Kartjockey,
Is that compression release stock on early models or did you install it?
My 56M has the hole in head (un-taped) as all I have seen have.
I think I still have one I never installed. If I can find it I will put it in mine.
The one I may have has the same threads as a spark plug.
Does it give you a little braking power as the old 2-strokes from the 60s did.