Snowmobile Polaris 120. Manual - part 14

52

ADULT SECTION

Maintenance

Spark Plugs

A new engine can cause temporary spark plug fouling due to the preser-

vative added during the assembly process. Avoid prolonged idle speeds, 

which cause plug fouling and carbonization.
Refer to the specifications section beginning on page 80 for recom-

mended spark plug type and gap.

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. Immediately check the spark plug for 

correct color.

Spark Plug Removal and Replacement

1. Stop the engine.
2. Remove the spark plug cap.
3. Using the special wrench provided in the tool pouch, rotate the 

spark plug counterclockwise to remove it.

4. Reverse the procedure for spark plug installation. Torque to 12-14 

ft. lbs. (16-19 Nm).

CAUTION

Using non-recommended spark plugs can result in serious engine damage. 

Always use the spark plugs recommended for your snowmobile.

WARNING

A hot exhaust system and engine can cause serious burns. Wear protective 

gloves when removing a spark plug for inspection.

53

ADULT SECTION

Maintenance

Spark Plugs

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 indi-

cates the proper type and heat range for the engine and the service.

NOTE:

The tip should not be white. A white insulator tip indicates overheating, 

caused by use of an improper spark plug or incorrect carburetion 

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, use 

of non-recommended oil, improper use of the choke, or incorrect carbu-

retion adjustments.

54

ADULT SECTION

Maintenance

Fuel Valve/Fuel Lines

Inspect the fuel valve and the fuel lines regularly. Carefully check the 

system's fuel line condition after periods of storage. Normal deteriora-

tion from weather and fuel compounds can occur. Replace any worn or 

damaged components.

Exhaust System

At approximately 50 hours, check the exhaust system for wear or dam-

age. To inspect, allow the engine and exhaust system to cool completely. 

Open the hood and inspect the muffler and pipes for cracks or damage. 

Check for weak or missing retaining springs or damper/support grom-

mets.

WARNING

Hot exhaust system parts can cause serious burns. Allow adequate time for 

the exhaust system to cool. Never perform this procedure with the engine run-

ning.

55

ADULT SECTION

Maintenance

Carburetor

Proper carburetor adjustment is critical, since a mixture too lean (too 

much air, too little fuel) will result in overheating of the combustion 

chamber causing pre-ignition of the fuel. This results in piston burning, 

bearing failure, or complete engine failure. A lean mixture can be the 

result of fuel line restrictions, foreign matter in the carburetor, etc. A 

mixture too rich (too much fuel, too little air) is also unfavorable 

because it can foul plugs and cause generally poor engine performance.
All carburetors have been pre-set at the factory for adequate fuel supply. 

Higher altitude operation may require different adjustment and settings. 

The number stamped in the end of the main jet indicates the jet size that 

was installed at the time of manufacture. For questions about optional 

jetting for conditions in your area, see your Polaris dealer.
Correct setup provides engine RPM within its given power band at full 

throttle settings and also provides maximum efficiency and operation at 

all other throttle openings. See your dealer for carburetor adjustments, 

which may include the following:
• Carburetor component changes for specific altitude and ambient tem-

peratures

• Choke adjustment
• Air screw settings (if applicable)
• Idle RPM adjustments
• Throttle safety switch inspections and service
• Throttle block-to-throttle flipper clearance adjustment

CAUTION

Improper carburetor adjustments can result in safety hazards as well as seri-

ous engine damage. We recommend that all carburetor adjustments be per-

formed by your Polaris dealer.