How to Adjust a Snowblower Valve Lash

 

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This step-by-step repair guide gives instructions for adjusting the valve lash on a snowblower engine. The valve lash is the space between the top of the valve stem and the rocker arm. Incorrect valve lash prevents the valve from opening or closing properly, making the engine hard to start, sluggish and underpowered. Incorrect valve lash also can cause valve failure. Check valve lash after the first 25 hours of use and then every 100 hours. Adjust valve lash using the steps in this repair guide.

Use this basic procedure to adjust the valve lash on Craftsman, MTD, Troybilt, Husqvarna, Toro, Murray, Ariens and Yard-Man snowblowers.

Repair difficulty:
     
Time required:

Less than 30 min.

Parts Required

  • Rocker cover gasket

For manuals, repair guides, and specific part recommendations, enter your model number.

Tools Required

  • Wrench set
  • Work gloves
  • 12-in wooden dowel
  • Feeler gauge
  • Socket set with ratchet
  • Ratchet extension
  • 13/16" spark plug socket
  • Needle-nose pliers
  • Shop towel
  • Torque wrench

Before you begin

Allow the engine to cool. Wear work gloves to protect your hands.

Instructions

 Warning: Undertaking repairs or maintenance to appliances or power equipment can be hazardous. Should you choose to undertake repairs or maintenance, you are assuming the risk of injury to your person or property. In an effort to reduce the risk, use the proper tools and safety equipment noted in the applicable guide and follow all instructions. Do not proceed until you are confident that you understand all of the steps and are capable of completing the repair. Some repairs or maintenance, however, should only be performed by a qualified technician.

How to Adjust the Valve Lash

Step 1: Remove the spark plug

Disconnect the spark plug wire.

Use a deep socket and a ratchet to remove the spark plug from the cylinder.

Step 2: Remove the rocker cover

Place a shop towel under the rocker cover to catch oil.

Remove the 4 rocker arm cover screws using a socket.

Pull the rocker cover off the engine.

Squeeze the breather hose clamp and pull the hose off the rocker cover.

Remove the rocker cover.

Step 3: Position the piston at top dead center

Insert a 12-inch wooden dowel into the spark plug hole and rest it on top of the piston.

Slowly pull the starter rope to cycle both valves and reach the compression stroke. You’ll know you’ve reached the compression stroke when both valves are closed and the piston is moving up.

Continue to pull the starter rope until the dowel reaches its full extension out of the spark plug hole.

Both valves will be closed and both rocker arms will be slightly loose when the piston is at top dead center on the compression stroke.

Step 4: Measure the valve lash clearance

Insert the feeler gauge between the intake rocker arm and valve stem to measure valve lash clearance.

The intake valve is on the carburetor side of the engine.

Intake valve lash clearance should be .003-inch to .005-inch on this engine.

Try to insert a feeler gauge leaf into the gap between the rocker arm and the valve stem until you find the leaf that slips in with slight resistance.

Note the measurement on the leaf that fits the intake valve lash clearance.

Repeat the measurement process for the exhaust valve on the muffler side of the engine.

The exhaust valve lash clearance should be .005-inch to .007-inch.

Note the measurement on the leaf that fits the exhaust valve lash clearance.

Step 5: Adjust the valve lash clearance

Loosen the jam nut while holding the fulcrum nut stationary with a wrench.

Turn the rocker arm fulcrum nut clockwise to decrease the interior valve lash clearance or counterclockwise to increase it.

Once you reach the proper valve lash clearance, hold the rocker arm fulcrum nut stationary with a wrench and tighten the jam nut to 80- to 106- inch-pounds using a torque wrench.

Recheck the valve lash clearance after tightening the jam nut.

Adjust the valve lash clearance on the exhaust valve if needed.

Step 6: Recheck the valve lash clearance

Rotate the engine through several compression cycles.

Return the piston to top dead center of the compression stroke.

Recheck the valve lash clearance and adjust the valves again if necessary.

Step 7: Reinstall the rocker cover

Clean up oil around the rocker arms.

Examine the rocker cover gasket and replace it if damaged. Clean any old gasket residue off the cylinder head and rocker cover before installing a new gasket.

With the gasket pressed into the rocker cover, reinstall the rocker cover on the engine.

Tighten the rocker cover screws to 62- to 80-inch-pounds using a torque wrench.

Reattach the breather hose and secure it using the hose clamp.

 Warning: Over tightening the rocker cover screws could cause an oil leak between the rocker cover and cylinder head.

Step 8: Reinstall the spark plug

Thread the spark plug into the cylinder and tighten it using the deep socket and ratchet.

Reconnect the spark plug wire.