How to Replace a Belt on a Lawn Boy Self-Propelled Mower

If your Lawn Boy self-propelled mower won't drive when you pull up on the drive handlebar, you most likely have a broken drive belt that must be replaced. The drive belt wraps around the pulley above the blade under the Lawn Boy self-propelled mower deck and then around the transmission pulley on the rear axle of the mower. The repair isn't especially difficult.

Step 1

Pull the sparkplug cap off of the sparkplug on the front of the engine to prevent the mower from accidentally starting while you work on it.

Step 2

Tip the mower on its side so the gas tank is on top.

Step 3

Unscrew the transmission pulley cover screw with the screwdriver. Pull the cover off.

Step 4

Put the proper-sized wrench on the nut in the center of the tension pulley pressing against the belt wrapped around the transmission pulley. Pull out on the spring-loaded tension pulley to remove tension in the drive belt. Slip the belt off the transmission pulley.

Step 5

Slip the belt off of the pulley above the blade. Slip the new belt onto the pulley above the blade.

Step 6

Pull out on the spring-loaded tension pulley to allow the new drive belt to slide onto the transmission pulley with ease. Slip the new belt onto the transmission pulley. Release the tension pulley.

Step 7

Screw the cover back over the transmission pulley. Tip the mower back flat on the ground. Put the sparkplug cap back on the sparkplug.