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mbrook

Ignition Wiring question

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mbrook
I hoping to get the wiring on my 12hp B&S right the first time. So I'm asking for some help. I haven't been able to find a wiring diagram for it. Its a 12 hp cast iron model #300420 series. I'm just looking for the ignition wiring. I have a wire coming from the points cover, one from my key switch and one from my mag/coil (I believe its the original mag/coil). Does the wire from the points cover connect to the block near the mag/coil under the air shroud? Then would the wire from the mag/coil connect to the wire from my key switch? Or do all three connect together?

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MadMike
I don't have my copy with me, but if you download your tractor manual from the Simplicity Tech Publications website, a wiring diagram should be included in the combined parts manual. I think. Mike

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Kent
Without knowing what tractor you have, I'd guess that the wire from the flywheel magneto goes to the points, and the wire from the ignition switch goes to the points also -- shorting out the points to kill the engine. At least that's how the old FDTs were wired...

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mbrook
The tractor its going in is my 3212V. I got the engine back from my cousin and put it in last night. After bolting it down and hooking everything up I noticed I had the white wire from the ignition not hooked up. I looked at the manual but could only figure its goes to the magneto. I talked with my cousin and he said he wired the points wire and the mag wire together on the screw under the air shroud. If all three wires are to be tied together then I should be able to just slice in the white ignition wire near the points cover. Right????

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Kent
I'm not sure that I would splice it "out in the open" like that, personally. I would run it into the points cover and connect it to the points, along with the one from the magneto. Some of the engines had a phrenolic (?) junction block that mounted on the block just above the points cover where the two wires connected. Having gone through the hassles of tracing a short in the wire from the switch (I accidentally pinched it putting on the dashboard & side tin), I'm kinda leery of the possiblity of shorting it out...

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PhanDad
My Homelite has a 12 HP Briggs in it; it is wired like the footdrager tractors Kent mentioned. Two wires come from under the shroud, one connects to the points inside the points cover; the other to the small bolt at the end of the "insulator" (a small piece of non conducting plastic, usually phenolic, mounted OUTSIDE the points cover using the top bolt for support - B&S part #66895). The white wire from the ignition switch connects to the small bolt also. The white wire should be ground when the ignition switch is in the "off" postion and inactive (no ground or voltage) when the igntion switch is in the "run" or "start" position. I believe both of the wires from under the shroud are connected together at the mag end. When the ignition switch is "off" the opening of the points doesn't break the ground circuit.

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HubbardRA
Do it as Kent said. That is the way most all of the magneto engines are wired. It should work fine. The only thing the wire from the switch does is short the points to ground to kill the spark and stop the engine.

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