1982 Ski-Doo Shop Manual, Page 134Get this manual
SECTION 02 ENGINE SUB-SECTION 07 (640 ENGINE TYPE)
Remove any burrs from piston caused through circlip installation using very fine emery cloth
Piston notch -t1'-1f1-':;j
Circlip break
NOTE: Refer to Technical Data for component fitted tolerance and wear limit
eD G) When installing cylinder andor cylinder head, the cylinder aligning tool must be used to ensure sealing of intake manifold and exhaust(See Tools Section) Install muffler on exhaust socket then install aligning barCross torque cylinder head nuts to 20 N-m (15 ft-Ibs)