1971-1973 Arctic Cat Snowmobiles Factory Service Manual, Page 29Get this manual
ENGINE SERVICING (SINGLE CYLINDER) GRotate the crankshaft counterclockwise until the indicator needle passes the specific setting (.026")Slowly rotate the flywheel clockwise until the continuity light brightensAt this point, indicator needle should read specific setting (.026")NOTE: The "F" mark and the timing mark in the crankcase should now be alignedCover housing must be removed to see timing marks13If dial indicator method was used, remove, using the following procedure: ALoosen the thumb screw holding the dial indicator in the adaptor and remove the adapt-
orBRemove the adaptor from the spark plug hole
Install the spark plug or replace with new plug and set the gap at .020"Connect the spark plug lead wireInstall the auxiliary starting pulley on the flywheel