How Does a Honda Engine Work?

Introduction

A Honda engine is an internal combustion engine. This means that a fuel and air mixture is drawn into the engine where it is ignited under pressure. This ignition essentially creates a small explosion that drives a piston downward inside a cylinder and this, in turn, rotates a shaft to deliver the work the engine is intended to do, whether it be to run a generator or mow a lawn or some other task.

Components

The engine has a number of key components. These include a cylinder, a cylinder head, a piston, a pair of valves, a carburetor, a crank shaft, and a spark plug. The piston is at the core of the engine. It fits tightly inside the cylinder forming a seal against the cylinder walls. The piston slides up and down at high speed inside the cylinder, but it can't just do that by itself. It needs something to force it up and down. This is done by combustion as described below.

Stroke one

There are four strokes to the Honda engine. Starting with the intake stroke, the piston moves downward inside the cylinder. The cylinder head is bolted to the cylinder and forms a seal. There are two valves in the cylinder head that can open and close that seal. One valve is called the intake valve, and the other is the exhaust. On this intake stroke the intake valve is open. This allows suction created by the piston as it travels downward in the cylinder to draw in a mixture of fuel and air that is delivered by the carburetor.

Stroke two

Once the piston is at the bottom of this stroke, the intake valve closes. (The exhaust valve was already closed and remains closed for this stroke.) Next, the piston travels upward inside the cylinder. This is called the compression stroke because, with both valves closed forming a tight seal, the piston compresses the mixture of fuel and air.

Stroke three

When the piston reaches the top of its travel in the cylinde,r the spark plug sparks and ignites the fuel and air mixture. This creates the small explosion (combustion) that drives the piston downward. Since the piston is connected to a shaft called the crankshaft, this downward force turns the shaft. The shaft is connected to whatever device the engine is intended to operate---a mower blade in the case of a lawn mower and an electric generator in the case of a generator. Because the piston is connected to an offset crank on the crankshaft, the shaft continues to turn on all the engine strokes. It's the combustion stroke, however, that keeps everything moving.

Stroke four

Now, the piston moves back upward in the cylinder but this time the intake valve is closed and the exhaust valve is open. This allows the upward travel of the piston to expel burnt fuel through an exhaust port. As soon as the piston reaches the top of its travel on this stroke, the exhaust valve closes and the intake valve opens. Now, when the piston travels downward again, it has completed the cycle and repeats the intake stroke as described above.