I could not get the low cost lighting coil to fit under my flywheel, so just built my own lighting coil using the center from an old stator adn 20 guage magnet wire. Works OK, but nothing as bright as the high dollar units. Essentially, I have enough light to make it back to the van in the dark (which is exactly what I wanted), but would never consider using it at any serious speed. Also, when I built my lighting coil, I did not use a case ground as I plan to add a rectifier and battery at some point in the future. I will then have light even when the engine is off.
Good luck
Rick