My 2002 426 is having a difficult time idling lately. Have to keep blipping the throttle to keep it running. Any ideas on where to start to correct this? Bike has very low hours. Am going to put a new plug in it, and clean the air filter(only one 2 1/2 hour ride since last cleaned). Is the black plastic turn knob the way to adjust the idle (looked in my Clymer manual, but it's pretty worthless)?