Tighten A Harley Primary Belt Drive

Adjusting the primary belt on a Harley-Davidson motorcycle can be a matter of safety.

As a Harley-Davidson is ridden, the drive belt will naturally begin to relax and loosen. As part of the pre-ride inspection, it is recommend that the belt tension be checked and adjusted if necessary. Completing this check regularly will prolong the belt’s life and enhance rider safety. The average rider can easily check and adjust the belt in just a few minutes. These instructions are based on a 2007 Softail, but other models are similar.


1. Move your motorcycle to a flat, dry surface. Using the belt tension gauge, check your belt tension with 10 pounds of force. Compare the belt position with the index marks on the belt guard. The belt should move between 1/4 of an inch and 5/16 of an inch. If your belt is within this range, no adjustment is needed. If your belt exceeds 5/16 of an inch of movement, proceed to Step 2.

2. Remove the spring clip from your rear axle nut with the needle-nose pliers and place to the side. Using the two adjustable wrenches, loosen the axle by turning the axle nut counterclockwise.

3. Following the instructions on your motorcycle lift, elevate the motorcycle’s rear tire. While this step is optional if you are on the road, it will yield better results and should be done if you can.

4. Locate the axle adjuster, which is forward of the axle and will be touching the axle. Using the 3/8-inch wrench, loosen the jam nut by at least 1/2 inch. Using the same wrench, tighten the axle adjuster by turning it clockwise. Repeat on the other side of the motorcycle. Using the ruler, check to ensure the axle adjusters are even on both sides. Tighten the jam nut.

5. Check the belt deflection as done in Step 1. If the belt is still too loose, repeat Step 4. If not, lower the motorcycle, tighten the axle and reinstall the spring clip. After 20 miles of riding check to ensure that all bolts are still tight.