Briggs & Stratton 5101651SM Fuel Cap

What It Is

The Briggs & Stratton 5101651SM Fuel Cap is a replacement vented cap for Briggs & Stratton engines used on walk-behind mowers, riding mowers, and some generator/utility engines. It prevents fuel spillage while allowing proper air flow into the tank.

Fitment & Compatibility

• OEM part – This is a genuine Briggs & Stratton cap, not an aftermarket clone.
• Check your engine model – Fits most Briggs single-cylinder engines (e.g., 450, 500, 550, 575, 625, 675, 700, 725, 750, 775, 800 series) and some V-twin models.
• Physical check – Measure your fuel tank opening: this cap fits a standard 1.5-inch diameter neck with a bayonet-style twist lock. If your cap is a push-in or has a different thread pattern, this won’t work.
• Cross-reference – Also replaces older part numbers 591889, 698050, 698051, 792015, and 790441. Verify your engine’s model/type/code on the Briggs site or your manual.

Key Things to Know

• Venting is critical – If your mower runs rough or stalls after a few minutes, the old cap’s vent may be clogged. This new cap restores proper air intake.
• Easy install – No tools needed. Just twist off the old cap and twist on the new one. Takes 30 seconds.
• Quality note – Some users report the plastic feels slightly thinner than older OEM caps, but it seals well and vents correctly. Avoid over-tightening.
• Not universal – Will not fit Honda, Kawasaki, Kohler, or Tecumseh engines unless they use the same bayonet pattern. Always confirm with your engine model.

Should You Buy It

If your Briggs engine is stalling, flooding, or leaking fuel from the cap, this OEM replacement is a reliable, low-cost fix. It’s a direct swap for most popular single-cylinder and small V-twin Briggs engines. Skip it if your engine uses a push-in or threaded cap – measure first.