Adjust A Harley Drive Belt

Harley Davidson belt drives are highly engineered and effective drive systems. They are extremely quiet and immune to the corrosion due to their fiber/polymer materials. They require no lubrication and resist stretching and wear from the enormous loads placed upon them by the engine. Belt tension and rear axle alignment are the main concerns when adjusting the belt, and these conditions are easily checked with a few inexpensive specialty tools.


1. Break the torque on the rear axle, but only loosen enough to relieve the clamp pressure at the swingarm and allow the axle adjusters to move the axle. Place the transmission in high gear.

2. Check axle alignment with the alignment tool. Locate the factory-drilled hole in the swingarm. It will be about eight inches forward of the axle and on the outer face of the swingarm tubing. Insert the short end of the alignment tool into the hole and orient the tool so that it points to the rear of the bike along the swingarm until it intersects the axle. Slide the rubber O-ring on the tool down to exactly where it intersects the precise center of the axle. This is very important to the accuracy of the procedure.

3. Carefully remove the tool from the hole and transfer it to the other side of the swingarm, being sure to not disturb the O-ring and lose your measurement. Insert the tool into the new side and check the position of the center of the axle against the rubber O-ring indicator. The O-ring should fall out exactly as it did on the first side. If there is any difference, then tighten or loosen the axle adjuster on the second side until it matches the position of the first side. The axle is now aligned and an accurate belt tension test may now be made.

4. Locate the graduated sight window on the belt guard. If the model does not have a sight window, brace a machinist’s rule against the swingarm and use the index slider to indicate the current position of the belt where it intersects the rule. Place the belt tension tool onto the bottom of the belt, close to the sight window. Push up on the tool until it indicates exactly 15 pounds of pressure on the belt. Observe the sight window or the machinist’s rule and note the amount of deflection, in fractions of an inch (not thousandths). Refer to the factory specification for your year and model of bike to determine if the belt tension is correct, tight or loose.

5. Adjust belt tension at the axle adjusters. Tighten the adjusters on a loose belt and loosen them on a tight belt. Turn the adjuster nuts exactly the same amount, and adjust both sides before attempting to test the belt deflection. Check the axle alignment after each adjustment or you may get a false tension reading or worse, introduce a bad rear axle alignment issue into the equation.

6. Torque the rear axle to factory specification for your model of Harley and check the axle alignment one last time before attempting to test-ride the vehicle.