by pumpguy » Mon Oct 17, 2022 3:59 pm
Please keep in mind I don't have a Hummer anymore, and haven't for many decades. I do have a magneto from a 55-57 B model converted to fit on my 250 Maico to provide magneto ignition and some direct lighting.
That said, and as I understand, the magneto set up you describe is the later style with two (2) primary LT coils and needs one (1) external HT ignition coil. It also has two (2) sets of points. As I understand this set up, one set of points times the ignition while the other set steals current from the ignition LT coil to power the stop light when needed.
The 55 - 57 B model magneto ignition coil is a primary / secondary type coil with the HT spark lead coming directly off, resulting in a completely separate circuit which has no relation to the lighting circuit. This is the same arrangement as an old breaker points ignition engine like a lawn mower or outboard motor. In fact, this same primary / secondary coil is also used in some old Mercury outboards.
Hope this is helpful.