Servicar timing mark location different for auto advance and manual timers?

[Buster]

I am setting timing on 1956 Servicar with kick only and later model auto advance timer. Harley manual for 1959-73 servicar on page 5F-3 says for manual advance timer the timing mark should be half way between front of window and middle of window. Says on page 5F-5 for auto advance to set timing mark in middle of window. Why is the timing more advanced with auto advance timer then with manual timer. Where should the mark be in my window be with kick starter and auto advance timer.

[Rubone]

You are way overthinking this....

[T. Cotten]

With the old static method, Buster,...

Gear lash and other weird things make it actually come out slightly retarded, so the manual prescribes setting the line advanced in the window.

But when the auto-advance was introduced, the prescription became a strobe, and then the line really was in the middle.

So when initially setting up an auto-advance by the static method, the line should be rearward in the hole, and then dynamically fine-tuned to the middle with the strobe.

....Cotten
PS: Kitabel once pointed out that it is really an auto-retard.