E-YooHoo Set of 2, 694394 Replacement Lawn Mowers carburetor Primer Bulb for fits Briggs & Stratton 4178 494408 5084

What It Is

This is a set of two replacement primer bulbs for small engines, specifically designed to fit many Briggs & Stratton lawn mowers. The bulb sits on or near the carburetor and is pushed to force fuel into the carburetor bowl for easier starting.

Fitment & Compatibility

• OEM cross-references: This bulb replaces Briggs & Stratton part numbers 694394, 4178, 494408, and 5084. It is an aftermarket part, not OEM.
• What to measure: The bulb’s outer diameter is approximately 1 inch (25mm), and the stem diameter is about 0.25 inches (6.3mm). Compare these to your existing bulb before buying.
• Mower fitment: Works on many Briggs & Stratton engines from the 1980s through early 2000s, including 3.5–5 HP models. Not universal—check your engine’s model number (stamped on the valve cover or blower housing) against the cross-references.
• Deck size: Not relevant—this part fits the engine, not the deck.

Key Things to Know

• Easy install: No tools required—just pull off the old bulb and push the new one into the carburetor primer port. Takes under 2 minutes.
• Quality note: These are aftermarket rubber bulbs. They may feel slightly stiffer than OEM, but most users report they work fine. A few note they can crack after a season in direct sun or extreme cold.
• Common gotcha: If your mower still won’t start after replacing the bulb, the issue is likely a dirty carburetor or clogged fuel line—not the bulb itself.
• Two-pack value: You get two bulbs for the price of one OEM. Keep the spare in your shed for quick replacement next season.

Should You Buy It

If your Briggs & Stratton mower has a cracked or missing primer bulb and you want a cheap, easy fix, this is a solid choice. It’s not OEM, but it works for most users and costs a fraction of the original part. Best for people who want a quick repair without hunting down a dealer.