It helps to round off the sharp edge of each end of the pin. It may also
help to reduce length by a tad. Smoothing pin over its length with abrasive paper may also help. Pins do get bent ever so slightly and
become difficult to remove or reuse.
I believe prewar KB4 twin would have had the 7 slit water pump and
the 3 element clutch with one pin. If run without the clutch with the
propeller directly engaging the sheer pin, there is need for a short pin
to drive eccentric cam PLUS a spring clip in the groove to retain the
drive pin.
Length of sheer pin or clutch drive pin can be gauged by
length of slots in propeller or metal clutch disc
Length of oscillator drive pin (for 7 slit version of oscillator cam) is diameter over pin hole less twice depth of groove.
Hope this is clear enough to follow.
Louis
