My bike has developed a hesitation as I come off idle. It only lasts for a few seconds, and goes away at abt 3000 rpm. Could I have a vacuum leak or gummed up fuel injector? I checked valve clearance, spark plug, and cleaned the air filter. It seems as if it is too lean, not getting enough gas. Otherwise, the bike runs great, and gets about 62 mpg. it is a 2005 an400 with 14,000 miles.