Carburetor adjustments are simple- - - -always have been, always will be. People who say otherwise need to come talk to my garden in the springtime and I'll save a bundle on fertilizer costs. There are two adjustments on a stovebolt carb regardless of what brand you're working on- - - -idle mixture and idle speed. The idle speed screw is the one that speeds up or slows down the idle- - - -it's on the lever that moves when you step on the gas, or maybe on the carb housing next to that lever. Turn it clockwise to speedup, counterclockwise to slow down. If you're got a digital watch, get somebody to explain the CW/CCW concept to you! Set the idle speed somewhere in the 500-700 RPM range. Doing it "by ear" right now is fine- - - -we just don't want the engine stalling or racing.
Now- - - -idle mixture- - - -that's the screw sticking into the carb body near the bottom. It's a short screw with a spring around it, and nothing near it is going to be moving. With the idle speed set somewhere near "normal" speed, start turning the mixture screw clockwise until the engine slows down, stumbles, or tries to stall. Back the screw up until the engine runs smooth and steady. Go just a bit further CCW (maybe 1/8 turn). readjust the idle speed if necessary to get the best idle speed and smoothness.
It takes me less than a minute to adjust most carbs, with NO test equipment whatsoever. If you've got a tachometer, a vacuum gauge, and maybe a 4-gas exhaust analyzer, you can charge your customer a whole bunch of money to do the same procedure I just described, and impress him/her with your alleged "knowledge" of carburetors. Tuneup "specialists"have been using procedure #1 for as long as I can remember, and getting just as good results as the guys do who have a shop full of equipment. No external adjustments on 99% of the carbs out there have ANYTHING to do with high speed mixture or gas mileage, no matter what the self-styled fuel system gurus claim!
Jerry
