage at the battery terminal should rises to around 14v no more than 15v .
Rev engine to 3000 rpm
Battery charge results
If you have a voltage meter you can do some basic tests.
When the engine has been off for at least 1-2 hours with ignition key turned off,
100% Charged 12.60 to 12.8v
75% Charged 12.4v
50% Charged 12.1v
25% Charged 11.9v
0% Charged less than 11.8v