I had to do some work on my carb. My AP nozzle was damaged so I made a new one. I guess I went into the part of the carb you are not suppose to. Anyways I noticed the small gasket which seperates the ap system, the pilot air jet and the main air jet was also damaged, factory problem! I had to cut a new gasket from viton and put it back together. Kiehin does not support that part of the carb & will not sell a gasket for it. Slapped it together and also replaced a the top end(Weisco piston) and went riding. Broke it in for an hour and did a hard 17 mile loop, the bike rode great. Washed my bike and took it out the next weekend and could not ride. It would start with the choke but sound terrible and when I push in the choke it would barley idle and if I gave it gas it would die. I also noticed alot of smoke from the exhaust. I tried adjusting the pilot air screw but to no avail. Oh yeah I own a YZ 426f and has a FMF Q. Took the carb apart three times after the problem and everything looks clean the one concern I have is that small gasket. I am stumped! Can anyone help.