1978 Ski-Doo Shop Manual, Page 148Get this manual
$ECTION 04 SUB-SECTION 02 (ENGINES) Using angle finder, mark crankcase at 1270 from bottom edge of magneto side inlet port
ROTARY VALVE MECHANISM
CLEANING
Discard all oil seals and "0" ringsRemove crankcase sealant traces .on rotary valve gear, adjacent bearing and on end cap sealing surfaceClean all metal components in non-ferrous metal cleanerMARK HERE
DISASSEMBLYASSEMBLY
(2)At assembly, apply crankcase sealant (l.octite 515) on rotary valve gear and bearing mating surfaces
From top edge of magneto side inlet port, mark crankcase at 48 0
Disc valve adjustment with replacement crankcase
having no timing marksTo correctly install the rotary valve disc proceed as follows:Turning crankshaft counter-clockwise, (drive pulley side) bring magneto side piston to Top Dead Center using T.D.CgaugeREQUIRED TOOLS