1. Internal structure

As a subdivision of the internal combustion engine, the difference between the motorcycle engine and most gasoline engines after removing the transmission mechanism is that the structure is more compact and the internal structure is more refined.

But even so, its main components are much the same, which mainly includes crankshaft connecting rod mechanism, valve mechanism, cylinder block, piston, piston ring, piston pin, piston spring and so on.

The valve belongs to the valve mechanism, which is generally divided into the intake valve and the exhaust valve, the working mode of the two is open and closed, the shape is the same but the size is different. Normally, the intake valve is large and the exhaust valve is small, because the intake volume is more important for the internal combustion engine, and thus there is a transition from self-priming to the turbine. (Please remember this knowledge)

And the main parts of the valve are camshaft and rocker arm and spring and other more compact accessories.

2. Basic principles

Driven by the timing chain or the ejector rod, the convex and concave surface above the camshaft when it rotates will force the rocker arm to press down or move up, and then realize the opening and closing of the valve, and finally achieve the effect of suction and exhaust, laying the foundation for the next work cycle.

It is also because of the difference in the form of the drive camshaft, there will be the difference between the small chain and the top rod engine.

It is worth noting here that the current scooter is basically the timing chain to drive the camshaft for gas distribution, but there will be a difference in the number of camshafts, some for one, some for two, this is another knowledge point, it is also closely related to the number of valves you are concerned about.

3. Good quantity

This is where we get to the point. Remember the saying that the front intake valve is bigger than the exhaust valve? This is mainly designed in order to increase the intake volume, and its theoretical support has created conditions for the later application of four valves.

Of course, in addition to the common two and four valves, in fact, there are three valves (five valves), this design and the structure of the human body has been almost, belongs to two nostrils inhalation... So everything is the same origin, as long as you look carefully at the relationship between them is still more wonderful.

The advantages of the two valves are simple structure, low cost and high stability.

After all, the more complex the machinery is, the higher the failure rate will be, and the corresponding manufacturing costs and difficulties will increase. But in order to achieve the desired performance, it can not be so much, and then there are four valves.

The advantage of the four-valve is that the intake and exhaust volume is larger, and the work efficiency is higher in the high-speed state, but there will be more obvious shortfalls in the low-rotation state, because the closing and opening efficiency is low, so there will be insufficient combustion drawbacks (mainly affecting the gas ratio), so that this type of model will have low torque and slightly higher fuel consumption.

So strictly speaking, no one is better than the other between the two valves and the four valves, and for the Buddhist cyclist they are exactly the same, and on the small pedal you may not feel the difference between them at all.

But there is no way, the four-valve has now become the mainstream, if not like this public opinion tilt, it will be labeled as not understand the car.

This is mainly because the four valves do have a limited displacement, which can further enhance the power, and will give people a sense of tall in quantity and technology.

But in fact, in the valve mechanism on the variable valve is the real king, especially when the double top camshaft four-valve valve mechanism into this technology, it is simply a seamless combination, it can take into account the innate advantages of four valves, but also to make up for the deficiency of the day after birth, can completely achieve the ideal effect of strong start and sufficient aftershock.

It is only a pity that there are not many small displacement scooters that apply this technology at present, and Yamaha's 155 series has achieved mass production (single camshaft and four valves). After all this, do you still simply think that four valves must be better than two valves?

I don't think so anyway. Because there are many factors that constitute the performance of the engine, it will also be related to its own speed, the working efficiency of the valve mechanism, the accuracy of the oil supply, the ignition ability and other factors, not only depends on the number of valves, so it is still objective and rational to look at it.

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