I always find with the flat diaphragms like the green one ,if I put the throttle on full and hold the poppet valve out with the carby
off the engine and using long nose pliers to hold the poppet valve out then when I clip on the plastic diaphragm cover with the spring ,
the engine will only get to full rpm this way.
I think it's the flat black one that is the worst as they can shrink over time and don't allow much movement of the poppet ,
occasionally I have to replace them because I get full rpm but then there's not enough movement for it to idle.
The later black diaphragms are made a lot better with plenty of movement.
Parts below link.
https://www.outdoorking-forum.com.a...cta-g4-carburettor-governor-springs.htmlLink to modifications below if you wish to go that way.
https://www.outdoorking-forum.com.a...arby-repair-modifications.html#Post82288Don't forget to set the Poppet valve on C in the below pic, although some poppet valves don't have markings A B C
Cheers
Max.
