running lean

Hi Guys,
I need some expert opinions.
Can anyone tell me exactly what the bypass and volume screws do on a standard 75L Bug carby,I want to try running a bit leaner to get better fuel economy,I've followed the manual but it does'nt actually say if clockwise is leaner or richer,and inside the tailpipes looks a bit black(rich) .
Also can running leaner do damage?
Go roosters !!!!!!!

yes - running lean can be bad.
Lean = hot = damage

Regardless

in is lean
out richens

you should have a 34 Pict 3 carb onyour car
tune by this procedure
http://www.vw-resource.com/34pict3.html

If you are really keen - get your car dyno'd or at least get an analyzer put on your tail pipe

Best economy is tuned spot on, not lean, not rich. If the motor is tuned to its optimum then it is giving the most power available from a given measure of fuel, least thats the way I see it.

Also I don't think the colour of the exhaust pipes makes much difference since leaded fuel went out of the window.