I too was running into the same problem you are having, one side firing while the other was not. Only mine was running on the left and not the right side. I fixed that problem yesterday actually lol. These guys are definitely pointing you in the right direction, it is most likely in your left carb. I found that taking the mix screw, spring, washer and o ring completely out, and then squirting some cleaner thru the holes, followed by compressed air, and also squirting carb cleaner thru the enricher tube followed by compressed air, then doing a bench synch on them fixed my problem. There are plenty of threads on here about bench synching, that got me pretty darn close on the synch. I think these guys have mentioned it already but that little tiny o ring under the washer, spring, and mix screw can cause ALOT of headaches if it is missing, broken, worn, etc. The bike will NOT idle correctly if it is. Take your laptop out in the garage with you, pull up the excellent carb cleaning guide from this site, go to the pilot circuit cleaning section and walk thru it step by step. That fixed my problem, and now my bike is running like a champ. Keep at it, the more you do the more you learn, Im living proof of that lol. Cant thanks these guys enough for all the help.