582 idle rpm is too high

I am not sure why you want to idle it lower without a load on it but if it is a must do then you need to start with a slide that has less of a cutout. That will require changing all of the other metering components to match the slide. 

I made the above statement assuming that the 582 is installed in an aircraft as it was designed for. That you have the cables adjusted with freeplay at idle and that you are jetted according to the Rotax charts. If all is as it should be then richening the idle circuit will probably reduce the idle rpm. 

Thanks Dennis. Yes, all the parts and jetting is original and according to Rotax guidelines. I dont necessarily want it to idle lower without load but I wasn't sure that with load the idle will decrease... The engine is installed in a dune buggy. When I attach the CVT , on neutral gear the idle will drop due to this load?

I have found that setting the idle screws by turns out is always inconsistent on anything other than a new carb.

This is due to the contact point on the slide wearing. Its a soft aluminium material.

Screw the idle screws out, use a 7mm drill shank as a guage and turn screws in raising slide until the drill shank fits snugly under the slide on both carbs.

You will find that the idle screws are in slightly different positions but the slides are in exactly the same position. Idle will be at or very near 2000rpm