1970-1979 Ski-Doo Snowmobiles Service Manual, Page 133Get this manual
CHAPTER SEVEN
bOn aluminum chaincase models withouf external adjuster, release springs securing tensioner blocks (Figure 19)cOn models with aluminum chaincase and external adjuster, loosen adjuster bolt10Remove cotter pin and remove nut and washer from upper sprocket shaft (Figure 20)11Hold upper sprocket and chain and remove driven pulley (Figure 21)NOTE: On models equipped with pressed steel chaincase, wire sprocket to top of chaincase to prevent chain and sprocket from falling to the bottom of the chaincase