@Everythingispenguins@lemmy.world I have a 2007 Rocket 3 and a Riva 125 scooter. They both run, I'm just too lazy to pull them out of the garage and do the actual work of putting a jumpstarter to them and air in the tires.
Get a desulfator. They're cheap now online; you don't even have to build your own anymore. I've successfully rescued several knackered batteries with mine. I'll warn you it does take several days of doing its thing to restore the cranking amps on a battery but if it's dead just due to neglect and sitting there discharged it usually works.