2017 tao tao girls atv. Bought it for my 8 year old daughter. Cleaned the carb,changed spark plug and coil wire. Changed selonoid. Changed key switch. Hers the problem. Bike will start and run. Will just shut off by itself and with the key on it wont start right back up. But if i turn the key off and back on it starts right up. Did the same with the old key switch. Also when running the starter will just engage by itself. Have turn turn the key off to get it to stop. Please help

 

The starter engaging by itself is caused by the start button or the wire from it to solenoid, shorting out. The engine stalling could be a sign of a faulty CDI, but there are lots of other things it could be. Check if you are getting a spark while the fault is on, this narrows it down to being an ignition fault if you don't get a spark.