Hi I'm working on a tao tao 125 atv it was brought to me as a basket case it was literally in boxes in pieces because it was taken apart by the owner trying to fix.......I have no idea what. I have replaced every switch, button and wire on this thing and it will not rotate fast enough to start. I've replaced the starter and battery 2 times to be sure it wasn't the issue. I even replaced the engine with a new one but still same problem. I'm at the end of my rope with this and completely at a loss can anyone help? Thank you in advance

 

It can only be the thick wires from battery to solenoid, to starter, or battery to earths on engine and frame. The terminals need to be clean and tight on all of them. Batteries need to be fully charged too. New ones are not always charged up when you get them.

 

Thank you for the help but I know for a fact it's not a low battery I've made sure of that I replaced it and fully charged it. As far as earth grounds and battery cables I've been through them also

 

Remove the spark plug cap and see if the engine spins any faster. This shouldn't make any difference, as you have changed both engine and CDI but worth trying, to eliminate the possibility of the ignition timing being out.