Turn off the motor and allow the mower to cool completely. Disconnect the spark plug wire to prevent the mower from accidentally starting while you're adjusting the drive chain.
Take out the screws securing the drive chain cover; the type and number of screws varies by brand and model. Remove the drive chain cover to reveal the chain and sprocket assembly. Loosen, but do not remove, the bolts on the front of the assembly.
Find the adjustment nut directly behind the sprocket assembly. Turn the adjustment nut clockwise to tighten the chain tension or counterclockwise to loosen it. Adjust the mower chain so that the slack side has no more than a half-inch of give at the midpoint.
Tighten the loosened sprocket assembly mounting bolts and replace the removed drive chain cover.
Things You Will Need
- Adjustable wrench
- Remove the drive chain from the assembly if your mower model doesn't have an adjustment nut. Find the chain's master link and open it with a small, flat-head screwdriver. Remove the master link. Remove or add links as needed to adjust the chain tension.