How Does Valve Clearance Affect Performance – Tight vs Loose Valves

You may wonder how does valve clearance affects performance whether it is tight or loose valves. This is a model I am with to be able to explain to you why valve clearance is extremely important on a four-stroke more cycle of the valve. Valve clearance is something no one can ignore, if ignored he will end with many issues related to valves haunting your dirt bike.

We have brought here a brief explanation describing how a valve clearance is important and certainly, it affects the dirt bike performance in many aspects. Performance required from a bike can be high and if not achieved then it is not worth it.

How Does Valve Clearance Affect Performance?

why is valve clearance important

Being a beginner if you don’t know what is valve then you can go through this article first. A valve shim is very very important in the makings of almost any dirt bike and even cars. Mostly for the motorcycle in high R. P. M. engines develop shim is the green peace that you could see right over here.

How Does Valve Clearance Affect Performance motocross

These basically come in different sizes and you need to know why they are important for a bike. In this case, what I have over here is that this is the valve and there is the valve shim, this is the valve seal and guide this is the head of the motor this is the bucket in some manuals you could find it under different names Valve retainer valve holder. This is the shim over here and this is the cam.

How Does Valve Clearance Affect Performance motocross

Now what happens is that when the motor turns the valves open with the motor does the job of the campus to open the valve so what happens is that when the cam moves the valve opens here at the bottom and then once the lobe of the valve goes out the valve basically closes.

When the valve is opened the fuel can travel between the seat and the valve into the cylinder and then the piston can create the compression and you get power. When the motor is cold you have to have certain gaps in certain places of the motor because when he eats up those distances those clearances change. In this case, over here you could see that I could clearly fit the screwdriver under with no problem whatsoever.

If I change the shim to a bigger shim so I’m gonna change. This share into a bigger shim at this point what happens is that not only did the screwdriver doesn’t fit in between the cam lock and the bucket because of the size of the shim but also I have a gap over here at the head so the motorcycle right now will not be able to close the valve properly.

If I have two small shims like this one that’s going to happen you can have too much gap between the cam lock and the bucket for the valve.

Therefore even though the valve is closed over here there is too much gap in here and win the Cam-lock comes around it hits the valve re really hard.

That’s where you usually hear of valve ticking because there is too much gap and when the valve cam lock comes in it basically hits it in the head So this is why this little shims that are located on the here are very very important because what they do with their job is to keep the valve basically flush to the cam lobe when the motor is warm.

That’s why you check for clearances for the valve on the cold water because the manufacturer calculates these things and he knows that on a cold motor the clearances for the gap over here have to be between certain numbers.

Once the motor warms up basically this gap closes because the stem of the valve expands the motor has expanded.

Basically everything around the motor expands and they know that once the motor is warm if you have the right clearance over here when it’s cold basically the cam lock will be flush with the valves and go for the cam lobe will travel over the bucket the whole of the shim in and it will not basically keep it and hid in the head.

If you have too much gap or we have too little gaps that could cause all kinds of problems. Not having the right clearance on the cold motor between the bucket and the cam lock can call several problems.

Tight vs Loose Valves

How Does Valve Clearance Affect Performance motocross

I’m gonna explain to you the two scenarios that are the most common. Right now as you can see we have a perfectly good gap in between with no problem whatsoever but let’s say that your valves are out of specifications. So then your shim is not right so I’m gonna change this shim to bigger shims of this is a bigger share right now.

Automatically when I put the bigger shim over here the clearance gap on cold bike disappears right so I can up with a screwdriver through here.

If you don’t have a clear it’s over here what happens is that the bucket the shim and the valve stem rest on the cam lock if the rest on the cam lob what you are gonna have. These you gonna have always a gap here in the front between the valve seat and the valve itself.

So this valve is not properly closed if there is fuel and gas in the top of the motor over here when you are kicking the motor or trying to start it from that you start this valve will never properly close or open and if it’s not properly closed or open it will always breed false air so you could never achieve the proper compression for the more to run properly.

This will not create any damage to the motor except a little bit of a warrant here on the valve little bit self because every time it spins what it does it moves the valve down so the valve will go down and did the developer go off pushed by the spring and then it will move over and over and over.

Every time this motion happens you always going to maintain a certain clearance over here so this valve will always be open and because it’s always open you have a motorcycle start would be hard usually.

This is something that you see a lot on the Honda motorcycles it seems that a Honda motorcycles the valves tight all the time and when you have a type valve there is a perfect symptom did you have a motor that is breeding falls aired through the seal of the year and then you have a motorcycle starts really hard.

What happens when you have a valve that is loose? When you have a loose valve basically have too much gap here at the top and this can be achieved by a shim that is not the right size right now I’m gonna put a very very tiny shim on the top of the motor over here so you could understand.

So right now it’s exactly the opposite of what you just saw before now we have too much gap over here on the cold water and then in the valve, it is nice resting on your valve seats. So this is a sealed system right now fuel cannot travel through and you’re thinking well that must be a good thing. Not so fast actually this is the worst situation you can have on a motorcycle.

Did you try to start a motorcycle the motor will warm up and when it warms up this gap is specifically designed over here so it can be closed by the expansion of the materials in the motor to where the bucket travels on the lobe of the valve a camshaft all the time?

The problem in this situation is that if you have too little of a shim over here two small shims up to lose all the valve the lobe when it comes over and opens it available open properly so the fuel can travel through here with no problem whatsoever but when it closes the valve here will not be able to rest on the cam lobe.

So right now you have a loose bucket and then it is going to be a problem it’s two reasons well first of all when this bucket is loose that means that all the pressure from the spring that pushes the valve up is going to rest on the seat of the motorcycle to the seat in the head is going to be a problem because the valve would basically rob on the seat every time the valve goes up and down.

So this is going to create a lot of premature wear and tear on the valve itself and on the seats so one or the other will win it depends which one is stronger if yet titanium valves usually develop the to be replaced after you running the dirt bike like this for a long time.

If you have to steel valves then the seat will be replaced we need to be replaced and that’s going to be even more expensive than replacing the valves because you have to send the head out to get the seat knocked out and replaced.

So having a too much of a gap having a loose valve it’s actually one of the worst things you can do on your motorcycle also it has a secondary effect it makes it even worse as I explained before when the cam lobe comes over and pushes the valve, the valve opens here’s to the bottom the problem is that when the valve travels at high RPM the valve lobe will spin this way in the spring will throw the valve back into the seat.

Not only you creating wear and tear over here but what happens is that the bucket, because there is too much gap over here would actually float so, will flow then hit the cam lobe. When it floats it creates a distance here at between the shim and the valve stem.

And this is a big problem because once the valve bucket is floating when the cam lobe comes back and hits it this distance is gonna be cut really fast and what happens is that at this point this cam lobe will keep hitting the stem and will either create gap into the valve shim or worse usually does what happens is that on the titanium valves the cam stem will automatically get worn out like hitting a nail in the head.

So you know like when you have a nail and you hit in the head too many times it just gets flattened like this, This was going to happen so the gap is only going to grow bigger and bigger and bigger to a point where this valve is going to be absolutely useless you gonna have so much gap then you can clearly see a ticking noise when your dirt bike runs.

This will put the wear and tear on the valve on the top and at the bottom. This is gonna be due for your motorcycle valve that’s why it’s so important to have the ride gap for your Shims. So that’s why you have this shims on the top of the motorhead.

Well, what happens is if you put the right gap which is the medium size of the shim, in this case, the motorcycle when the motor is warm the motorcycle will not have a gap over here at the top so what’s going to happen is that with the right shim, in this case, I will put the perfect size shim in here. So with the right shim when the motor is warm when the valve came comes over it will open it up.

It will close and 2 things will happen right now this will rest on the cam lobe but there’s gonna be no gap over here for the valve to be get damaged and then when this the cam lobe comes back in there’s gonna be no distance for this one to move around and it would just nicely push it for an open it and close it.

So basically this bucket with travel over the lobe all the time also because the distance is right when the more is warm the valves will close but it will close so good that it will barely rest on the seat. The valve would not get a worn out and therefore your valves would last a lot longer.


If you have a dirt bike, this is very very important to know about what are the valves, they could get loose and they could get tight that’s why the clearances are there. They’re very very important for a bike and this is the best way that I can explain it.

Not checking the valve clearance it’s one of the worst things that you could do for your motorcycle is very very simple well you have to do is just pull this the ship out, put another ship in there and then once you have the proper clearance over here on the cold water then you more cycle should run for a very very very long time.

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I’m Thomas. Since childhood, I am fond of bikes and hence dirt bikes are my passion now. Ever since then, I’ve been giving advice to the beginners and this has become my hobby.


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