2002 vlx 600 running rich at idle. I have new plugs new air filter ,fresh oil and filter. I have pulled the carb and taken apart and cleaned. It still is running rich at idle you can smell it and if you rev it up black smoke comes out the tail pipes. I have tried adjusting the idle scew and you can screw it all the way in and it never dies. It seems to run allright down the highway. I have a service manual and I have tried about everything I know. Any Help?