That bike should have a hook up for a volt meter already in the wiring harness. My g/s did. Look at a wiring diagram and you should be able to find it.
"Between two explanations, choose the clearest; between two forms,
the most elementary; between two expressions, the shortest."
Between two motorcycles the simplest (DW)
Eugeni d' Ors (1881-1954); Spanish writer.