How Does Valve Clearance Affect Performance & Consequences of Bad Valve

Do you really wanna know, “how does valve clearance affect performance?” Welcome to this site, and today’s post is about the same doubt you have. How much clearance affects your bike depends on your dirt bike’s age, condition, and brand.

Also, valves are available in different types, so what kind of clearance you have will decide the function of a dirt bike. You should also know the symptoms of the wrong part so that you can replace it before it worsens. 

What is the Valve Clearance? 

I know you are here to understand how does valve clearance affects performance? You should also have a little knowledge about valve clearance.

The term valve clearance is related to the gap between the top of the valve stem and the cam that helps complete an entire cycle from starting the dirt bike to releasing the unburnt gases.

The inner side of the valve allows the air-fuel mixture into the cylinder, whereas the outer or exhaust valve removes the burnt gases via its pipe. The valve should be closed entirely during the combustion process and expansion of the gas.

If by mistake it is still open, then the hot processing can burn the seat, engine, and piston. 

Why Is Valve Clearance Important?

Valve clearance is much necessary for well performing of a dirt bike

But how it is crucial, actually when the valve is opened, the air-fuel mixture can move through the seat, and other valves present inside the cylinder. And then, the piston compressed with enough fuel and delivered power to the crankshaft. 

The valve clearance comes in different sizes and quality; please choose the appropriate one.

If you buy a bigger size and try to fit it, you will face such problems like the screwdriver doesn’t fit between the cam lock and the bucket to move correctly for perfect fitting of the valve. Even if you think that this tight valve is enough, you can’t imagine how many blenders you are doing.

More gaps will be remaining, and it can’t lock the valve somewhat, which may burn the other parts while having a combustion process. 

And on the other hand, if you fit a small size valve, there will be more gaps, which couldn’t suit the engine.

Keep a perfect gap to allow the air fuel and restrict the extra ones. Not only significant gaps cause problems. Small holes do the same. 

Symptoms of Bad Valve Clearance:- 

A red light alert near the electronic site indicates something dangerous there. But, how do you know that valve clearance is out of the service.

We have noticed a few symptoms of lousy clearance that are trying to convince you to save your bike before something worse will happen. 

Damage Other Valves-

Too much valve clearance can tear the whole valve train. It is connected with pistons, spark plugs, camshafts, rocker arms, and crankshaft internally.

You can understand that with a single connection of electricity, any wire break from somewhere can affect the whole relationship.

In the same way, if the valve is damaged, it will destroy all other parts as well. It is better to keep your attention on your clearance too. 


It is one of the dangerous symptoms of explosions. When clearance is too low or less gap in the cylinder, then air passing becomes difficult.

When enough space is there, then extra heat can flow out from the exhaust, but in this case, heat remains inside the engine and makes it hotter.

Also, less clearance affects compression, and such low compression is not achieved for the whole performance.

If you keep ignoring this issue, it causes the valve to break, and a broken valve may charge you high for rebuilding the engine. So, if you see overheating even at a cold place, better check valve clearance. 

Premature Combustion- 

Let me explain this: premature combustion means that the spark plug gets enough heat to fire before completion of the combustion process. What, when you start your dirt bike, the engine takes a few times to heat up; as its temperature rises, valve clearance reduces.

Less clearance seals the heat properly and helps in firing the spark plug. But, in case of less clearance, the engine heats quickly, and as a result, the bike starts earlier, even before the spark plug fires.

It’s not a good sign; if you face the same problem, be sure there is something wrong with the valve clearance. Ignoring it may produce unpleasant sounds and even damage the valve soon. 

More Fuel Consumption-

If the valve is not fitted correctly, the intake valve allows an air-fuel mixture into the cylinder.

If the valve clearance is too tight or loose, the exhaust valve remains open, and at the end, whatever fuel goes inside the cylinder can directly reach the exhausting system and burn in more & more amounts.

You must hear about the backfires, extra fuel present in the engine makes it possible to burn in the exhaust pipe. If valve clearance keeps in the same position, it will waste more fuel.

I know you can understand this much fuel consumption costs you so much. Please check valve adjustment to stop this problem.

Knocking Noise-

Suddenly you hear a knocking noise coming from the head of your engine. What is that? It’s a sign of a loose valve.

But, not every noise related to that, maybe you leave the engine open for a long time, and it starts producing the noise.

If you haven’t set the valve clearance at a suitable space, it disturbs the whole valve train, and that string develops an annoying sound.

It will be an excellent job if you take such sounds seriously and at least have a look towards the clearance. As you know, loose clearance can cause a lot to you; even it will affect the acceleration and later performance of dirt bikes. 

If you have any of those symptoms, don’t ride a bike. Having the same signs can burn your body, too, as seats can be exploded. Overheating is the most common symptom, ever happens to your dirt bike; shut it down and show the mechanic.  

You must read : How To Check Valves on A Dirt Bike?

Can Valve Clearance Cause No Start?

If the valve clearance is too tight, less the clearance is there, and no power will be passed to the crankshaft.

When the valve is not working, the top of the cylinder gets heated, and it’s too hard to seal the leakage gas with an insufficient valve clearance.

Initially, even without the firing generated by spark plugs, the engine starts earlier. But, gradually, it’s losing the quality and hence tear the valve train or fire can be taken due to excessive heat inside the engine’s cylinder.

All over, an inadequate valve clearance can cause no start and also can wreck your dirt bike. 

How Often Should Check Valve Clearance?

As people said, eat an apple a day and keep the doctor away. Why not follow the exact instructions here. Before the valve clearance goes bad, keep checking to avoid significant harm.

I mean to say why you need to check the valve clearance when you see the symptoms; it’s best to inspect after every 5000 miles. If you keep maintaining your dirt bike, you should also include valve clearance.

This good habit will elongate the life of your bike and its parts. And the important thing is to check the intake clearance should be 080 inches, and for exhaust, it would be 100 inches and keep an extra exhaust valve as it expands a lot due to heat transfer from the combustion. 

What Process Includes Changing a Valve Clearance? 

Have you found anything similar to the bad valve symptoms? If yes, then try a few steps to do the valve job. Remove the cylinder and valve train one by one and clean them properly. Now, check the head of the cylinder, is there any damage, cut, or crack? Note it down.

Later, inspect valve, springs, camshaft, seats, and whole valve train parts, anything tear there or damage. You can reuse the valve train if the damages can be fixed by cutting or separating the components or you need to replace them.

The next point is if any problem is in the cylinder, change it immediately. After making all parts perfect, reinstall in the reverse process of removal. 

How Much Does A Valve Clearance Cost?

Valve clearance charges about $67 to $70; if you fix it by yourself, it will cost less. But, if you are thinking of visiting a repair center, they charge you per hour. Adjusting valve clearance takes a minimum of two hours, about $200-$400.

So, it’s advisable not to waste too much amount and fix it with our help. But, still, you won’t be able to replace it, then it’s better to show a mechanic. 


Ignoring the valve clearance damages will lead to a major accident, don’t avoid it. If you invest a large amount in purchasing a branded bike, why can’t you maintain it?

Also, keep checking the valve, piston, spark plugs to rescue higher loss. 


Using a bad valve can cause rough idle bikes and also produce tipped sounds. To stop any further damages you have read this article which is going to help. 

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