I have a pitbike that is in poor shape but has an engine that shows good potential. I intend to use the engine in an atc70 frame. From what I have found it is 70cc. Anyways, I am fighting a intermittent spark. It will spark for a few seconds and then not spark again until I let it sit for a minute or so. I have the kill switch remove from the circuit, tried a different plug, cleaned all electrical connections, and replaced the ignition coil with a known good one. I did not change the spark plug boot, or cdi box. Any input on what would cause this type of problem?