richen the low speed needle on the side of the carb.....usually locacted on the right side of the caarb on the end of the slide....when the low speed needle is too lean it will idle up and run hot or lean not good ....fatten the fuel mixture on the bottom and like kx 250 said make sure the idle screw is set so that when the brakes are applied that a 1mm gap remains inside the carb where the slide seats itself against the side of the carb......setting the idle screw can be done visually with the car not running...i suggest setting the lsn by starting the car warming it up and when the car begins to idle fast adjust the lsn by turning counter clockwise until it idles back down to an acceptable idle rpm......