1985 Ski-Doo snowmobile Service Manual, Page 153Get this manual
Section 02 ENGINE Sub-section 07 (503 ENGINE TYPE)
CLEANING
Clean all metal components in non-ferrous metal cleaner
16,17, Cylinder cowls
A gasket must be placed on both sides (inner and outer) of intake and exhaust holes of cylinder cowl
DISASSEMBLY AND ASSEMBLY
13, Fan retaining nut
To remove or install fan pulley retaining nut, lock fan pulley with special holder wrench (Use tool PIN 420 876 355) At assembly, torque not to 65 N.m (48 Ibf.fti
WARNING: If fan protector is removed, always reinstall after servicing