Hey all,

As I mentioned in my other thread, "stupid idle screw.." I have been trying to adjust my Zenith carby.

The manual I have gives a procedure for adjusting what it refers to as the "vacuum prop valve"
That is the assembly that was in the way of my idle screw.

Does anyone know what it actually does??
Mine seems to do nothing as I cannot adjust it as per the manual.
The manual seems to imply it operates a butterfly valve but doesn't say what its purpose is.


Thanks
Ash