Description
If you’ve ever struggled to hand-crank one of those classic John Deere tractors on a cold morning, you know the value of a compression relief petcock. This simple but essential valve temporarily reduces compression in the cylinders, making those old two-cylinders much easier to start by hand. When your petcock gets worn or starts sticking, you’re back to wrestling with full compression—something that’s tough on your back and harder on the engine.
What You’re Getting
- Solid brass construction that handles years of heat cycling without cracking
- Smooth operation that opens and closes easily even when hot
- Proper sealing that holds compression when closed but vents cleanly when open
- Direct replacement that threads right into your existing cylinder head port
Built for Real Farm Work
This petcock fits the vintage John Deere workhorses that built farming in America—the A, AO, AOS, AR, B, BO, BR, D, G, and GP series tractors. Whether you’re starting up a Model A for parade duty or firing up a Model D for belt work, these tractors were engineered for reliability, and this petcock keeps that tradition alive.
Made to Last
Brass was chosen for these petcocks because it handles the constant heat and pressure changes that come with engine operation. Unlike cheaper materials that crack from thermal stress, brass maintains its strength and sealing properties through countless start cycles while resisting corrosion from moisture and combustion byproducts.
Good to Know
Installation is straightforward—thread out the old petcock and thread in the new one with a bit of pipe sealant. Open the petcock before cranking, then close it once the engine fires up. These old engines were designed to run with the petcock closed during operation, so don’t forget that last step.
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