Who is Ralph? Was he converting these engines?
I finally got the nerve to try and pop the unit off with a puller, and it worked. What I thought was a circlip was just the keyway.
So now I wonder if I can melt or drill out that old hall sensor and install a new one, or if I should start from scratch and discard the old unit.
Or if I should convert to gas/glow as seen here?
http://www.rcuniverse.com/forum/m_8009384/tm.htm
Gas/glow seems the easiest/cheapest. But then I will be dragging three types of fuel to the field. Iv'e never run EI or gas/glow. I've just been using the magneto on my other engines.
So it appears this is an old 21cc Echo from the 80's, and was converted at some time very profesionally. I guess my preference would be to re-use the original mechanical timer, but that may not be practical. Thanks.

Rod S