According to the specs in the little booklet that came with my kit, the white wire from my magneto is supposed to be able to supply half an amp at 7.5 V. (The booklet says it's for the "A80" motor. My engine has the slant head, and supposedly 47mmx40mm B&S. I haven't verified the stroke, nor do I know yet which style rod and piston pin location it uses. I'm just including this info for you or anyone else trying to surmise the provenance of my engine.)
When I get the lighting that I'm planning for my bike, I was planning to rectify, filter, and boost this to a low power 12V system.
I have not yet taken any measurements or connected any loads to the white wire side of my system, but I'm a little puzzled at all the advice I've seen on the forums about not using the white wire, especially if it's just to drive a small resistive load that can use AC and won't try to draw too much current.
I'll be doing some experiments later, and I'll let other know what I find out and what successes or failures I have. I imagine people often ignore these specs and connect loads that draw too much current and cause magneto trouble.
In your experience is there really any problem with using the secondary magneto coil for small loads within the specs?
I made a mistake. I rechecked and like Crassius said, the white and blue wires are just soldered together to the same tab at the magneto coil. So my booklet is wrong, (and probably means this is not an A80), and I have no built in auxiliary coil to run my planned electrics.
I'll still be looking into my options. From the outside, it looks like there may be a second coil, and they just didn't bring it out separately.
And off-topic, I still need to look into some of the designations people use for some of the engines and figure out just how to refer to mine. Maybe it's a PK80? I think I'll probably have to pull the jug to determine the rod and piston setup in it.
On mine, and I should've photographed it, the blue and white wire come off one tab, and the black wire is connected to frame ground with a soldered jumper, and also to the other tab. So they have grounded out the lighting coil.
I think I will try undoing the manufacturer's mod, and restoring it to the above configuration to see if I get my power option back.
After all, I bought this kit to tinker with.
I'm also going to be learning more about how the CDI is triggered and possibly playing with adjusting the ignition timing electronically.
I know this is not new information to the experienced guys here, but I'll share what I did and found today anyway.
Though my magneto came with three wires, it is really only a two-wire magneto. I unsoldered the black, blue and white wires from it today and checked the resistance. The two tabs are isolated from ground, and show a resistance of about 550 ohms through a single fine winding each end of which is terminated at the two tabs. There is no winding on this magneto for lights. I think I'll order one from eBay that seems to have a functional white-wire coil and after testing it, take it apart to see what the winding looks like. (I hope it consists of larger enameled wire wrapped around the first winding so it's easy to get to.) I think it should be easy to add the 6V or maybe even fit a 12V winding on these.
If anyone already knows all the construction details of these and wants to share, please do. I bet it's already in the forum posts if I do some searching, huh? LOL. I'm such a newbie here. I already found a post by Crassius where he discovered the same thing about the blue and white wires being common. In my case today, when I reassembled everything, I decided to removed the white wire entirely. While it might one day serve as an emergency replacement for the blue, it probably won't, and I'd rather remove stuff that isn't functional or being used.