683974 Primer Bulb for Ryobi 791-683974B, W-albro 188-512 188-512-1Y, Homelite Wt-23a Wyj-33 Wyj-86, MTD YM1500 Y780 Y765 Y725 Y700VP

What It Is

This is a replacement primer bulb for small engines on Ryobi, Homelite, MTD, and other trimmers, blowers, chainsaws, and mowers. It’s the rubber button you press to push fuel into the carburetor for easier cold starts.

Fitment & Compatibility

Before buying, check your machine’s model number and the carburetor part number. This bulb fits:

• Ryobi 791-683974B (OEM)
• Walbro 188-512, 188-512-1Y
• Homelite WT-23A, WYJ-33, WYJ-86
• MTD YM1500, Y780, Y765, Y725, Y700VP

Measure the bulb’s diameter (typically ~0.5–0.6 inches) and stem length. It’s a direct replacement for these specific carburetors; it won’t fit universal primer bulbs with different dimensions. If your carburetor isn’t listed, remove the old bulb and compare shape/size.

Key Things to Know

• Quality: OEM-equivalent; users report it’s durable and seals well. No known premature cracking or leaking.
• Installation: Easy—pop the old bulb out of its retainer, push the new one in. No tools required, but be careful not to tear the rubber.
• Gotcha: If your primer bulb is hard or cracked, it may have failed due to ethanol fuel. Consider using fuel stabilizer to extend the new bulb’s life.
• Gotcha: If the mower still won’t prime after replacement, check the fuel line and carburetor gasket for cracks, not just the bulb.

Should You Buy It

If your small engine’s primer bulb is stiff, cracked, or won’t hold prime, this is a cheap, reliable fix. It’s ideal for DIYers who want a quick, no-fuss replacement—just verify your carburetor model matches one listed above.