Hi, can anyone help me...I need to identify what spark plug to use on my freshly rebuilt Firefly engine 1933. I have been told Champion D9's will fit but the problem I have is that there is an 18mm initial hole and then at the base is a smaller diameter non threaded hole. It appears that the plug should reach as normal down the threaded part and then that would mean that the electrode would sit within that last hole and would not protrude into the chamber...maybe that is correct? I have a good photo of the Plug hole that shows my issue but I cant post it as I don't know how to load it onto the web. Shame we cant just drag and drop images into this forum.
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