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NU4

The NU4 was a simple lowcost product designed for small four cylinder engines and found a lot of use with the Model T Ford. It used no timing gear, rather a loop wound secondary and double segmented collector spool that fires two cylinders every 180 degrees with one in the compression/ignition mode and the other a redundant spark during the exhaust stroke. they suffered from the usual woes of a shuttle wound design and inmsulation seepage. The wires were fastened to the brush holders by a tiny metric screw that lives under the brush spring and is often rusty and seized. Brush holders are often missing from the magneto.  When in repair they probably worked well and had fewer moving parts than most of the day. Here is some information to keep yours well.