I. Just read your whole post, welcome to the fun. I have a few comments and maybe some help.
1. The starter gets it's ground where it touches the engine case, so clean those contact points!
2. The bolt on the side of the starter has a wire attached on the inside, DON'T turn the bolt, only the nuts, or you will break the starter.
3. Starters can take quite a few amps to turn, make sure the battery is fully charged, & you use a big enough wire to test it. Auto jumper cables are big enough, but their long length can be a problem for a marginal battery.
4. If you bought a chinese starter then it might be defective, but taking it to an auto repair shop to be sure, is a good step too.
5. Hondachoppers.com has a simple wire diagram for a bobber, but learning to read the schematic in the manual is priceless.