I was busy getting ready for the visit of a daughter this past weekend and forgot I hadn't posted the results of the running tests I made after getting a replacement battery for the tachometer on my modified distributor tester.

After rebuilding and re-magnetizing the KNC1 it sparked reliably down to 160 rpm (320 rpm engine). I then stuck a piece of reflective foil to the chuck on my lathe and used a non-contact tachometer to check its speed to know how the magneto had performed immediately after rebuilding, but before re-magnetizing. The 300 rpm on the uncalibrated lathe dial I had found for my previous post turned out to be 315 rpm (630 rpm engine).

As I wrote previously, a Lucas manual says 300 rpm (engine) is at the low end of kick starting speeds, with 500 rpm normal. So, the magneto is now performing up to its full, um, potential.

The 320 rpm vs. 630 rpm is actually a significantly bigger difference than I usually see before and after magnetizing. This means this particular magneto had become significantly demagnetized prior to ending up in my hands. However, even had the "professional restorer" not used an inappropriate capacitor that failed, these results illustrate how much performance can be lost if a magneto of unknown previous history is not properly remagnetized after rebuilding. The fact it worked at 630 rpm (engine) means a healthy guy could have gotten an engine running with it, but probably would have incorrectly blamed its lousy performance on being intrinsic to magnetos. It had been "professionally restored," after all.

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