Air mix

[andrewmill]

How do you determine the correct air mix.
I know you adjust withe screw in air filter.
Is there a rev to set to, or idle speed.

[gpowell]

Just read this, hopefully you are sorted.

The air mixture screw is on the back of the carb and accessed from the back of the engine. Depending on model it can be (early type) a slotted screw accessed via a grommet in the carb box or (later type) a via hex head screw in the same place.
I always set them at 2 and a quater turns out and adjust from there.
Get the engine warmed up and set the tick over via the sprung screw through the air filter.
Once you are happy with tick over not to fast not to slow mive to the air screw adjusting 1/4 turn at a time inward and see what effect it has on the engine. In will weaken out with richen. Ive always found 2 to 2 and a quater to be okay