Testing and replacing the flywheel key on a leaf blower

Got a leaf blower that’s acting up just when those autumn leaves are piling up? The culprit could be a busted flywheel key. By figuring out how to spot and swap a sheared flywheel key, you can get your blower back in business without too much fuss.

The information in this article may not apply to your specific appliance model. We recommend consulting your manufacturer’s documentation or contact us with any questions.

What is the flywheel key?

The flywheel key might be small, but it plays a big role in making sure your leaf blower’s engine timing is just right. It keeps the flywheel and crankshaft in sync, so your engine starts up and runs smoothly. If it’s snapped or damaged, the timing gets thrown off, leading to starting problems or the engine running rough.

Why do flywheel keys get damaged?

There are a few reasons why this tiny piece might break:

• Engine backfires: Sudden backfires or the engine stopping abruptly can shear the flywheel key. This can happen if the blower’s not started properly or if there are some internal problems.
• Bad assembly: If the engine parts aren’t put together right, it can put too much stress on the flywheel key, causing problems over time.
• Using it wrong: Running the leaf blower in ways the manufacturer never intended can wear down internal parts—including the flywheel key.

Signs your flywheel key is bad

• Engine won’t start: The most common sign is the engine not turning on, even though you have fuel and a good spark plug.
• Runs rough: If it does start, the engine might sputter or stall after a bit.

What you’ll need

Before diving in, grab these tools to make things smoother:

• Flywheel puller
• Socket wrenches and ratchet set
• Torx bits (if needed)
• Feeler gauge or a flat file
• Safety gloves and goggles

Safety first!

Your safety’s no joke. Take these precautions:

• If working indoors, make sure there is adequate ventilation to prevent the buildup of exhaust fumes. Carbon monoxide poisoning can be a serious risk.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Never attempt to service or repair while it is running or when the engine is still warm. Wait for all moving parts to come to a complete stop.
• Exercise extreme caution when working near blades, augers, or any other moving parts. Keep your hands, fingers, and clothing clear of these areas at all times.
• If the appliance has recently been used, give it plenty of time for any hot parts to cool down before working on it. 
• Empty the gas tank before beginning any work. Refill using fresh fuel. 
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• When not in use, store the machine in a safe and dry location.

Step-by-step: check and replace the flywheel key

Get to the flywheel

1. Remove the shroud: Use the right screwdriver or wrench to take off the screws holding the engine shroud. Set it aside.
2. Take off other parts: Depending on your model, you might need to remove the recoil starter or air filter housing. Check your model’s manual for details.

Check out the flywheel and key

1. Look for damage: Inspect the flywheel for cracks, broken fins, or any other issues.
2. Examine the keyway: Check the groove where the flywheel key sits. If there are tiny burrs, you can smooth them out with a file.
3. Assess the flywheel key: It’s usually a small metal piece. If it’s broken or bent, it’s time for a new one.

Pull off the flywheel

1. Use a flywheel puller: Attach it following the manufacturer’s instructions. It’ll help you remove the flywheel without causing any harm.

Swap in the new flywheel key

1. Take out the old key: Gently remove it from the crankshaft keyway.
2. Pop in the new key: Place the new flywheel key into the keyway. It should fit snugly without wobbling.
3. Line up the flywheel: Put the flywheel back on the crankshaft, aligning it with the new key.

Put everything back together

1. Tighten the flywheel nut: Secure the flywheel by tightening the nut to the torque specified by the manufacturer.
2. Reattach parts: Put back any parts you took off earlier, like the recoil starter, air filter housing, and shroud.
3. Reconnect the spark plug: Hook the spark plug lead back up.

Fire up the leaf blower

1. Try starting the engine: With everything back in place, see if your leaf blower starts up.
2. Watch for issues: If it starts and runs smoothly, you’re golden! If not, you might want to check out more repair tips.

Extra pointers

• Stick with OEM parts: Always use a flywheel key made for your specific engine model to keep things running right.
• Keep up with maintenance: Regularly check your leaf blower for wear and do routine maintenance to prevent future problems.
• Read the manual: Your blower’s manual has specific advice that’s helpful during repairs.

More information

Thanks for reading! If you need replacement parts, grab your model number and head to AppliancePartsPros.com. We offer over two million parts and most orders arrive in two business days. If you need help finding the right part or placing an order, you can contact our team at 1 (877) 477-7278.

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