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Engine started over revving to the max. Replaced faulty primer bulb and ageing governor springs but still overrevving. Any ideas would be appreciated.

Your governor is broken or something is jambing it.
2 types of governor air vane & mechanical which one do you have

Its mechanical.

Start the engine and push the governor arm open & closed you should feel the tension changing.
As it is the mechanical type also check that the arm is tight on the shaft.
If not reset the governor.
If the arm is tight to the shaft and there is no obvious change in the tension of the governor then it is safe to assume the governor is kaput.
Never seen one like that on one of these but then again I have never seen a lot of things.