94 ZR580 with 4200 miles on it, cleaned carbs,new plugs, startes and idles fine, let warm up and get going, take off is good then starts to bog down and acts like a plug is fouling, have to feather throttle to keep running. set the air/fuel mix at 1 then 1 1/2. still doing it. Has good spark. Could this be electical or is it carbs? any suggestions.