2 Pieces 694394 Carburetor Primer Bulb for B&S 4178 494408 5084 Lawn Mowers Parts

What It Is

This is a two-pack of aftermarket carburetor primer bulbs (model 694394) designed to replace the OEM bulb on Briggs & Stratton engines. It’s used on walk-behind lawn mowers, pressure washers, and other small engines with a primer bulb system—pushing it forces fuel into the carburetor for easier cold starts.

Fitment & Compatibility

Check these before buying:

• OEM cross-references: Replaces B&S part numbers 694394, 4178, 494408, and 5084. Also fits many Toro, Craftsman, and MTD mowers with B&S engines.
• Measure the bulb: New bulb diameter is roughly 0.75 inches; ensure your mower’s primer bulb recess is the same size. The stem length is about 0.5 inches—measure your old bulb stem to confirm.
• Engine series: Works with most B&S single-cylinder engines (e.g., 450e, 500e, 550e, 625e, 725exi). Not for Intek or V-twin models with different primer systems.
• Deck size irrelevant: Fitment is engine-specific, not deck size. Verify your engine model number (stamped on valve cover or shroud).

Key Things to Know

• Quality: Aftermarket rubber is slightly stiffer than OEM—may take a few extra pumps to prime. Most users report it works fine, but some note it cracks faster in extreme cold.
• Installation: Easy—pop off old bulb, clean the carburetor housing (debris causes leaks), push new one in until it seats. No tools needed.
• Common gotcha: If the mower still won’t prime after replacement, check the fuel line or carburetor gasket for cracks. The bulb itself is rarely the only issue.
• Two-pack value: You get a spare for roughly the price of one OEM bulb—useful if you mow frequently or store the mower in direct sun (UV degrades rubber).

Should You Buy It

If you have a common B&S engine (450e–725exi) and your primer bulb is cracked, collapsed, or missing, this is a solid, cheap fix. Avoid it if you’re looking for OEM-grade durability or have an unusual engine series—stick with the genuine B&S bulb for those.