My son has an ata110-b that every time you hit the start button on the handle bar the main fuse blows. Plus when you step down on the break to start the break light will not come on. Anyone have any idea.

 

you probably have a dead short in the wire harness some ware.. I would start by finding the light connections in the harness and unplugging them. On mine if the tail lights are plugged in it will not start. Just have not had time to fix

 

Yup, for sure a short. Inspect your harness for any kinks or maybe something clamping on the harness causing it to ground out. These are hard to find as the harness is wrapped, but you have no choice but to find it.