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 TestInquiries to Rider
Each rider reacts to problems in different ways, so it is important to
confirm what kind of condition
the rider is dissatisfied with.
Try to find out exactly what problem occurs under exactly what
conditions by asking the rider; knowing
this information may help you reproduce the prob ...
Piston Ring Groove Width Inspection
Measure the piston ring groove width.
Use a vernier caliper at several points around the piston.
Piston Ring Groove Width
Standard:
Top [A] 0.82 0.84 mm (0.0323
0.0331 in.)
Second [B] 0.82 0.84 mm
(0.0323 0.0331 in.)
Service Limit:
0.92 mm (0.036 in.)
Second 0.92 mm (0.036 in.)
...
Swingarm Removal
Remove:
Rear Wheel (see Rear Wheel Removal in the
Wheels/Tires chapter)
Mud Guard with Rear Brake Hose (see Mud Guard Removal
in the Frame chapter)
Rocker Arm (see Rocker Arm Removal)
Remove:
Brake Hose Clamp Bolt [A]
Unscrew the swingarm pivot shaft nut [A].
Usi ...