Check to make sure that the carb slides are in correctly. Take off your air filters or box, and make sure that you can see the cut away side of the slides. Next check the jets in the side that isn't firing correctly. Make sure that they are clean and free of obstruction, all of them! Also make sure the float level is correct. I had the same problems as you just yesterday. It turned out to be that the slides were in the wrong carbs and the pilot jet on the right side carb kept getting plugged up, causing it to not fire. DO NOT EVER clean your carbs with a Q-tip! Good luck man, don't give up,
Ryan