Board index Flathead Power-Technical Questions, Answers, and Suggestions Knuckles Wico horiz. magneto

Wico horiz. magneto

Post Mon May 05, 2008 10:00 pm

Posts: 16
Location: LA
Seems like it's been dead around here lately.... maybe I can get someone's attention. I have the mag and the drawing, and from what I can tell the timing becomes fixed, that tells me the layout of the bolt circles becomes critical... the layout seems to based on the gen screw holes so... does a set of dowel pins with centers machined in sound like the right approach to get everything squared away? Does anyone have any experience with these mags, good or bad?
Thanks, Brad

Post Tue May 06, 2008 11:50 am

Not sure what you're asking.
The mag chain tension is adjusted with shims - this means that the bolt holes only need to be close enough to assemble. There's no point in trying to get the exact pitch centers, since after the 1st use you'll have to shim the mag anyway for chain stretch.
I have a feeling that some hole elongation to permit rotation around one bolt, or movement through more than 1 plane will help.
If it's too far away, you'll know it because you won't be able to get the chain on. If it's too close the chain will be slack with any shim that fits.
The original timing is done by selecting the 42 gear tooth position (17.14° each) vs. 36 tooth chain tooth position (20° each); 1 ahead + 1 behind = 2.9°, 2 = 5.7°, etc.
If you make an offset key for the mag sprocket, you can use:
1. offset key, CW
2. neutral key
3. offset key, CCW
I suspect that a tensioner could be added to the "hot" (loaded) side to permit minor spark adjustment, but I've never seen one. It could be made externally adjustable (like a primary chain) using the ignition hole for access, and an Allen key on a universal to rotate the tensioner screw on a Teflon "shoe".
Another alternative is to add 1 link to the chain, move the mag farther away, and leave room under the mag to rotate it considerably, using a jacking screw from below with a wedge-shaped block to support the bottom.
With some surgery, a better adjuster could be added from below. Another sprocket is placed in between the chain rows, and is jacked up or down by a screw from the bottom of the case. Jacking it down just removes tension on the chain, but jacking it up rotates the mag sprocket CCW, advancing it. This is an engineering nightmare though, since the extra sprocket must be held in alignment but be free to move on a restricted path with the screw.

Post Tue May 06, 2008 6:02 pm

Posts: 16
Location: LA
Thanks Panic, I realize that the initial timing would be set by, timing the gear and sprocket together in relation to the crank, and I also understand that shims under the mag will adjust the chain tension, wouldn't clearance in the mounting holes allow the shim that sits in the gen. stand to rotate, along with the mag changing the timing? Giving the effect of the jackbolt idea? That is where I feel like the layout becomes critical. It seems to me if you miss there, you will continue to miss all along. Typically in my trade dimensions givin in fractional form have looser tolerances than those givin in .00 or .000. So with that being said you are probably right. I guess there is one way to know for sure... do it. Thanks again, if anything else comes to mind I'd love hear it.

Post Wed May 07, 2008 9:19 am

I would prefer jacking it because after a bit of math the screw pitch makes 1 turn = X° of advance, so it's linear and doesn't require much un-bolting. A 1/4-28 NF screw operating at 90° to the rotation moves the mag .0357" per turn, .006" per hex flat, 1/4-40 NS screw moves the mag .025" per turn, .004" per hex flat etc. Any shim adjustment needs the shim pack relaxed to change it, which means you move the mag more than really needed. A screw only makes the adjustment. On the other hand a shim pack with a roll pin or safety wire through it will not move or get lost from vibration.
Ideally, the screw should have a "mushroom" head or swivel foot like a Porsche adjuster so as not to crater the mag where it touches, or it should elevate a wedge block from below so only the block contacts the mag. It could also advance a wedge deeper from 90° laterally, but now the contact area will be smaller and will rise as the wedge presses in. etc.

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