Actually, decompression valves are not hard to clean up (especially if you have two) and will help start the engine much easier (especially when you are trying to work with ignitions, they lead to a stronger spark, and help prevent flooding)

I would strongly recommend restoring the decompression valve.

The 3rd engine sounds like a Series 70 MKIV, with a G4 carby.

Cheers
Ty

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