When the engine is running, the air intake valve is lifting up.
If the valve does not operate properly, check the air intake solenoid valve hoses for leak.
If there are no leaks, check the air intake solenoid valve.

Air Intake Solenoid Valve Unit TestCamshaft Removal
Remove:
Cylinder Head Cover (see Cylinder Head Cover Removal)
Crankshaft Sensor Cover (see Crankshaft Sensor Removal
in the Electrical System chapter)
Using a wrench on the timing rotor bolt [A], turn the crankshaft
clockwise until the line [B] (TDC mark for #1,4 pistons)
on the timin ...
Clutch Cover Removal
Remove:
Right Lower Fairing (see Lower Fairing Removal in the
Frame chapter)
Clutch Cable Lower End (see Cable Removal)
Clutch Cover Bolts [A]
Turn the release lever [A] counterclockwise as shown,
and remove the clutch cover.
About 90В° [B]
...
Subthrottle Valve Actuator Inspection
NOTE
Be sure the battery is fully charged.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Turn the ignition switch to ON.
Check to see that all the subthrottle valves [A] open and
close smoothly.
Turn the ignition switch to OFF.
I ...