My son's 110 BMX atv with a loncin engine has no electrical power even with new battery. I am an electrician, but i need help in troubleshooting the various parts that would interrupt power to the starter, etc.

 

What do you mean by no elecrical power? Do the headlights work? Brake lights? (Ignition switch must be on of course).

Have you checked the main fuse? Get a voltmeter and measure the voltage on the battery terminals. What do you measure? Turn on the headlights. What do you measure then? Short across the starter solenoid terminals with a screwdriver. Does the starter turn? Do this with the headlights on (assuming they will turn on). Do the headlights go out when shorting the solenoid?

 

Lynn, thank you very much. Through this site i was able to obtain a basic schematic for the electric's in these small motors. i found the problem being that i had power from the battery, through the voltage regulator, and then to the plug connector that eventually feeds the ignition switch. Took the body off the atv, removed the ignition switch and found that the solder connection for the "hot leg" from the voltage regulator had broken off. Too small an area to solder, so i bought an $8.99 ignition switch from "Auto Zone", installed it and fired it up. Still have a short some where in the lighting, and or the kill switch circuits, but the thing runs fine now. I am going to by pass the original kill switch and just wire in a good kill switch to protect the rider. These "cheap" atv's are a good deal, but you have to put up with the small problems associated with a lack of quality control.
Thanks for your input.