UDC Parts 539110311 Idler Pulley Replacement for Husqvarna Craftsman and Poulan Mower 14259 607163 MZ6125 RZ3016 RZ4219 RZ4619

What It Is

This is a 4-inch diameter, steel idler pulley designed to guide and tension the mower deck belt on select Husqvarna, Craftsman, and Poulan zero-turn and lawn tractors. It replaces a worn or seized pulley that causes belt slippage, squealing, or poor cutting performance.

Fitment & Compatibility

Before buying, verify three things:

• OEM cross-reference: This pulley replaces Husqvarna part numbers 539110311, 14259, and 607163. It also fits Craftsman and Poulan models using those OEM numbers.
• Model list: Confirmed to fit Husqvarna MZ6125, RZ3016, RZ4219, RZ4619; Craftsman ZTS 6000, 7000; Poulan Pro PPB460, PPB500, and similar zero-turn mowers with a 4-inch pulley. Not for push mowers or older belt-driven walk-behinds.
• Measurements: Outer diameter is 4 inches, inner bearing bore is 5/8 inch. The pulley uses a 6202-2RS sealed bearing. Measure your old pulley’s diameter and bore—if they match, it’s compatible. Also check deck belt routing: this is a smooth, flat idler, not a grooved tensioner.

Pro tip: Search your mower’s model number (e.g., “917.289620”) online with “idler pulley 4 inch” to confirm. If your deck uses a 3.5-inch or 4.5-inch pulley, this won’t fit.

Key Things to Know

• Quality: All-steel construction with a sealed bearing—holds up better than plastic idlers common on budget replacements. The bearing is pre-greased and should last 2–3 seasons under normal use.
• Installation: Easy, 10-minute job. You’ll need a socket set (usually 1/2-inch or 5/8-inch wrench for the bolt). No special tools. The pulley spins freely by hand—if it feels rough or gritty, return it.
• Common gotcha: The bolt hole is 5/16-inch, so use the original bolt or a grade 5 bolt of the same size. Over-tightening can crush the bearing—hand-tighten plus 1/4 turn is enough.
• Wear indicator: If your belt is frayed or glazed, replace it at the same time. A new pulley on a worn belt will wear out faster.

Should You Buy It

Yes, if your mower uses a 4-inch, 5/8-inch bore idler pulley from the Husqvarna/Craftsman/Poulan zero-turn family. It’s a direct, no-guess replacement at a fair price, with strong reviews confirming fit and durability. Avoid if your pulley diameter or bore differs, or if you need a grooved tensioner pulley.