Preunit 650 ignition timing,K2f magneto,without opening side covers.

I have been timing my old '52 this way for decades.
It is very simple compared to opening / removing timing side cover or primary being I don't have any other access to the end of the crank to get 38* BTDC.
Years ago I triple checked to see if 3/8" BTDC was truly 38*,and it was,right on the money.
Enjoy,and I hope this helps you.