How to Repair a Lawnmower Chain

Park the lawn mower on a flat surface so that it sits level. Turn off the engine and lower the mower deck via the mower's deck lift lever.

Bend down to look under the mower's deck. The pulley holding the mower's drive chain can be seen near the center of the deck, and just beside the chain is the spring loaded idler. The idler appears as a distinctive, circular piece with a bolt near the top of its metal plate. Loosen this bolt with counterclockwise turns from a socket wrench.

Insert a breaker bar into the square hole on the idler plate, then crank the bar clockwise to tighten the chain until you feel resistance. Immediately stop cranking once resistance is felt, otherwise you risk damaging the chain.

Use your socket wrench to tighten the mower's idler plate bolt back into position.

Pull the deck lift lever up to raise the mower deck.