Chris you need to remove the brass jet block from each carburetor which sometimes you can do without removing the carb from its manifold. Then at the front lower side of the jet block you will see a hole about the diameter of a match head, at its base is a tiny hole (use a magnifying glass to see better) this is the idle circuit fuel passageway. It is either 1......too small a drilling size, or 2 ......it could have tiny amounts of swarf in it. Either way, if you use a number 76 drill which is around 18 thou diameter from memory in a small "Pin vice" like an alloy pen that has a tiny chuck to hold the small drill bits, then spin this carefully into the hole, and open it out slightly larger then blow through with compressed air and reassemble the block back into the carb body. You should be able to achieve a setting around the normal 1 to 1 and a 1/4 turns out from the needle seated position. Sometimes I have found the carb is not a tight fit on the manifold stub either and it clamps up ok with the pinch bolt nipped up, but it can still leak air past the joint. Sometimes if this is the case, the mixture screw will still need to be wound fully in to achieve a good idle on that cylinder, but you are better off to slip the carb off the manifold and use some sealant being very careful that the excess does not block the tiny idle circuit passageway on the inner side of the slide. I usually remove the slide all together and wipe away the ridge of sealant with my finger down the mouth of the carb. Let the sealant harden, reassemble, and your settings should return to normal. Make sure with your drill size that you "Do not" go above a drill larger than .020" as this will become too rich. Cheers..................Greg.
