Fuel Tank Gas Cap 799585 Replacement for B&S Mower 550E & 550EX Series, 625E, 675EX & 725EX Series & Professional Series 7.75-8.75 Engines, Replaces 799684

What It Is

This fuel tank gas cap (part 799585) is a direct replacement for Briggs & Stratton engines in the 550E, 550EX, 625E, 675EX, and 725EX series, plus Professional Series 7.75–8.75 engines. It seals the fuel tank to prevent leaks and debris ingress during mowing.

Fitment & Compatibility

• Exact match required: This cap fits only specific B&S engine families (listed above). It does not fit older or non-B&S engines.
• OEM cross-reference: Replaces B&S part 799684. Confirm your engine’s part number on the engine shroud or manual.
• Measurement check: Cap diameter is approximately 1.5 inches (38mm) – measure your tank opening before ordering.
• Deck size irrelevant: Fitment depends solely on engine model, not mower deck width.

Key Things to Know

• Quality variance: At $7.99, this is an aftermarket cap. Some users report looser fit than OEM – ensure it threads fully and seals tight.
• Installation is trivial: Unscrew old cap, screw on new one. No tools required.
• Common gotcha: If your old cap has a tethered retainer, this replacement may not include one – check description.
• Vent check: Some B&S caps have a built-in vent; if your mower runs poorly after replacement, verify this cap vents properly.

Should You Buy It

Buy this if you need a quick, low-cost fix for a lost or cracked gas cap on a compatible B&S engine and don’t mind a slightly looser fit than OEM. Skip it if you require a perfect OEM-grade seal or a tethered cap.