I have fixed the stop switch. I cleaned the connectors and gave it a spurt of contact clean in the gap between the button and the body of the kill switch module.
I also un bent a linkage that wasn't activating the choke properly, so it now starts without requiring starter spray.
With regard to overrevving, look under the carby and back, there are 2x phillips head screws. ignore the one closest to the motor, but screw in the outer one - this will lower top speed
I made the mistake of screwing in the second (black plastic) screw on the front of the carby itself and wondered why the lower revs raised, then re-read what you said and it finally clicked what you meant.
I used my electronic tacho for the first time since ordering it months ago and now have it maxing out at 3060 RPM. It must have been close to 6K before because when I first reduced it, I thought it was ok but was still too high doing 3700.
Engine now sorted. A very quiet smooth motor. Many thanks Tyler.
I had two V40s to choose from to work on but decided on this one as the other has leaked quite a bit of oil from the bottom (main seal it looks like) and all over the blade disc during prolonged storage.
