Continuously Variable Transmission

What is a CVT or a Continuously Variable Transmission? It is an Automatic transmission that can change gear ratios depending on vehicle speed, engine power or RPM and load. Engines have different RPM range where they deliver engine best power and engine efficiency. Its purpose is to allow the engine operate in an optimal power for varying driving conditions. It consist of three different components, a Primary Clutch, Secondary Clutch and a Belt. The primary clutch has two faces which are the stationary sheave that is connected at the engine crankshaft and a movable sheave that works in and out to engage the belt. The same with the secondary clutch is has also a stationary sheave and a movable sheave.

Lets start with the Secondary Clutch, this is where you can find the flyballs or rollers and ramp plate locations. As the throttle is depressed, the engine revs increase, centrifugal force pushes the flyball weights outward and up the ramp-plates surface. This will cause the sliding variator to move toward the outer fixed pulley half. As the variator slides closer to the Secondary Clutch it applies pressure to the drive belt that sits in between the angled faces of the front pulley half and the variator so that it forces the belt out to a higher gear ratio. This is the basic operation of the Secondary Clutch. Higher engine top speeds cause the belt to go outward changing the gear ratios.

Moving onto the Primary Clutch, has a center spring that holds together the halves of the Primary Clutch. Center spring is a large and powerful spring that make sure that the gearing is at correct level. Its has also three clutch springs that allows the clutch to bite. The front half of the Primary Clutch is placed under pressure by the center spring to make sure that the best gearing is at best tension. There are angled grooves that the pulley travels on, this is to ensure that the gearing ratio is not affected by the belt travelling at high speed.

2-Stroke VS 4-Stroke Engine

Maybe from past days or years you have own a 2-stroke engine motorcycle or if not you have seen someone owning one. Even scooters are available in 2-stroke and 4-stroke engines. The question will be, how the 4-stroke is better than 2-stroke? Why does manufacturers now stop launching or releasing any 2-stroke engine motorcycle anymore? This question will be answered in this thread and hope to help you to find for the information you are looking for.

First of all lets define what is the meaning of the word "stroke". Stroke is the movement of the piston in the cylinder back and forth. The length of the stroke will be determined by the crankshaft or the distance travel of the piston in the engine cylinder. The 2-stroke engine has two strokes to complete a power cycle. The end of the combustion and beginning of the compression stroke happen simultaneously, with the intake and exhaust stroke occurring at the same time. This is a contrast when it comes with the 4-stroke engine that needs four strokes to complete a power cycle.

Advantages and Disadvantages

2-strokes have a high power performance in comparison with the 4-stroke. Also the 2-stroke has few moving parts that makes it lighter and simplify their structures. This engine type also have a low cost for maintenance. The disadvantage of this type of engine are lot more than its advantage. This engine type don't last that longer and lubrication is needed for the mixture of fuel gas. Poor lubrication may caused the engine to wore out even more faster. It may cost a little bit that it almost consume a gallon of oil in every 1,000 miles. The fuel economy with this engine is not that good as part of the mixture leaks out in the exhaust port because the intake and exhaust process occurs at the same time, making more pollution than other engine types.

The 4-stroke engine has better fuel efficiency than the 2-stroke engine. Less pollution and you can save more in terms of fuel consumption. You don't have to buy gallons of oil to keep it working that help you also to save more. This engine last longer than 2-stroke and durable for use. Has more torque making your engine quitter and more reliable performance. The disadvantages are 4-stroke engine cost much higher than the 2-stroke, maybe because of the materials and components use also its system. 2-stroke engine has more power making the 4-stroke only with half of its power in comparison. This engine is more complicated because of some additional parts in the mechanism like valves. Making this engine hard for troubleshooting and cost more higher.

How 4-Stroke Engine Works

Most of us have heard about a 2-stroke and a 4-stroke engine, but do we all know how really this engine works? Every vehicle needs an engine to provide the power for the said vehicle. The combustion that happens in our engine is responsible for the power we get from the vehicle that make it run. I will explain some of the details and information about a 4-stroke engine. First I will tell you the parts of an engine and then explain how these parts accordingly with the other parts.

Engine Cylinder

This the part where the combustion of the fuel and air mixture happens. This is a space where the piston travels. Commonly engine cylinders are typically cast from cast iron or aluminum before proceeding in a machine that polish the cylinder. Most cylinders now are made of Aluminum that really helps for faster and easier break-in. In the process of break-in of the engine, a simple irregularities in the break-in period may cause a ware in the cylinder sleeve. If later on it continues to wear the cylinder sleeve, you will come up reboring. Reboring is the process were you need to increase the diameter of the cylinder and piston rings.

Engine Valves

The one that control the timing and mixture of air and fuel that flow to the engine. The one also responsible for the outflow of burned gas after combustion. There are two type of valve, the intake valve and exhaust valve. The valve have components when installing in the engine, the stem oil seal, spring and the lock that holds the valve in its place.

Spark Plug

This is the one that transfer an electric current in the main chamber that ignite the fuel and air mixture.

Crankshaft

The part that converts reciprocating motion to rotation motion. This part is the one responsible for the push and pull movement of the piston connected by connecting rod.

Engine Piston and Piston Rings

A component for reciprocating engines or compressors. The piston is the part that moves to compressed the expanded fuel and air mixture inside the cylinder. Contains of piston rings usually compression rings and oil seal ring. These ring help the piston for covering and uncovering ports in the cylinder wall.

Connecting Rod

In an engine this part is the one that connects the piston to the crankshaft. With the help of the crank they form a simple mechanism that converts reciprocating motion to rotation. Its the one that push and pull the piston inside the cylinder.

These are the parts that is responsible in the combustion process inside the cylinder. Now I will explain how a 4-stroke engine works. There are 4 cycle in the process of combustion, the intake, compression, power and exhaust.

Intake

When the piston move downwards the intake valve is open and allows the flow of fuel and air mixture inside the cylinder. With the help of a cam lifter it will push the intake valve to open and keep the exhaust valve close.

Compression

In this cycle the piston moves upward compressing the mixture and the pressure produced by the compression shuts the intake valve. The piston move upward compressing the mixture and until before it reach the top part of the cylinder...

Power

At the end of the compression stroke before the piston reach its highest peak the spark plug  ignites producing electricity that burns the compressed fuel and air mixture. The force produced by burned gas pushes the piston downward.

Exhaust

When the piston reach the bottom, the exhaust valve and the piston upwards to push out the burned gas form from combustion. Then the cycle repeats and repeats.