1978 Ski-Doo Shop Manual, Page 149Get this manual
SECTION 04 SUB-SECTION 02 (ENGINES)
to To remove rotary valve shaft assembly from crankcase special puller is needed(See Tools Section)First remove circlip then position special puller over shaft bore and screw puller bolt into rotary valve shaftWhile holding puller bolt, turn puller nut clockwise until shaft comes out