Having difficulty with rebuild of my M-S carb. I "assume" it's original(?) to my '52 8N. It is a "B" type carb and has a brass tag permanently attached to the lower bowl that is deeply stamped "649" but I don't see any reference to that number as being applicable for various available rebuild kits. There is also what appears to be a lightly etched marking that may be 23 or 33, the lower part of the first digit is no longer visible. I've fully (I thought) stripped and thoroughly cleaned the carb only to discover one last orifice in the bottom of the bowl that was not visible prior to cleaning. It is located where the tip of the Power Adjusting Needle would engage it. It does not appear to have screw driver slots in it. My questions are: Does anyone have an idea what the "649" indicates? and Is this orifice removable/replaceable since the 2 kits I have don't appear to include anything that appears to be this orifice? Thanks