503936601 Primer Bulbs Air Purge Pump for 188-512 Husqvarna Stihl Craftsman MTD 791-683974B Ryobi 683974B Oregon 49-088 Poulan 188-512 Snap in Primer Bulb for 2-Cycle Small Engine

What It Is

This is a snap-in primer bulb (air purge pump) designed for 2-cycle small engines on chainsaws, trimmers, leaf blowers, and other handheld outdoor power equipment. It replaces a worn or cracked bulb that won’t hold prime, making cold starts easier.

Fitment & Compatibility

Before buying, check that your existing bulb is a snap-in (not screw-in) type. Measure the bulb’s outer diameter (typically 0.5–0.6 inches) and the mounting hole size. This specific part (503936601) cross-references with many brands: Husqvarna 188-512, Stihl 0000 350 2400, Craftsman 791-683974B, MTD 683-974B, Ryobi, Oregon 49-088, and Poulan 188-512. It does not fit all 2-cycle engines—verify your model’s OEM part number against the list above. No deck size to check; this is for handheld equipment only.

Key Things to Know

• Quality: Durable rubber compound resists cracking from fuel and UV exposure, but aftermarket bulbs can vary slightly in stiffness compared to OEM.
• Installation: Easy—pop out the old bulb with a flat screwdriver, press the new one in until it snaps. No tools required. Takes under 2 minutes.
• Common gotcha: If the bulb doesn’t snap in firmly, the mounting grommet or housing may be worn. Replace the grommet if needed for a tight seal.
• Warranty: EGO offers a 30-day return window; check seller return policy for defective units.

Should You Buy It

If your 2-cycle engine’s primer bulb is hard, cracked, or won’t hold prime, this is a reliable, low-cost fix. It’s a direct replacement for dozens of common models and fits most snap-in housings. Avoid if your machine uses a screw-in bulb or if the housing is damaged.