A self-propelled walking mower uses a drive belt or chain connected to a crankshaft on the engine for turning the front or rear wheels. This makes it easier to cut the grass, since you essentially need only to steer the mower, which pulls itself along. If the drive wheels are not turning enough on your mower, or rotate only intermittently, the drive belt or chain is the likely culprit. Try troubleshooting your mower before hauling it in to a repair shop.
Shut off the mower and pull the wire off the spark plug on the back of the engine for safety.
Unscrew and remove the protective housing over the drive belt or chain on the left or right side of your mower. The housing prevents objects from getting caught in the drive mechanism, potentially causing injury.
Pull on the drive belt or chain to confirm it is not broken. If your wheels are turning even a little, chances are the drive belt or chain is either loose or stretched.
Pull back on the tension pulley near the rear of the mower and tighten the bolt that secures it to the top of the mower housing with pliers.
Raise the drive handle on the handlebars of your mower or pull back on the drive lever, which is typically located on the left or right rod that attaches the handles to the mower housing. The handle or drive lever is connected to a cable that engages the tension pulley. The drive belt then tightens on the wheel axle to propel the mower. Hold the handle or lever in the drive position.
Pull on the drive belt or chain while the drive handle or lever is engaged. If the belt or chain holds tight to the pulley or gear on the drive wheels, you have corrected the problem. if the belt or chain pulls easily without engaging the wheels, the part should be replaced with a new belt or chain.
Loosen the tension pulley with pliers to remove the old belt or chain. Slip the new one over the crankshaft on the engine and the pulley or gear attached to the wheel axle, then tighten the tension pulley.
Place the protective housing over the drive mechanism and reattach with the screws.
Connect the sparkplug wire to the plug and crank the mower engine normally. Engage the drive handle or lever to propel the mower.