Thread: Ajusting a carburetor

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I was reading in a book about ajusting the idle mixture ajusting screws. It said to trun out until engine runs fastest and smoothest. And then back in to specified lean drop level. What are they talking about? Thanks, John.

Originally posted by Johnwalkeasy
I was reading in a book about ajusting the idle mixture ajusting screws. It said to trun out until engine runs fastest and smoothest. And then back in to specified lean drop level. What are they talking about? Thanks, John.

I can't explane it to you john, I knew what it was 30 yrs. ago, but if you had a rebuild kit or all of you carb. spec. it would have a lean drop level setting for it. A good rule of thumb is after you get your hi rpm setting I always adj. the idle screws back in about 1/8 of a turn and let it go.

Lean drop is when you start rich, say 4 or 5 turns out. Then you turn the screws in about 1/4 of a turn at a time untill you reach your highest idle speed. Then turn each screw in until it drops 20 rpm. A total of 40rpm. One idle screw may be out more than the other. This is ok as there is a difference between needles and seats. Throttle plates must be adjusted also.