2003 Ski-Doo ZX Series Factory Shop Manual, Page 119Get this manual
Subsection 02
Section 04 ENGINE (377, 503 AND 552 ENGINE TYPES)
Cross torque cylinder head nuts nos1 and to 22 Nm (16 lbfft); torque each cylinder head individuallyInstall armature plate, fan housing and then air deflectorInstall gasket on each side of the air deflectorTorque intake socket bolts to 22 Nm (16 lbfft)552 Engine 12, Reed Valve Blades have curved shapeInstall with their curve facing reed blockWith blade stopper no13 removed, check reed valve for proper tightnessThere must be no play between blade and valve body when exerting finger pressure on blade at blade stopper locationIn case of play, turn blade upside down and recheckIf there is still play, replace blade andor valve body