So I'm trying to help my brother in law out with his '05 400EX. It died while riding it and now won't start. I thought a spark plug would be a quick and cheap idea so I changed that and still nothing. The starter is spinning and the starter clutch is catching because I could see the piston moving while I had the spark plug out. I'm thinking it's something in the electrical system but I'm not great with electrical stuff. What should I check next? Any help is greatly appreciated.