mixture screw on weber 40/s

[basil]

I have weber 40 carbs on my elan, on adjusting them, turning the mixture screw clockwise "in", is that weakening the mixture or ritchening the mixture as i still get dry black plugs !

[RichC]

weakens.
what plugs are u running?

[basil]

weakens.
what plugs are u running?

ngk bp7es, also tried ngkbp6es both at .65 gap !

[RichC]

too much fuel causes sooting . I've had this prob & it's now solved , except a tiny bit on plug 4.
cause of too much fuel could be any of following (but may be something less obvious that isn't listed) in order of likelihood in my limited experience with 40 DCOEs & worth checking first ....
poor needle valve seating
sticking needle valve
poor carburettor float level adjustment
blocked air filter
sticking choke mechanism
.... for starters!

[paddy]

Don't forget that the screws are only adjusting the idle mixture. The mixture when running is determined by the jetting, and could also be too rich as a result of other problems (eg fuel leaking through the accelerator pump jets).

Paddy