I have a Speed demon 650ve which was tuned on a dyno but since I've taken it home when it warms up (20 min of driving) it surges really bad at idle and want to die. The idle is set at 500 in drive but will surge between 400 and 600, also you can see tons of white smoke ( running too rich?). I know absolutely nothing about carbs so I'm kindof at a loss right now.

 

It could be a number of things, but I would start off with some simple checks:

- If the cam has a fairly aggressive overlap and you are using a vacuum
signal to advance the distributor, I would suggest plugging that line at the
manifold/carb port.

This will eliminate any timing change due to manifold pressure variance.

Once you remove the vacuum advance (if installed), the idle timing and
RPM will change. You will likely have to increase the initial timing to about
20-25 degrees depending on what the motor likes. Check the total timing
at 3500 RPM to make sure it doesn't surpass the 36-38 degree range.
Based on your signature I'm going to guess the motor will want that much
advance, but you'll have to tune it for best results.

Try that and let us know if the motor stabilizes.

Do you have a vacuum gauge?