What are things I should try and check to figure out why my 98 YZ400F won't idle? I have ordered new gaskets for the exhaust, valves are not too tight, cleaned carb, stock jetting, stock exhaust, 93 octane, hot start valve works properly. I've just plain run out of ideas. Tried tuning with the pilot screw with no luck. Is there something that I'm missing in the carb? Any ideas anyone?