Hoypeyfiy Primer Bulb Replacement for B&S Lawn Mower 694395, 4180,5085, 5085H, 5085K (Pack of 4)

What It Is

This is a set of four aftermarket primer bulbs designed to replace the deteriorated or cracked rubber bulb on Briggs & Stratton lawn mower carburetors. The primer bulb sits on the carburetor’s fuel bowl and is used to manually pump fuel into the carburetor before starting a cold engine.

Fitment & Compatibility

Before purchasing, confirm your engine’s carburetor uses a push-in style primer bulb (not a screw-in or integrated cap type). These bulbs replace B&S OEM part numbers 694395, 4180, 5085, 5085H, and 5085K – common on many B&S single-cylinder engines from the 1990s through 2010s.

What to check:

• Carburetor model: Look for a small round rubber bulb on top of the carburetor fuel bowl, about ½ inch in diameter.
• Physical measurements: Bulb diameter is ~0.5 inches; stem length ~0.3 inches. Measure your old bulb’s stem diameter and depth to ensure it seats fully.
• Deck size irrelevant: This part fits the engine carburetor, not the deck – engine model number (e.g., 12H802, 10T502) is what matters.
• Aftermarket note: These are not OEM B&S parts; they may be slightly softer or stiffer than original rubber. They work on most B&S carburetors that accept a push-in bulb, but may not fit aftermarket replacement carburetors with different bulb recesses.

Key Things to Know

• Installation difficulty: Easy – pull out the old bulb (may need pliers if stuck), push the new one firmly into the hole until it seats flush. No tools required beyond maybe a pick or small flathead.
• Common gotcha: The bulb can pop out if the stem is too short or the hole is worn. Apply a tiny dab of fuel-resistant RTV or super glue around the stem if it feels loose.
• Quality: Users report these bulbs work well for the price, but a few mention slight fitment looseness on some carburetors. The pack of 4 gives you spares if one fails or is too loose.
• Not for all B&S engines: Some newer B&S engines use a primer bulb integrated into the air filter cover or a different carburetor design – verify your carburetor has a separate push-in bulb before buying.

Should You Buy It

If you have a Briggs & Stratton lawn mower with a push-in primer bulb that’s cracked, hardened, or missing, this cheap 4-pack is a solid fix. It’s ideal for DIYers who want a quick, low-cost repair and don’t need OEM branding. Avoid it if you need a perfect factory fit or have a carburetor with a different bulb retention system (like a screw-on cap).