How a Motorcycle Engine Works

For many years now people from all different walks of life have been brought together by one thing, one passion, and that is the power of the motorcycle engine! Of course the majority of us get on the bike and start it up without giving any thought to all the different processes that are going to make the motorcycle work, we know how powerful it is and how much petrol it gets though, but at some point when your sipping a cold beer and admiring your new Motorcycle you will ask the question 'How does a Motorcycle engine work?' So I will do my best to answer that question for you.

Basically there are two types of engine. You have the two stroke variety and the four stroke. The bigger the bike the bigger and more powerful the engine needs to be, but there are some things that can be confusing, such as: Although the two stroke engines are the smaller of the two the four strokes are the ones for the environmentalists out there as they use less fuel and therefore kinda to the environment. So smaller doesn't always mean less.

Two Stroke Engines

A Two stroke engine is made up of a piston, piston rings, crank, sparkplug, exhaust, intake port and an engine cylinder. When the piston rises up the mixture of the air and fuel is compressed and then incomes the spark plug which ignites the air/fuel mixture, this causes a little explosion within the cylinder which goes on to activate the pistons and makes the crank rotate. When the piston goes to its original placing the exhaust comes into play and leaves the exhaust port and on and on it goes at a very speedy rate.

Four Stroke Engines

Although both the Two and Four Stroke Engines comprise of a piston, piston rings, a crank, crankshaft, a sparkplug and of course an engine cylinder, unlike the Two Stroke engines, Four Stroke have multiple camshafts, lobes and stems, timing chain, intake and exhaust valves, these extras means that not only does the Four Stroke have an altered look it also has a different process as well.

The beginning of the process is exactly the same as was mentioned previously for the Two Stroke except this time the timing chain becomes involved in the process. Once the ignition has been made by the spark plug which pushes the crank and then the timing chain the chain sparks off the two camshafts causing the exhaust valve to rotate the lobe which then pushes on the stem. Once this has taken place the exhausts comes out of the exhaust pipe and just like before it all starts again with the timing chain turning the camshafts and the camshafts operating on the intake valve & lobe leading eventually to the stem being pushed causing the intake valve to open and allowing the fuel to move through the engine, setting you off on your journey! If you are looking for a modern four stroke engine please check out our main page on used Harley engines, the older Harleys used 2 stroke engines.

Motorcycle Cylinders

Something else which differs about Motorcycle engines is how many cylinders they each have. Motorcycles can have from one to six cylinders, the most popular in America, Japan and Europe was the V-twin engine for a long time, and the V-twin is loved not only for its power but for its look. The cylinders we placed in the shape of a V giving the engine a very noticeable appearance that in itself was rather appealing. Two Cylinder engines were in the limelight also for many years but it has been taken over in popularity by the four cylinder engine. The reason for this is because of their ability to give out higher revolutions per minute, unlike the two cylinder engine.

Single Cylinder Engine

Obviously as there is only one cylinder the Single Cylinder engines are much smaller, compact and simplified compared to its bigger, bulkier brothers and sisters. The problems that come with a Single Cylinder are vibration, unless balance shafts are added to help prevent this. The cooling of the engine is not as complex as that of the 'multiple' cylinder engine motorcycles and this saves on weight.

Flat Twin

The Flat Twin is an internal combustion engine. The cylinder are fixed up on opposing sides of the crankshaft and is a sub-type 'boxer' under the category of flat engines.

Flat four

The flat 4 is a four cylinder engine with the cylinders displayed horizontally. The pistons usual placing is on the crankshaft making the opposing pistons move backwards and forwards in opposite directions but at the same time. This is also known as a 'boxer' engine. The reasoning behind the nickname of 'boxer' is purely due to the engine looking like two pugilists' fighting!