Fuel Tank Cap 779306 Compatible for Hustler Super Z Mower 3.5" Inside Diameter Cub Cadet 751-3124B 751-3124D Husqvarna 539106188 Toro 88-3980 951-3124B

What It Is

This is a replacement fuel tank cap with a 3.5-inch inside diameter, designed for zero-turn mowers like the Hustler Super Z, and compatible with several OEM part numbers. It seals the fuel tank to prevent leaks and debris entry while allowing proper venting during operation.

Fitment & Compatibility

• Measure first: The critical spec is the 3.5-inch inside diameter. Measure your current cap’s inner opening (not the outer rim) to confirm fit. Mismatched diameters will not seal.
• Cross-reference OEM numbers: This cap replaces Hustler 779306, Cub Cadet 751-3124B/751-3124D, Husqvarna 539106188, and Toro 88-3980/951-3124B. If your mower uses any of these, it’s a direct swap.
• Brand coverage: Primarily for Hustler Super Z, but also fits many Cub Cadet, Husqvarna, and Toro zero-turn models with the same tank opening. Check your mower’s manual or existing cap part number before buying.
• Aftermarket note: This is an aftermarket (non-OEM) cap, but matches OEM specs. If your mower is under warranty, OEM may be required to avoid voiding coverage.

Key Things to Know

• Quality is solid: Made of durable plastic with a rubber gasket. The 5.0/5 rating (9 reviews) suggests good sealing and no premature cracking or venting issues.
• Installation is trivial: Unscrew the old cap, screw on the new one. No tools needed. Takes under 30 seconds.
• Venting check: Ensure the cap has a vent hole (most do). A non-vented cap can cause vacuum lock, stalling the engine. If your old cap had a vent, this one should too—but verify after fitting.
• Gasket condition: The rubber gasket can compress over time. If the cap feels loose after tightening, the gasket may need replacing, but this cap includes a new one.

Should You Buy It

Buy this if you need a direct replacement for a Hustler Super Z or compatible zero-turn mower with a 3.5-inch fuel tank opening and want a budget-friendly, well-reviewed aftermarket option. Avoid if your mower uses a different diameter or you require OEM for warranty purposes.