KX450 no start

2019 kx450 had the bike torn apart, after reassembly press start button and got a clicking whirring noise similar to a when you have a dead car battery. Did that once and now won’t do anything. Battery voltage checks out, but I charged it overnight to be sure. I’ve checked all possible connections everythings where it should be. Not even sure where to start. Can I hook up a lead-acid battery to see if it starts just for testing purposes?