Lawn Mower Valve Adjustment Symptoms And The Solutions

You need to keep a sharp eye on some common lawn mower valve adjustment symptoms. Because poor valve adjustment may result in a damaged lawnmower.

To be precise, the precise gap between the rocker and the valve head needs to be checked which is also known as valve lash.

In this guide, you will find the complete guide on noticing such symptoms, their impacts on your mower, and basic maintenance tips to deal with them. Keep reading!

Common Symptoms of Lawn Mower Valve Adjustment

lawn mower valve adjustment symptoms

  • Suddenly making an excessive tapping noise.
  • Hard to pull the starting cord.
  • Huge fuel consumption with rough running.
  • Sudden power loss and no start at all.
  • No compression.
  • Oil Leaks.

Later in this article, I will mention some consequences of bad valve adjustment and some highly effective tips to fix your mower. But it’s important to identify the above-mentioned signs of such adjustments as soon as possible.

Irrespective of brands and models, those signs are common. And just to let you know, some lawnmower brands should be avoided in the first place to avoid such problems.

So, each one of you should take action upon noticing such signs. But first, let’s talk about these signs in detail:

  1. Tapping Noise

An increase in the valve gap will result in increased tapping noise. It’s not a surefire but it’s definitely a good sign and hopefully, you may notice it before your neighbor does.

You should not ignore such tapping noise because it indicates the exhaust valve & the inlet is no longer supporting the engine to perform smoothly. Before the engine becomes off-balance pretty soon, you should fix the problem ASAP.

  1. Sudden Power Loss

Such behavior of your mower also indicates increased/decreased tappets that will result in decreased efficiency and power of the mower.

Not only it’s just harmful to your mower, it will consume more fuel without providing any extra performance. To keep it running for a long time and to have increased performance, you need to fix that.

  1. Hard Starting

Another common sign of valve gap (not aligned properly) is the hard starting of the mower. It simply indicates there is an increased valve gap that is affecting the whole mechanism of the mower valve movement.

Excessive valve lash may not be the only reason for hard starting but you should check the issue once in every season.

And the valve train timing will be out when the valve clearance is out of spec which in turn will result in hard starting.

Without fixing the problem, if you continue to hard start, it will harm the head gasket and you may notice oil leaking problem too.

  1. Lack or No Compression

A stuck valve results in a lack of compression and you can provide such compression to the spring easily. You don’t need a complex lawn mower valve adjustment tool for that.  A simple screwdriver is enough!

But for that, you should run a compression test every now and then to check the engine life.

It’s important to have enough compression on the spring because due to the damaged, stuck, or misaligned valve, the mower will have a starting issue.

  1. Pulling the Cord Becomes Hard

Almost every lawnmower has a compression release mechanism. To release the cylinder pressure, it opens the valve a little early. Under normal circumstances, that’s the reason you don’t need much power pulling the cord.

But it becomes hard due to the excessive valve lash.

One of the most common riding lawn mower valve adjustment symptoms is the harder case of pulling the starting cord.

The reason the cord becomes too hard to pull is due to the increased valve gap and excessive cylinder pressure.

Again, let me be very clear about it. The excessive valve lash is NOT the only reason why the cord becomes too hard to pull like faulty flywheel brake and key.

Some other reasons like the bent crankshaft, a faulty carburetor needle, blade obstruction from dry grass & broken branches may lead to the same problem.

Importance of Valve Adjustment of Any Lawn Mower

The reason why you should keep the valve adjustment smooth and functioning have many answers.

But in general, the overall performance of your mower largely depends on the steering alignment adjustments and exhaust valve maintenance.

Here are some of their importance and why you need to fix any problems related to it:

  • Ensuring the right opening and closing times of the valves is important. When your mower has the precise valve adjustment, it is perfectly ensured!
  • You get improved performance and engine mileage.
  • It provides much-needed space for thermal expansion.
  • Proper valve adjustment also results in lower fuel consumption.

The Solution

Before you start doing it yourself, I need to remind you something. The valve clearance differs from model to model. There are plenty of reasons why the lawn mower won’t start. So, read the manual first and learn the exact and ideal gap.

The lawn mower valve adjustment cost is high if done by a professional which you should pay if you don’t know what you are doing. It may make the situation worse!

But if you are cool with tools and engines and if you have the right tool and guide, it can be a fun DIY! Watch the very short but highly-effective instructional video to make yourself comfortable first.

Timely fixing the valve gap will prolong the life of your mower. Follow the steps to fix the valve adjustment problem:

  1. Without removing the pushrods, keep the engine rotating and the blades turning. That way you can keep the intake valves compressed and open.
  2. With the suitable lawn mower valve adjustment tool, remove the valve covering bolts & spark plug wire.
  3. Turn the blades to rotate the engine clockwise.
  4. To unload the valve springs, turn the object into the cylinder.
  5. Before you increase/decrease the valve gap, find the exhaust valve located at the muffler. Then you will find the rocker arm fixed right above the exhaust valve.
  6. Use a screwdriver to increase/decrease the gap between the valve and the setscrew. Get a feeler gauge to test the gap after you tighten the jam nut.
  7. Once you get the right valve adjustments, tighten the nut, and keep a record for future adjustments.

Frequently Asked Questions (FAQ)

How does a Briggs compression release work?

Answer: Almost every mower’s overhead-valve engine has a compression release feature so that you don’t have to pull it hard to start the engine. To bleed off the excess compression, it opens the valve a little early.

How do I know if I need my valves adjusted?

Answer: If the engine is making any tapping or clicking sound, it’s a surefire sign. However, do not wait for the engine to cry and let you know. Inspect the valve lash at the regular interval recommended by the manufacturer.

What happens when valves are out of adjustment?

Answer: The engine will have a breathing problem because of too little or too much valve clearance. That will result in poor performance of your mower.

What are the symptoms of bad valves?

Answer: Higher level of oil consumption, hard pulling the starting cord, not starting, a higher level of smoke, oil leaks, and so on.

What should compression be on a Briggs and Stratton?

Answer: Around 100-140PS.


You can’t tell for sure whether the valves need readjustment or not without examining them. But the engine will show some signs to guess the problems.

So, look at the engines and carefully observe the lawn mower valve adjustment symptoms. And take action ASAP!

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