Stens 280-737 Flat Idler Compatible with/Replacement for Exmark Lazer Z mowers 109-8590, 116-9639 Black

What It Is

The Stens 280-737 is a flat idler pulley designed to maintain belt tension on the deck spindle drive system of Exmark Lazer Z mowers. It replaces worn or seized pulleys that cause belt slippage, noise, or poor cutting performance.

Fitment & Compatibility

• Direct replacement for: Exmark OEM part numbers 109-8590 and 116-9639.
• Fits these Exmark Lazer Z models: Lazer Z (all series), Lazer Z X-Series, Lazer Z HP, and Lazer Z S-Series with 48", 52", 60", or 72" decks.
• What to measure before buying: Outer diameter (approx. 5.0"), inner bearing bore (5/8"), and thickness (0.75"). Compare against your existing pulley.
• Note: Not compatible with Lazer Z CT or Lazer Z Advantage series—those use a different idler design.
• Aftermarket vs OEM: Stens is a quality aftermarket brand. It uses sealed ball bearings (not bushings) for longer life than some OEM pulleys.

Key Things to Know

• Quality: Stens 280-737 uses double-sealed bearings, which resist debris better than OEM single-seal versions.
• Installation: Easy—remove the old pulley bolt, swap pulleys, and torque to 25-35 ft-lbs. No special tools needed.
• Common gotcha: The flat idler is often confused with the spring-loaded tensioner pulley. This is a fixed, non-spring idler—verify you’re replacing the correct one.
• Check belt condition: If the idler is worn, the belt likely has glazing or cracks. Replace both at the same time for best results.

Should You Buy It

If you own a compatible Exmark Lazer Z and need a reliable, drop-in replacement for a worn OEM idler, this is a solid choice. It’s slightly cheaper than OEM, uses better bearings, and has strong user feedback. Skip it only if you need a spring-loaded tensioner or have a non-Lazer Z model.