Content Source: 2021 550 Indy 144 Owner’s Manual (9931273 R01) > Maintenance Chapter

IMPORTANT

The Owner's Manual for this vehicle contains warnings, instructions and other information you must read and fully understand before safely riding or performing maintenance on this vehicle.Always follow the warnings and instructions in Owner's Manual.

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Spark Plug

Spark Plug Recommendations

It’s very important to use the correct spark plug for your machine. A spark plug with a heat range too high will cause engine damage. A spark plug with a heat range too low will cause excessive fouling and engine malfunctioning. Change the spark plugs every 2000-2500 miles (3200-4000 km)
NOTICE
A spark plug with a heat range too high will always cause engine damage if the engine is operated in conditions more severe than intended for that plug. Always use the spark plugs recommended for your snowmobile.
A new engine can cause temporary spark plug fouling due to the preservative added during the assembly process. Avoid prolonged idle speeds, which cause plug fouling and carbonization.
  • Use recommended spark plugs with the proper gap.
  • Use only resistor-type spark plugs.
  • Torque spark plugs to specification.
    TORQUE

    Spark Plug

    18-22 ft-lbs (24-30 N·m)
  • Always carry spare spark plugs.

Spark Plug Condition

Normal Plug

The normal insulator tip is gray, tan or light brown. There will be few combustion deposits. The electrodes are not burned or eroded. This indicates the proper type and heat range for the engine and the service.
TIP
The tip should not be white. A white insulator tip indicates overheating, caused by use of an improper spark plug or incorrect carburetor/throttle body adjustments.

Wet Fouled Plug

The wet fouled insulator tip is black. A damp oil film covers the firing end. There may be a carbon layer over the entire nose. Generally, the electrodes are not worn. General causes of fouling are excessive oil or use of non-recommended injection oil.

Spark Plug Removal and Replacement

Spark plug condition is indicative of engine operation. The spark plug firing end condition should be read after the engine has been warmed up and the vehicle has been driven at higher speeds. Immediately check the spark plug for correct color.
TIP
Incorrect fuel mixture can often cause a spark plug to appear too dark or too light in color. Before changing spark plug heat ranges, be sure the correct main jet is installed in the carburetor(s).
WARNING
A hot exhaust system and engine can cause burns. Wear protective gloves when removing a spark plug for inspection.
  1. Remove the left side panel.
  2. Remove the spark plug cap.
  3. Using the special wrench provided in the tool pouch, rotate the spark plug counter-clockwise to remove it.
  4. Reverse the procedure for park plug installation.
    TORQUE

    Spark Plug

    18-22 ft-lbs (24-30 N·m)
  5. Reinstall the spark plug cap.

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