The primary driving force for a self propelled lawn mower is the belt. The belt saves mowers from pushing and pulling the lawn mower. A slow-moving or lawn mower that will not propel is an indication it is time to replace the belt. You can save money by DIY belt replacement, instead of taking the mower into a repair shop. For the majority of home owners, self propelled lawn mower belts should last around 2 years of regular mowing.
Review the owner's manual to obtain the measurements and type of drive belt used on the self propelled lawn mower. If none is provided, examine the lawn mower and locate the belt. Measure the width and approximate length of the belt with a tape measure. Write the measurement down. Write down the make and model of your lawn mower.
Go to your local lawn and garden store or home improvement store to purchase a new self propelled lawn mower belt. Use the information from step 1 to ensure purchasing the correct belt.
Set the lawn mower on a flat surface to make it easier to replace the belt. Put on a pair of work gloves. Locate and completely disconnect the spark plug.
Take the cover off the lawn mower. Re-locate the belt you are replacing. Near the belt, locate the belt guides. Loosen the bolts to the belt guides with an adjustable wrench (turning counter-clockwise).
Remove the worn-out belt. Place the new belt around the guides. Consult the owner's manual to ensure the proper routing of the new belt. Tighten the guides with an adjustable wrench (turning clockwise).
Replace the spark plug you removed during step 3. Turn on the self propelled lawn mower. Inspect to ensure the belt is moving properly. Turn off the lawn mower. Make any adjustments needed.