I just acquired a 1977 NC50, my first moped experience. Previous owner said it worked when parked several years ago (of course). Got a battery, some gas, a little penetrating oil in the jug. Good news, the horn works. Bad news, I can wind it up but nothing happens when I try and start it. I'm guessing it's locked up. Is there an easy way to see if it will turn over? Where should I start?