With the bike having sat for 5 years and now behaving as described, I would have your battery professionally load tested at shop that specializes in motorcycle batteries. You can have a meter show plenty of voltage with no load, only for it to tank when the starter button is pressed and a load created. It sounds like you are on the right track, but it never hurts to make sure your foundation(battery) is sound before chasing symptoms.
I would go deeper into detail, but the forum members seem to get upset when I help out. God forbid I correct or ask for clarification of someone's misuse of terminology.