594593 796109 Carburetor For Brigg & Stratton 591731 590400 794572 796078 31H777 31G777 31H707 31H777 31L777 31M777 31M877 14.5/15.5/16.5/18/21 HP Engines Carb

What It Is

This is an aftermarket carburetor designed to replace OEM part numbers 591731, 590400, 794572, and 796078 on Briggs & Stratton single-cylinder engines. It fits engines in the 14.5 to 21 HP range, commonly found on riding mowers and zero-turn mowers from brands like Craftsman, John Deere, Troy-Bilt, and Husqvarna.

Fitment & Compatibility

Before buying, confirm your engine’s model number (e.g., 31H777, 31G777, 31M777, 31M877). This carburetor is not universal—it only matches the specific engine families listed. Check your engine’s model number on the valve cover or blower housing, not the mower deck size. Measure the mounting bolt spacing (center-to-center: ~2.5 inches) and the fuel inlet nipple diameter (~1/4 inch) to verify physical fit. If your engine uses a different fuel line size or a primer bulb, this carburetor may not include those components.

Key Things to Know

• Quality varies: At this price point, expect a functional but not OEM-grade part. Some units may need minor adjustments to the float height or idle mixture screw.
• Installation is moderate: You’ll need to remove the air filter housing, fuel line, and throttle/governor linkage. Label linkage positions before disassembly to avoid confusion.
• Common issue: The included gaskets may be thin or misaligned. Use the original gaskets if possible, or add a thin layer of fuel-resistant sealant.
• No primer bulb or fuel filter included: You may need to reuse your old ones or buy separately.

Should You Buy It

This carburetor is a good budget option if your OEM part is clogged or damaged beyond cleaning and you’re comfortable with basic small-engine repair. It’s not for someone who expects drop-in perfection—plan on spending 20–30 minutes tuning and verifying fit. For a critical machine or if you want zero hassle, stick with an OEM replacement.