I'm new here but have a question
 

Hello my name is Jim and I bought a Taotao 110 and have done a lot of work to it. My question is, why won't the starter spin when I hit the button? I bought a new battery (it reads 13.12 on the multi), new starter, new handle bar switch, new key switch, new wire harness, but when I put the battery charger on it it starts. Can someone help please?

If you are putting the charger onto the battery, either the battery is flat or a dud, despite the reading, or the battery terminals are not making a good contact.

Thank you merryman, I tried cleaning the posts with sandpaper, hooked it back up and nothing. Another thing, when I turn the key on the tail light comes on, when I hit the start button it goes out, when I release it comes back on.

See what happens to the voltage across the battery when you press the start button, if it drops much below 10v it is either flat or a dud. Other posibilities are bad connections at earth points or on main positive wires, but that shouldn't be affected by whether or not the charger is on.

Solved
 

Thank you marryman,
It was the battery. The place I bought the battery sold me one that wasn't the right size. I also went through all connections and checked my ground. I added some lights. It looks pretty good I think. I'm not sure if we can post pictures but If I get the green light on it I will. Thank you again marryman, you were a big help.