Drive belts on snowmobiles should be changed when the belts reach the minimum thickness listed in your owner's manual. Belts that are too large or too small will affect the deflection of the belt. Deflection is how much slack or play is in the top part of the belt between clutches. Each manufacturer has defined amounts of deflection recommended for its machines. Measuring the belts requires only basic instruments.
Remove the old belt from the snowmobile. Because this will be different for each brand of snowmobile, you should follow the instructions in the owner's manual. Remember how the belt is installed and make notes if necessary for reassembly.
Measure the outside diameter of the belt. Use a piece of string and wrap it around the belt. Let the belt rest naturally and do not squeeze it with the string. Record this measurement.
Measure the width of the belt. Use a tape measure to measure the width of the belt in a number of different places. Confirm the measurements with a caliper and record the measurement. The new belt purchased should be the exact same width to properly fit on the clutches.
Measure the inside diameter of the belt by turning the belt inside out and use the string and tape measure method from Step 1. Record the measurement.
Store the recorded measurements in a place where you can find them so you will not need to measure next time.
Install the new belt and check for deflection. Check your owner's manual to determine the allowable deflection of the drive belt. Take a straight edge and lay it on the belt between the two clutches. Measure the distance between the straight edge and the belt below. Adjust the deflection according to the specifications in the owner's manual.
- Old belts will be slightly larger because of wear on the belt over time. When purchasing a new belt let the sales rep know that your measurements were taken on a used belt.
- Periodically adjust the deflection as the new belt becomes stretched with use.
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