no were not talking about the carb. were talking about the ignition timing. The a12 has a helpfull set of cast numbers on the block beside the belt running from the crank to the alternator. put a strobe light on it (the belt next to the numbers) and it will tell you the timing in degrees. to adjust it loosen off the distributer and at the bottom there is another set of numbers +5 to -5 (i think) and you can move it which ever way you need to get the right timing. 7 degrees is the best for a a12. NO need to go more unless youve done something major to the motor. if you move the dist. while the motors running youll hear the difference in the timing.