Re: Electrical System Questions!
My first question would be why do you need to know the direction of current flow? The point is moot however in terms of the ignition system of a Chinese 2 stroke engine because we're dealing primarily with A/C, alternating current, which flows both ways. Hence the name, 'alternating' current. Forget the bicycle frame. It has nothing to do with the circuit that fires the spark plug. The ignition system of your engine would function even if your frame were made of wood, as long as it is wired correctly. The only time the bike frame would come into play would be if you were using it as a ground to kill the engine through the kill switch; and then you'd need a good connection, no paint or rubber between the engine case and the frame's metal or a ground wire from the switch to the engine. There is another misconception that you might need to know about. The kill switch does not open the ignition primary circuit when depressed. It in fact closes a circuit between the black wire, (the engine ground wire) and the blue. Or if you prefer the white and black wire of the engine case (or bike frame if there is a good electrical connection between it and the engine). Forget about what you've been taught about electron flow. It has no bearing on your ignition system. Now let me confuse things. I use a battery (D/C power source) to power my lights. I run a wire from the battery negative terminal to a place on the bike frame, then run a wire from the positive terminal to a switch then out to the head/tail lights. I either ground the lamps/socket to the light case which is attached to the frame or a seperate wire from the lamp socket to the frame. The frame then becomes the conductor. This allows me to run a single wire to my lights instead of two wires; saves wire and looks cleaner. Hope these replies helped you and answered some of your questions.
Age and Treachery Will Always Triumph
Over Youth and Skill & "Charlie Don't Ride"