James,

These things are generally in two groups: the three screw group and the
two screw group.
Let's take the two screw group first. You'll need a screw driver and a
spray can of starter fluid (ether). The two screws are a mixture screw (the
needle valve) and an idle speed adjustment. Screw the mixture screw all the
way clockwise and then back out 1 1/2 turns. Give it a shot of starter fluid
and start it. Adjust the idle speed if necessary so that it runs at idle.
Let it come up to operating temperature. Now adjust the mixture screw
counterclockwise (you enrich the mixture). It should begin running quite
well at some point, continue adjusting the screw ccw and it should begin to
run rough. Note this position. Turn the screw cw (you lean the mixture)
until the idle becomes rough. Note the position. Usually about half way
between these two positions is the proper adjustment. You may need to fine
tune slightly. Now that the mixture is set adjust the idle speed screw by
reducing the engine speed at idle until the engine almost stalls. Increase
the idle speed slightly above this and you are done.
A similar process is used in the three screw group . There is a low speed
mixture, a high speed mixture, and an idle speed screw. Screw both mixture
screws in all the way,cw, then out 1 1/2 turns, ccw. Give it a shot of
starter fluid and start it. adjust the idle speed if necessary so that it
does not stall. Let the engine warm up. Now adjust the low speed mixture
screw as described in the above paragraph. Adjust the idle speed screw as
described above also. Now set the engine to full speed and adjust the high
speed mixture screw as you adjusted the low speed screw. OK, the two mixture
screws interact slightly so you now need to repeat the process of finding
the points at which the mixture screws cause rough running and setting the
screws half way between these points.

Good luck,
Dave M.