1996 Ski-Doo Shop Manual, Volume 1, Page 97Get this manual
Se ion EN GI Sub-Section 02 (377, 443 AND 503 ENGINE TYPES)
ENGINE TYPE 377 503
RING COMPRESSOR PN 420876090 420876970
NOTEThe ring compressor will not fit on over size pistons
3,4,6, Cylinder Head, Cylinder and Intake Socket
Check flatness of intake socketsRefer to ENGINE DIMENSION MEASUREMENT 04-03 and look for checking surface flatness, At cylinder andor cylinder head installation, use aligning tool or exhaust manifold itself to ensure sealing of intake manifold and exhaust before tightening cylinder head nutsALIGNING TOOL ENGINE TYPE PN 377, 443 and 503 420876171