"By jet adjustment knob, do you mean the mixture adjusting screw on the bottom of the carbs? and to richen the mixture do I screw in (clockwise) is this what you mean by down?"
Yes that is the screw/knob I mean. Looking up at the botton of the carb, if you turn the screw/knob clockwise you will lean out the mixture, In your case you will want to turn the screw/knob counterclockwise to richen up the mixture.
But first make sure your idle speed setting isn't too low. When the choke is on, there is a fast idle cam that speeds up the idle. See if reseting the idle speed doesn't solve your problem. To speed up the idle you will turn each idle screw an equal amount in a clockwise direction.
Then if that doesn't help, set your mixture by the book, in other words lifting the piston a small amount and seeing what the engine does. You do have a manual right? or do you need further help?. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif