if the decompresser is ruled as the problem a standard spark plug fits strait in the hole and does not impede the operation at all. the terminal on the end is the exact right size for the rubber hose to slip over
the decompresser in victas are of poor quality because the diaphragms often perish and eventually do not open and close the valve as it should because of vacuum loss.
i have had a few old Tecumseh engines with crankcase mounted reed valve assemble and some weren't to bad. the difference between the good and bad ones were one had a totally flat assembly with all the valve on one plain but the other had a triangular shaped assembly that meant it had about twice the surface area and therefor more valves so it sucked freely and closed quicker because the valves were physically smaller. the smaller valves allowed sharper acceleration and response, and also let more fuel in easier when cold starting. i might take a pic of the two different types if you like.
regards jay
