594281 Lawn Mower Carburetor Primer Bulb for Briggs & Stratton 300E 450E 500E 08P502 09P6 Series

What It Is

This is an aftermarket replacement primer bulb (part number 594281) designed to fit specific Briggs & Stratton 300E, 450E, 500E, and 08P502/09P6 series engines. It’s used to manually pump fuel into the carburetor before starting, common on walk-behind mowers, pressure washers, and small generators.

Fitment & Compatibility

Before buying, confirm your engine’s model number (stamped on the valve cover or blower housing). This bulb fits Briggs & Stratton engines with the following series: 300E, 450E, 500E, 08P502, and 09P6. It replaces OEM part 594281 and also works for some 4900, 5900, and 6900 series. Measure the bulb’s stem diameter (typically 0.25 inches) and the mounting hole on your carburetor—if the bulb’s stem is too thick or too thin, it won’t seal. This is an aftermarket part, not OEM, so fitment may vary slightly on older or non-Briggs engines. Check that your carburetor uses a push-in style primer bulb (not a screw-on type).

Key Things to Know

• Quality: Aftermarket bulbs can be less durable than OEM—some users report cracking after a few months. Inspect the rubber for thin spots before installation.
• Installation: Easy—just push the stem into the carburetor’s primer hole. No tools required. Ensure the bulb seats fully and doesn’t leak air when pressed.
• Common gotcha: If the bulb feels loose or falls out, the carburetor’s mounting hole may be worn. A dab of silicone grease can help seal it, but replacement of the carburetor might be needed if the hole is enlarged.
• Check for debris: A clogged fuel line or carburetor jet can cause the bulb to collapse or not prime—clean the system first if the bulb is new but still doesn’t work.

Should You Buy It

This is a good budget fix if your current primer bulb is cracked, missing, or not sealing. It’s ideal for DIYers with a common Briggs & Stratton engine who need a quick, cheap repair. However, if you have an older engine or a carburetor with a damaged mounting hole, save your time and replace the entire carburetor instead. For heavy-use mowers, consider OEM for longer life.