Tractor Repair: carburator adjusting, optimal operation, carburetor

Question
Hello, I have a 1948 John Deere A with model 53 carburetor.  How do you know when it is adjusted correctly.  I had it off and the settings got changed.  It starts and seems to run fine, but I would like to have it set for optimal operation.

Answer
 Hello,

  As a starting point, turn the screws in all the way just till they stop, do not tighten them.  Then back them out 1 and a half turns.  Run the engine till it warms up, then turn the idle mixture screw slowly in and out until it idles smoothly with no smoke.  Then run it  full throttle and adjust the high speed mixture screw until it runs the smoothest with no smoke.  If the engine sputters a little under load, back out the high speed screw a little more.

                  Arnie