Also, are your carbs synchronized? If one carb is hauling more air through than the other, you'll never get them tuned to work together. You need an air flow meter to know what each carb is actually pulling for air volume. I recently recalibrated a pair of 38's, one was pulling just over double the air flow, the engine ran like a bag of hammers. Just that change alone made purr like a kitten
This is what I use, the smaller one if I recall will fit everything up to 48mm. Shove it into the carb opening and adjust the rear carb to match the front.
The best carburetor syncronizing tool made for us to syncronize dual carburetors. Rather than measuring manifold vacuum via a restriction, it sensitively and accurately measures airflow WITHOUT RESTRICTION. This is the top quality GERMAN SK Gauge.
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