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Isn’t it strange that we’re only now talking about motorcycle engines – after 14 episodes?
Either way – release your inner mechanic – this weeks’ episode is all about internal combustion engines.
Tune in to discover:
- The basics of internal combustion engines
- 4 common motorcycle engines, and their pros and cons
- What’s in a top and bottom parts of an engine
Transcript
Hello and welcome to 30 minute motorcycling – a podcast for new aspiring and returning riders where you’ll learn something new about motorcycles and other two-wheelers in 30 minutes or less.
And despite making 13 episodes of this show so far, we’ve forgotten to talk about one of the most important parts of a motorcycle – the engine.
Therefore, in this episode, we’re going to talk about how an internal combustion engine works.
But that’s not all – we’re also going to talk about some common engine types, some pros and cons of each one and about the top end and bottom end of the engine.
First things first though – let’s get to how an internal combustion engine works.
Internal combustion engine basics
An internal combustion engine works by burning a mixture of air and fuel in what’s known as the “combustion chamber.”
This is all part of a process known as the “combustion cycle,” which consists of the following stages:
Intake
Compression
Ignition
And Exhaust
During the “Intake” stage, fuel and air mixture enters the combustion chamber from the fuel tank through the inlet valve.
Then, during the “compression” stage, the mixture is moved up and compressed by the cylinder piston.
When the mixture reaches the top, the sparkplug ignites the mixture and pushes the piston down – this stage is known as the “ignition stage.”
And finally, during the “exhaust” stage, the burnt gases are forced out of the combustion chamber and into the exhaust system.
An easy way to remember this cycle is with this word sequence:
“Suck” “Squeeze” “Bang” and “Blow”
I’ll say that again
“Suck” “Squeeze” “Bang” and “Blow”
So now that we’ve got some basic knowledge about the internal combustion cycle, let’s move on to some common engine types.
Beginning with the single-cylinder engine:
Single-cylinder:
As you may have already figured out, a single-cylinder engine only has one cylinder.
This layout is common for many 2-stroke mopeds, dirt bikes, and motorcycles. Due to its simplicity, a single-cylinder engine is very cheap to make. It’s also very easy to work on.
However, at faster speeds, it’s not so great. So if you were thinking about taking your single-cylinder motorcycle to the motorway, think again.
Let’s move on to the Inline Engine
Inline engine
In an inline engine, all pistons are positioned vertically in line with each other, hence the name.
You often hear inline engines referred to as “inline 3,” “inline 4,” and “inline 6.”
If someone says that a motorcycle’s engine is an “inline four,” it means that:
1: The engine is an inline engine type and that
2: It has four cylinders
The inline 4 has been one of the most common engine layouts – and it’s easy to see why.
Compared with a single or even a two or three-cylinder engine, a four-cylinder engine gives you more power.
It must be said though that since an inline engine has more parts, it can be hard and expensive to work on.
If you are looking for an engine with lot of power that’s still easy to handle, the next type of engine, known as a “V-Twin” might be just the thing.
V-Twin engine
A V-Twin engine, commonly called a “V-type” or a “Twin Cylinder Engine” has at least 2 cylinders mounted in a “V-shape” – hence why it’s called a “V-twin.”
V-Twins are powerful, but not as powerful as inline engines.
V-Twins have an even power curve, making them easy for beginner riders, although some of them vibrate a lot.
And that leads up to the last common engine type we’re going to take a look at in this episode, and that is the Flat-twin.
Flat-twin engine
Just like the V-twin, the flat-twin or the “horizontally opposed twin” also has two cylinders. However, unlike the V-twin, a flat-twin engine has its pistons positioned opposite of each other.
Flat-twin engines can be powerful, but also expensive to make, and therefore, motorcycles with flat-twin engines have an equally expensive asking price.
Some bikes that use the flat-twin engine include the BMW R100, the Honda Gold Wing, and the Harley Davidson Model W.
Top and bottom ends of the engine
So now that we’ve gone through 4 common engine types, let’s finish this episode by talking about the top and bottom ends of an engine.
As I just mentioned, an engine is separated by two parts – known as the bottom and top end.
These two parts are separated by an area known as the “crankshaft assembly.” This is where the crankshaft sits, which converts the linear energy of the cylinder piston or pistons into rotational energy.
Anyway, the top end of the engine includes everything above the crankcase assembly, including:
- The cylinder or cylinder block for multiple cylinder engines
- The cylinder head
- The piston or pistons
- The intake and exhaust valves
And if the engine is an overhead cam design, the camshaft is also found in the top end.
As for the bottom end, we’ll find the crankshaft, the flywheel and other components responsible for delivering the power and torque in a reliable way.
This includes:
- The flywheel and the oil sump (which is where all the engine oil is stored)
And that concludes this episode of the 30 Minute Motorcycling Podcast.
For more information about how an internal combustion engine works, I’ve put a link to a blog post on The Dual Wheel Journey in the show notes.
In the next episode, we’ll cover the differences between 2- and 4-stroke engines, and what a “stroke” really is.
Until next time, keep your helmet on, and your eyes on the road.
