How to Adjust Valve Clearances

The beauty of Stand Commercial Mowers is their ability to allow you to mow large lawns in a relatively short time. If you own a stand-on mower or probably have a lawn care business that involves using these powerful commercial mowers, you probably would like to get the best out of your equipment and at the same time keep it running a long time. What can you do to accomplish this?

There are some periodic maintenance procedures that are a must if you are to maximize your mower’s engine performance as well as extend its lifespan. Today we will share one of those maintenance procedures; adjusting the valve clearances of your stand-on commercial mower.

What you will need

  • Thickness gauge set.
  • A 6-inch adjustable wrench.
  • A torque wrench.
  • Absorbent cleaning cloths.
  • Rubber gloves.
  • An Allen screwdriver.
  • A flat screwdriver.


Important Things to Note Before You Start

  • Ensure that your stand-on mower and work area are clean.
  • These tips might be applicable to stand mowers that use Kawasaki FX, FS, and FR engine series.
  • Basic maintenance knowledge like knowing mower engine parts and prior safety procedures might be required.
  • It might require going through these procedures thoroughly before tampering with your equipment.
  • Valve clearances must be checked when the engine is cold ( at room temperature.)

A Step-by-Step Guide

Figure #1

Figure #1

Figure #2

  • Standing in front of your stand mower while facing it, you will see one valve cover on your right and the other on your left, in this job card, we will start with the one on the right.
  • Place an absorbent cleaning cloth directly below the valve cover (rocker cover) on your right to hold any oil that will drip during the process.
  • Remove the valve cover by untying its supporting bolts.
  • Clean any existing oil in the valves area with a clean absorbent cloth.
  • To get the right position where you can easily adjust both the inlet and exhaust valve clearances (Top Dead Centre. TDC), open the engine’s top cover and expose its flywheel.
  • Turn the flywheel in a clockwise direction as seen in Figure #1 until the right foot of the magnet on the flywheel is directly opposite the left arm of the ignition coil on your right.
  • Swipe the thickness gauge set between the rocker arms and the valve stems.
  • At this point, there should be a clearance between both rocker arms and their valve stems respectively (inlet valve and exhaust valve stems.)
  • If there is no clearance between the two rocker arms and their respective valve stems, turn the flywheel again until it is in the same position as the one mentioned above.
  • If there is a clearance in both valves, use a thickness gauge set to see how wide they are. The recommended clearance range for both inlet and exhaust valves according to Kawasaki service manual of a 4-stroke, air cooled V-twin gasoline engine of series FX, FS, and FR ranges from 0.1m to 0.15mm ( 0.004 to 0.006 inch.) when the engine is cold.
  • If it is bigger or smaller than the recommended range, adjust the space to be within the recommended range.
  • To adjust, you might need someone to hold the thickness gauge set between the rocker arm and the valve stem.
  • Hold the rocker arm bolt with an adjustable wrench and loosen its locking nut with a torque wrench.
  • Keep turning the rocker arm bolt back and forth until the gauge tool gently touches the rocker arm and the valve stem.
  • The gauge tool should touch the rocker arm and the valve stem but also be easily swiped between the rocker arm and the valve stem without any hindrance.
  • Hold the rocker arm bolt in that position and tighten the locking nut to a specified torque (the specified torque is 11 NM, or 1.1 kgf.m or 87 in.lb.)
  • To adjust the second valve, repeat the same procedures mentioned above.
  • At this point, you have finished adjusting the valves on your right.
  • Put back the valve cover and tighten its supporting bolts.
  • To adjust the valves on your left, rotate the flywheel in a clockwise direction as seen in figure #2 until the right leg of its magnet is directly opposite the left arm of the ignition coil on your left.
  • Check the clearances by inserting a thickness gauge in between its valve stems and rocker arms ( inlet valve stem and exhaust valve stem.)
  • If the clearance is wider, adjust it to its recommended range using an adjustable wrench and a torque wrench.
  • Put back the valve cover.
  • At this point, you are done and your stand mower is ready for use.

Valve clearance adjustment can basically take you not more than an hour to have it done and you can do all this by yourself without necessarily hiring a mechanic. All you will need is a thickness gauge, a 6inch adjustable wrench, a torque wrench, cleaning cloths, rubber gloves, an Allen key, and a flat screwdriver and you will be ready to perform this task.

Benefits of Periodically Adjusting Valve Clearances

  • It helps in eliminating engine power loss and thus allow your equipment to perform at its expected horsepower.
  • Eliminating the knocking or pinging noise in your engine.
  • Maximizing its output and lifespan.
  • Avoiding possible damage of the entire cylinder head and other critical parts like push rods, valve stems, and more.

As your stand mower operates, the powerful vibration it delivers can easily cause bolts like the ones holding the rocker arms to loosen. Left unchecked, valve clearances will increase. That is the reason why it should be included among the list of things you should periodically do. So don’t delay, promptly adjust them and your stand-on mower will deliver its expected output.

Those are the steps you will need to successfully adjust the valve clearances of your equipment. Try them out the next time you maintain your stand mower and let us know how your DIY maintenance goes. In case of any question, suggestions, or clarification, feel free to comment below and we will be more than ready to help.


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