Magneto for a 12V Chang? - by Ross Kowalski
Really, all a motorcycle needs is a magneto and a lighting coil. They are reliable, so reliable that most piston driven aircraft use them. (Of course they have a backup as well.) They are also simple and clean, no wiring, just bolt them on and time them. I chose a Wico X because it is one of the most common and by extension, inexpensive magnetos available as well as having lots of replacement parts and service info. When I started looking for a magneto, I found a guy selling them as part of an estate. The magnetos were freshly and professionally rebuilt. I got a very very good deal on that magneto.
A little about magnetos. The X does not have a spark advance, manual or automatic. It has an impulse. Impulses are a mechanical sort of spring assembly that retard the first few sparks as well as giving a slightly stronger first spark. The retard is adjustable. There are old tractor resources on the Internet with all kinds of info on magnetos if you are interested.
So where am I on the magneto project? Some recent talk on the Chang Jiang Experience forum about ignitions got the magneto out of retirement and even photographed.
A good choice for a magneto would be a Fairbanks Morse unit from a little industrial twin. (The FM is used on HD sportsters.) Of course they cannot simply bolt one on as we can because of weird V-twin timing cam.
I tested the first version
which worked fine, but without the impulse, I had to
manually retard and advance the timing. It ran fine
though the timing adjustment will need to be made better.
I have a couple of systems in mind, but haven't put
anything to metal yet.
|A Wico X magneto grafted on to a CJ M1M/M1S point housing.|
|This is a closeup of the nameplate on the magneto, though almost any magneto would work.|
|I removed the impulse and drive gear from the mag. I don't even know what engine it was for but it was gear driven.|
|The is the modified timer shaft. I ground out the center tower for clearance.|
|The first system I tried had a rubber coupler disk that fit over the two pegs visible on the original unmodified Wico impulse plate.|
|Here is that system. Notice how far the CJ timer plate sticks out of the bottom of the magneto.|
|I turned down the point housing at a freind's shop.|
|I then cut slots in the hardened impulse plate with a angle grinder, took off the little pegs, and shortened the Wico input shaft a centimeter or so.|
|The result is much shorter.|