X2, check your valve lash,
from the owners manual,
Valve clearance with valve springs installed and piston 1/4in. (6 mm) past top dead center (check when engine iscold)..Intake0.004 − 0.006 in. (0.10 − 0.15 mm). . . Exhaust0.004 − 0.006 in. (0.10 − 0.15mm)