1990-1998 Arctic Cat Snowmobiles Repair Manual, Page 140Get this manual
CHAPTER FOUR
3Check the specifications listed in Table and note if there are changes suggested for the operating altitude4If changes are recommended, begin by making these changesRefer to Chapter Six for carburetor removal and installationCAUTION The engine can be damaged by operating without the air intake silencer installed even while tuningAlways reassemble the snowmobile while testingWARNING lfyou are taking spark plug readings, the engine will be HOT! Be careful whenever any fuel is spilled, such as when the main jet cover is removed from the bottom of the float bowlSpilled fuel is an extreme fire hazardHave fire extinguisher and an assistant standing by when peiforming this procedure
Reading Spark Plugs