ATV Valve Adjustments, How Often? Quick Guide


Regular maintenance ensures that your ATV runs smoothly. What about valve adjustments? Valves allow fresh gas to flow into the combustion chamber and spent gas to exit. On average, valves require no more than periodic clearance, inspection, and occasional adjustments, but how often should you perform ATV valve adjustments?

ATV valve adjustments ought to take place every few months for most machines. However, if you own a high-performance ATV, you will want to check and adjust your valves after every 3-4 riding trips or during oil changes.

In this article, you’ll get a quick guide on how often to adjust your ATV valves. In addition, you will also learn the following:

  • What valve clearance means.
  • How valve adjustments work.
  • How valves slip out of adjustment.
  • What happens if you don’t make valve adjustments.
  • How slipped valves affect your ATV’s performance.

What Is Valve Clearance?

When a valve is closed, you need to have a gas-tight seal in the space between the valve seat and the valve face. To ensure the valve is well-seated, you need to have some valve clearance (lash) between the rocker arm and the valve stem. You can adjust the lash with a screw, shim, or with a hydraulic device.

As the engine heats up, the metals inside expand. This happens to the valve train components too. If the lash between the valve stem and its operating mechanisms is insufficient when the engine is at rest, it will be even more so when it gets hotter.

If the valve clearance is reduced too much, the following occurs:

  • The valve timing changes slightly, which might affect your ATV’s performance and emission outputs.
  • The valves restless in their seats, and exhaust valves don’t get enough time to give up their heat. This leads to detonation, pre-ignition, engine overheating, warped or burnt valves.

Again, if you remove the clearance, the valves get to sit a little further from the valve seat. This reduces the seat-to-valve-face contact area, giving combustion gases room to leak past.

By now, the engine might not start, and your valves are badly in need of attention. At this point, trying to start the engine could cause the exhaust valve to overheat or even burn. 

How To Tell if Your Valves Need Checking

Is there a way to tell whether your ATV valves need checking or adjusting without necessarily pulling the top to check the clearance? In other words, are there any particular signs that you need to look out for?

For starters, indeed, the most foolproof way to tell whether your valve clearances are in good shape (spec) is to pull the cover and measure them. Fortunately, there are other ways to tell. Out-of-adjustment valves usually make it easy for you to notice them because:

  • You’ll hear a distinct clatter from the valve area – this points to lose valves.
  • At times you might hear a click sound while idling.
  • You may notice a subtle loss of power (compression).
  • The bike could start overheating.
  • The intake valves tend to get tighter.
  • Tight valves might make it more challenging to start your ATV or lead to a poor idle.

In a nutshell, they might be noisy – if too loose- or the bike could lose compression or overheat – if too tight.

How ATV Valves Lose Clearance

ATV Valves can lose clearance (slip out of adjustment) due to several reasons, including:

  • Seat recession. This happens as the valve strikes into the valve seat, lessening operating clearance.
  • Loose valves: they occur as a result of normal wear between the components. As mentioned, loose valves are noisy, and since they hammer into other valve train components, they accelerate physical wear. Sometimes, a loose valve could cause a pushrod (in a pushrod engine) to fall off the rocker arm, destroying itself plus other pricy bits.
  • General wear and tear. With time, the valve face and the head tend to wear out. This causes the valve stem to rise higher and lessens your clearance. Again, with this wearing out, clearances usually tighten as the valve beds itself with the head.

Why It’s Important To Adjust Your Valves

What happens if you don’t adjust your valves? The reason for setting valve clearance is simple; metal expands when hot. Therefore, if the clearance gets too tight, the valve can’t fully sit in the head.

As mentioned previously, this situation can lead to compression loss or overheating. The latter can even lead to the valve’s destruction since the head helps to dissipate the heat from the valve. If the valve is unable to close fully, it loses the chance to transfer enough heat to the head.

And how does this affect your ATV?

If the valve is too tight, the ATV loses compression and performance while your gas mileage suffers. If it gets too loose, it becomes noisy and gets damaged by excessive clearance and metal bits slapping against each other.

Sometimes, if it gets too loose, the valve fails to open fully in a timely manner, and the engine fails to breathe optimally.

Finally, poorly adjusted valves can cause the entire valve train to wear out. Furthermore, if your valves have too much clearance, they can cause valve damage and failure, which can extend to the camshaft lobes and rocker arms. If you notice your valve train components failing, be sure to check the valve clearance.

When To Adjust Your ATV’s Valves

So, how often should you adjust your ATV Valves, or should you base this on standard maintenance intervals? Well, this depends on your machine type and the manufacturer’s instructions.

High-performance engines require servicing more often than other utility quads. As such, you will find that you need to adjust your ATV valves every 20 hours or so or with each oil change. 

There’s a good reason for this too. You see, if you allow the valves to go too far, the intakes become too tight and they start leaking. Then, you’ll be setting yourself up for some big-time repairs.

Additionally, depending on the type of bike you have, you might notice that the valves tap slightly when correctly set. Any noticeable sound changes would therefore indicate a need for adjustment.

  • The general rule of thumb is to stick to your manufacturer’s guidelines.
  • For example, most recommend a valve check during the 1st service.
  • This is probably because the valves are usually a bit loose from the factory.
  • Note that water-cooled engines do not require much adjustment since their clearances are way tighter.

Even so, the adjustment interval is not cast on stone. Rather, it’s what most manufacturers consider to be a safe bet between the adjustment cost and the heightened risk of valve problems or, worse, decreased engine lifespan.

Consequently, you can decide to either half or double the interval, depending on what works for you. Besides, experience and familiarity with your ATV should also enable you to diagnose valve clearance challenges.

It’s important to note that valves tend to tighten with age. With this in mind, some ATV owners suggest that you are better off adjusting on the looser end than the tighter end of the specs when making adjustments.

For detailed instructions on how to adjust your ATV valves, check out Dirt Wheel Mag’s guide. Alternatively, you can also check out this video:

Final Thoughts

ATV valve adjustments are an essential part of your ATV’s preventative maintenance. If you fail to perform the adjustment, nothing will happen immediately, but with time, additional wear and tear happen.

Again, by the time your ATV lets you know that you need to do your maintenance – noisy valves, reduced performance, etc. – more often than not, you will have done some damage already.

Rob

That's me sinking another ATV. I love to ride no matter what it is, snowmobiles, four wheelers, dirt bikes, and anything else off-roading. I've experienced my fair share of machines, and like to share that experience here.

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