Valve tightness is the key to a 4 stroke engine. What is the sliding together that comes with cylinder head OH??

Intake and exhaust valves are important not only for the efficient flow of intake and exhaust air, but also for keeping the combustion chamber airtight. And when focusing on airtightness, the most important thing to focus on is the contact between the valve seat and the valve face. When the valve seats are worn out, internal combustion engine modification is necessary, but if it is just superficial carbon deposits or dirt, airtightness can be restored by sliding them together.

What is the content and purpose of valve seat cutting and sliding together?

The exhaust valves on the Kawasaki Zephyr X. Since the Zephyr X has 4 valves compared to the Zephyr's 2 valves, the diameter of each valve is naturally smaller. After the valve seats were pressed into the cylinder head, the matte surface on the inside of the seat became the contact surface with the valve face. If the contact surface is gouged by hard carbon sludge, the valve may not remain airtight even when closed.

The most important thing for a good compression is that the mixture does not escape from the intake and exhaust valves and piston rings when the piston reaches the top dead center of compression. Even with tuning parts such as high comp pistons and high camshafts, if compression is leaking from the combustion chamber, it is ruined. When the intake valve opens, the air mixture flows into the cylinder, and when the valve closes and the piston rises, the compression increases. However, in a high-revving engine, the opening and closing of the intake and exhaust valves is only momentary and continues for a long time.

In order to keep the mixture from leaking from a valve that opens and closes at high speed, it is important that the valve seat and the valve face are in good contact when the valve is closed. Although the contact time between the two is very short, the condition of the contact surface is important because the compressed air will try to escape through even the smallest gap if there is an escape route.

With age and carbon bite.When the surface of the valve seat is damaged, if the damage is more serious, we will ask the internal combustion engine shop to perform a process called valve seat cutting.This is the process of cutting the valve seats with a special cutter. In this process, the valve seat that is press-fitted into the cylinder head is cut with a special cutter to improve the air tightness with the valve face. At the same time, it is possible to change and adjust the width of the contact with the valve face and the contact position of the face.

in contrastSliding the valve is a DIY task that can be done by the user. The purpose is still to improve the airtightness and recoverand it is effective for the cylinder head to the extent that valve seat cutting is not necessary. Intake and exhaust valves open and close at high speed, so it is often thought that something does not get caught between the valve seat and valve face, but it is not uncommon to find carbon contamination biting into the seat surface when the valve is removed from the cylinder head. The purpose of valve sliding is to polish the contact surface between the valve seat and valve face with compound to remove such dirt and restore air tightness.

Sliding match performed with valve compound and tachometer

Valve compound and tachometer are special items that only come into play when sliding the valves together. However, they cannot be replaced by other tools, so they are a necessity when disassembling the cylinder head. The tachometer is often sold as a set of two.

Apply the valve compound to the valve face. You don't need to put too much compound on the valve face because the only area that needs it is the contact area between the valve seat and the valve face. If you apply too much compound to the valve stems, it will damage the valve guides, so it is better to apply too much than too little.

When removing the valves from the cylinder head, make sure to distinguish them so that they can be installed in the same position. If the valve and the shim are mixed up, it will be troublesome to adjust the valve clearance after restoration. If the valve diameter is small, you can use your thumb and middle finger to turn the tachometer and your index finger to push the tachometer.

In order to restore the condition of the contact surface between the valve seat and the valve face, a compound is applied to both contact surfaces and then the contact and valve are rotated to remove dirt and prepare the surface. The abrasive used for this purpose is valve compound, and the tool used to strike the valve against the valve seat is the valve wrapper, or tachometer.

Like sandpaper, paste compounds come in different coarseness, and the most commonly available ones at tool stores are medium- and fine-grit sets. The decision to start with a medium or fine compound depends on the condition of the valve seat, but just like when you polish a painted surface and the surface is rough, using a super fine compound for finishing will not be effective.

After applying a thin and even layer of valve compound to the entire circumference of the valve face, suction the valve to the tachometer, insert it into the valve guide, and rub it against the valve seat. There are many ways to do this, such as sliding both hands together like flying a bamboo dragonfly and tapping the tachometer against the valve seat, or turning the tachometer with the thumb and middle finger and tapping the tachometer against the valve seat with the index finger, but it is important to turn the valve with the compound on it while holding it against the valve seat. It is important to turn the valve while holding it against the valve seat. It is important to turn the valve seat while holding it against the valve seat. The valve compound applied to the contact surface will be crushed by the sliding contact surface and pushed outward from the contact surface as the valve is turned.

However, do not apply too much because if it runs through the valve compound valve stem and bites into the valve guide, it may scratch the inner surface of the guide and cause oil drop where engine oil flows in from the cam side.

The cylinder head in the image is for Zephyr X. Even a φ16mm tachometer seems to stick out from the valve outer diameter, and it comes off after hitting the valve seat a few times. In such a case, there is a way to put a tube on the end of the valve stem and turn the valve with a drill while sliding it together. You can connect a long, soft hose and rotate the valve with the valve open, then intermittently press the valve against the valve seat from the combustion chamber side, which will have the same effect as tapping the tachometer.

If the valve diameter is smaller, even the smallest suction cup on a generic tachometer may not be able to hold it. You can cut the outer circumference of the suction cup to make it smaller in diameter to deal with this problem. ......

Another method is to insert a rubber tube into the end of the valve stem and turn it with your finger or a drill. The tubing should be somewhat long and flexible so that it can be pressed against the valve seat as the valve is rotated.

You can see the effect of sliding together with Mitsumei Tan and the condition of the valve seat.

By applying the paste Kwangmyoudan to the valve face and pressing it against the valve seat, the condition of the hitting surface and the hitting width after sliding together can be checked. If the valve seat does not leave a vermilion trace of the Kwangmyoudan, that part of the valve is lower than the others and the valve is not closed.

On the contrary, by applying Mitsumei Tan to the valve seat, the hit width of the valve seat is transferred to the valve face. If the contact width is wider than the standard value and also closer to the center of the face (closer to the valve stem), the surface pressure when the valve is closed decreases and the effective diameter when the valve is open also decreases. In such a case, ask an internal combustion engine shop to cut the valve seat.

When the contact surface between the valve seat and valve face becomes a linear matte state by removing dirt with a medium compound and crushing the polishing marks with a fine compound, check whether the contact state is uniform or not using Komei Tan.

Take a proper amount of powdered Kwangmyungtan and melt it with engine oil to make a paste, then apply it to the valve face and press it against the valve seat. Then the Kwangmyungtan on the valve face will be transferred to the valve seat, and the width and contact condition of the seat will be visible.

If the stripes on the valve seat are constant and connected all the way around, there is no problem, but if the stripes are broken or increase or decrease in width, the valve seat surface may be rough due to carbon bite, or the valve stem may be slightly bent and the valve face is unevenly hit. It is recommended to have it checked in detail.

Also, even if the valve seat stripes are neatly connected all the way around, if the width of the stripe is not within the standard value, internal combustion engine machining is required. In the case of the Zephyr X, the standard width of the intake and exhaust valves is 0.8 to 1.2mm. As the valve seat is repeatedly struck by the valve face each time the valve opens and closes, the contact width gradually increases. If the valve spring tension is the same, the pressure applied per unit area (surface pressure) will decrease, causing the valve to become less airtight. The advantage of using Komei-Dan is that you can check not only the contact condition between valve seat and valve face but also the contact width at the same time.

On the other hand, there is a method to check the real airtightness by injecting kerosene into the combustion chamber where the intake and exhaust valves and spark plugs are installed. In this case, it is important to remove the highly permeable kerosene thoroughly before checking, as it will leak even if only a small amount of compound remains on the surface where the valve meets.

When you have a chance to disassemble a 4 stroke engine, you should prepare a valve compound and a tachometer. If you have a chance to disassemble a 4 stroke engine, why don't you prepare a valve compound and a tachometer and try to align the valves?