The Two-Stroke Engines Quiz


By: Staff

5 Min Quiz

About This Quiz

What's more powerful - a two-stroke engine or a four-stroke engine? Think you know? Prove your engine expertise by acing this quiz!

So, let's start with the basics. All engines have pistons that perform a specific number of strokes to complete a power cycle. Four-stroke engines complete the cycle with four strokes (two up-and-down motions) of the piston, resulting in two revolutions of the crankshaft. Two-stroke engines complete the cycle with two strokes of the piston (one up-and-down motion), resulting in one revolution of the crankshaft. Two-stroke engines get the job done with fewer parts and are therefore lighter, which in turn makes the engine more efficient.

Because two-stroke engines are lighter, they are perfect for smaller gasoline engines, such as those used in lawnmowers, chainsaws and even model airplanes and motorcycles. But even when the weight factor does not come into play, two-stroke engines are more efficient, making them ideal for many applications. Even if you aren't particularly familiar with the difference between a two-stroke engine and a four-stroke engine, you'll know that you're operating a two-stroke engine when you are required to mix the fuel and the oil together.

So, you think you know enough about engines to ace this quiz? Let's get started.

Two-stroke engine oil is also known as …

Two-cycle oil is used in many small engines, from boat motors to chainsaws.


Compared to four-stroke engines, two-stroke engines tend to have what?

They're often used in small power tools and light vehicles because of their excellent power-to-weight ratio.


What kind of ignition do most two-cycle engines use?

Gasoline ignition is especially common in the smallest two-stroke engines.


How many revolutions does the crankshaft make during a power cycle in a two-stroke engine?

The crankshaft, which converts the pistons' up-and-down motions into rotation, makes one complete turn each power cycle.


True or false: Compared to four-stroke engines, two-stroke engines have a shorter service life.

To maintain their working life, staying on top of lubrication is especially important in two-stroke engines.


When compared to four-stroke engines, how many parts do two-stroke engines contain?

The lower number of parts in a two-stroke engine is the primary reason they tend to be lighter.


True or false: Two-stroke engines typically don't last as long as four-stroke engines.

Their inefficient oiling methods mean less effective lubrication shorter engine life.


How many times does the spark plug fire for each revolution of the crankshaft in a two-stroke engine?

It only fires once per revolution. This trait helps two-stroke engines produce more power, by weight, than four-stroke engines.


What is a primary inovation of the new two-stroke engine that Honda unveiled in 2015?

The point of the direct fuel injection is to reduce the amount of unburned fuel in the emissions, making them run cleaner.


Compared to four-stroke engines, what are the characteristics of emissions from small two-stroke engines?

The emissions are higher in large part due to the oil that's mixed with the gasoline.


What is another name for the oil/gas mixture in a two-stroke engine?

Petroil, or two-stroke oil mixed with gasoline, makes the total-loss oiling system work.


What color is the smoke emitted from many small two-stroke engines?

It gets its blue tint from the oil that's blended into the fuel.


Dugald Clerk's two-stroke engine was the first to do what during every revolution of the crankshaft?

It combined compression with ignition during each revolution. Clerk succeeded where other inventors had already failed.


True or false: You usually get more miles per gallon on a two-stroke engine than on a four-stroke engine.

At smaller sizes, two-stroke engines aren't really fuel efficient.


What characteristic is typical of a two-stroke motorcycle's power band?

The range of RPMs that offer peak power on these bikes, known as the power band, occurs in a very limited range.


Why are two-stroke outboard engines (for boats) NOT environmentally friendly?

These engines can leave clouds of smoke and trails of oil in the water.


Compared to lubricating oil, two-cycle oil has less …

Less ash makes burning the oil a bit cleaner.


What's an advantage of a rotary valve?

Asymmetrical engine timing often results in better power output.


How many strokes do two-cycle engines require to complete a power cycle?

Two up-and-down motions make up the stroke (and the power cycle).


Compared to four-stroke engines, how efficient are the enormous two-stroke diesel engines used on ships?

It seems bigger really is better when it comes to the efficiency of two-stroke engines.


What year was the first two-stroke engine (with in-cylinder compression) patented?

Dugald Clerk invented it in Scotland and patented his creation in England in 1881.


In a two-stroke engine, at the start of a new stroke, both the inlet and exhaust ports are …

They are both open. Air pressure differences cause a fresh fuel/air mix to move into the combustion chamber.


What is a typical compression ratio for a small four-stroke engine?

The typical compression ratio is 12-to-1. Higher compression ratios generally mean more power.


Who created the first practical two-stroke motorcycles?

Scott, who also had about 50 other patents to his name, founded the Scott Motorcycle Company in 1908.


What is the name for the upward stroke of a two-stroke engine?

The upward stroke is the compression stroke, and the downward stroke is called the power stroke.


For small two-stroke engines, approximately how many ounces of two-stroke oil do you need per gallon of gas?

You need 4 ounces of oil per gallon of gas — and it can be pricey, too.


In small two-cycle engines, where does the oil originate?

The oil originates in the carburetor and, from there, is mixed directly into the fuel.


What is a typical compression ratio for a small two-stroke engine?

The 6-1 compression ratio, which means the volume of the mixture is compressed by the piston in the cylinder to one-sixth of its original, is fairly low for small engines.


What is the most common type of inlet port on smaller two-stroke engines?

In this configuration, the piston covers and uncovers the ports as it travels up and down the cylinder. The 1970s saw significant improvements in piston-controlled inlet ports.


How do the lubrication systems on large two-stroke engines work as compared to large four-stroke engines?

The oil-fuel mixing process is mainly for smaller and cheaper two-stroke engines.


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