Now hold on.....

Maybe the bottom end mix is too rich and the top end mix is fine.

I can't comment on adjusting this since I'm not sure whaty does what on that particular carb.

If the mixture screw is for the idle mixture or low end, go ahead and make it a LITTLE BIT leaner. Don't mess with the top end (needle)

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If it ain't broke, and you mess with it long enough, it will be.