If the screw is on the air filter side (relative to the venturi,) it meters air (in=richer, out=leaner.) If the screw is on the intake side, it meters fuel (in=leaner, out=richer.) So on a phva, the screw richens the fuel mix if screwed in, and out=leaner fuel mix.
> pat splat Wrote:
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> u can richen the low end w your needle height. and adjust your throttle
> slide till it idles. i always forget which way is richen and lean on
> that screw.