HUSQVARNA YTH18542 BELT KEEPS COMING OFF General Troubleshooting

Mower Deck Drive Belt

The most common cause for a belt jumping off is elongation. Over time, the internal cords stretch, exceeding the take-up capacity of the idler arm. Once the belt is slack, centrifugal force during engagement causes it to whip and hop over the pulley flanges.

SKU: 532197253

Deck Idler Pulley

If the internal bearing of the idler pulley becomes 'notchy' or worn, the pulley will tilt under the high tension of the belt. This misalignment creates a 'steering' effect that actively pushes the belt out of the groove, especially when the mower deck is engaged in thick grass.

SKU: 532196106

Deck Tensioner Spring

This extension spring provides the lateral force for the idler arm to keep the belt taut. After repeated heat cycles and stress, the spring undergoes plastic deformation (stretching), which reduces the tensioning force and allows the belt to become loose enough to jump the pulleys.