The jets have absolutely ZERO to do with idle mixture. Nothing, nada, zilch. They are on the power circuit, which comes in well above idle. That list number is a 650 spread bore, vacuum secondary carburetor. They are really decent carburetors and can deliver a great mix of power and mileage. I would not suspect the carburetor RIGHT away. Where is your initial timing set? If it's not advanced enough, that will cause it to run rich at idle. That's the first thing I would look at.