Motorcycle Glossary

KTM Motorcycle parked

Motorcycle Glossary: Terms & Definitions Every Motorcyclist Should Know

2T vs 4T oil

2T oils are 2-stroke engine oils whereas 4T oils are 4-stroke engine oils. Both these oils are not interchangeable since both are specific to their engine types, and 2T oils are mixed directly with the fuel whereas 4T oil is added separately.

Ash deposits

Ash deposits are white sandy soot on spark plugs. They are concentrated on the electrodes and can over time affect spark plug performance.

Battery tenders

Battery tenders are devices that keep your motorcycle battery charged at the optimum level along with some advanced features over a regular charger. Think of it as a ‘smart charger’. For example, a trickle charger doesn’t turn off automatically when the battery is fully charged. But the battery tender does.

Catalytic converter

A catalytic converter is an exhaust component (fit inside a muffler) designed to reduce harmful emissions coming out of the motorcycles.


Chopper motorcycles are custom motorcycles with high handlebars, extended forks, wide rear tires, and low seats as their typical features. The Chopper name originated in the late 50s when the custom motorcycles had their unnecessary parts ‘chopped’ off to make the motorcycle fast.

Cold start

Cold start is when the vehicle engine doesn’t start due to cold weather conditions and/or low-temperature environments.

Curb weight

Curb weight is the factory-installed motorcycle weight along with essential consumables (oils and coolant) and fuel at 90% capacity.

Dry clutch

A dry clutch is a clutch without any contact with the engine oil. Unlike a wet clutch that is immersed in engine oil.

Dry weight

Dry weight is the factory-installed motorcycle weight. Dry weight does NOT include any essential consumables like oils, coolant, and fuel.

Engine blowby

Engine blowby is the fuel mixture trickling down in the combustion chamber along the gaps between the piston and the piston rings.

Engine braking

Engine braking is decelerating the motorcycle by rolling down the throttle. Instead of applying brakes.

Engine CC

CC is a measure of the volume capacity of an engine cylinder measured in cubic centimeters. The volume capacity of the engine cylinder is calculated by multiplying the bore area with the stroke length.

Engine compression ratio

The compression ratio is measured as the volume of the combustion chamber when the piston is at its lowest point (BDC – Bottom dead center) to when the volume when the piston is at its highest point (TDC – Top dead center).

Engine guards

Engine guards (also called crash bars) are hoop-shaped bars usually mounted on motorcycle frames at the front in order to protect the engine mainly and also to protect the rider from accidents at slower speeds.

False Neutral

False neutral occurs when you shift the motorcycle gears but the gear does not get engaged – resulting in an unstable neutral position.


Thin protrusions on the engine’s outer layer are called fins. Engine fins. They are designed to help the engine cool down by speeding up the heat dissipation process.

Fork oil

The fork oil is the oil that goes in the front forks of a motorcycle and acts as the shock absorber. FYI, fork oil is not the same as engine oil.

Gas mileage

Gas mileage is the measure of the distance traveled by a motorcycle consuming a unit amount of fuel. The most common gas mileage measures are MPG (miles per gallon) and km/L (kilometers per liter).

Glow plug

A glow plug is an electrical heating component fitted in diesel engines to preheat the engine combustion chamber. They help in starting the diesel engines, especially during cold starts.

Gross vehicle weight (GVW)

Gross vehicle weight (GVW) is the total vehicle weight including the curb weight, cargo, other equipment and accessories, and the rider and passenger.

High beam

The high beam is a long-distance beam which is narrow in pattern but lights up the distance far away.


Harley Davison riders are called Hogs. The nickname Hogs came from the motorcycle racing days in the early 1900s.

Hot spark plugs vs Cold spark plugs

Hot spark plugs have more insulation close to the tip which reduces heat transfer and maintains a high temperature in the tip.

Cold spark plugs, on the other hand, have less insulation close to the tip, leading to more heat transferred away and reducing the tip temperature.

Kill switch

Kill Switch is a red color safety mechanism button on the right side of the motorcycle handlebar. The kill switch is used to quickly shut down the engine and switch it back on without reaching for the keys.

Knee scraping (knee down)

Motorcycle knee scraping is when the motorcycle racer lowers his knee to the ground by leaning his/her racing motorcycle. Knee scraping is also called knee down and knee dragging.

Oversquare vs Undersquare engines

If the piston stroke length is larger than the bore diameter, the engine is called an undersquare engine. And if the bore diameter is larger than the stroke length, the engine is called an oversquare engine.

Lean angle

The angle at which the motorcycle is leaning with respect to its vertical position. MotoGP riders claim to achieve a maximum lean angle of a 64º (that’s freaking huge).

Lean fuel mixture (running lean)

Lean fuel mixture refers to a high proportion of air for the amount of fuel present in the air-fuel mixture. In short, too much air and too little fuel. When the engine runs on a lean fuel mixture, it is said as running lean.

Low beam

The low beam is a spread beam where the light falls close to the motorcycle and is wide in the pattern.


A muffler is an exhaust component that reduces (muffles) a loud sound. It is the last part of the exhaust through which the exhaust gases escape into the atmosphere.

Pass light

A pass light is a temporary light that switches the high beam on momentarily. The pass light is used to notify the other vehicles of your presence.

Rain sock

A rain sock (also called an air filter cover) is a thin cover designed to prevent water and dust from entering the air filter.


A rectifier is an electronic device that converts alternating current (AC) to direct current (DC).

Resistor and Non-resistor spark plugs

Resistor spark plugs are those spark plugs that have a resistor in their center electrodes.

Non-resistor spark plugs, on the other hand, do not have any resistor on their center electrodes.

Rich fuel mixture (running rich)

Rich fuel mixture refers to a high proportion of fuel amount for the air present in the air-fuel mixture. In short, too much fuel and too little air. When the engine runs on a rich fuel mixture, it is said as running rich.


The silencer (also called muffler) is the last part of the exhaust through which exhaust gases escape. The silencer reduces (silences) the exhaust gases sound.

Spark plug

A spark plug is the component used to ignite the fuel mixture in gasoline engines. The spark plug produces a high-voltage spark to ignite the fuel in the engine.

Speed wobbles (tank slappers/ death wobbles)

Motorcycle speed wobbles are caused at high speeds when the front tire loses traction and the handlebar starts to oscillate violently.


Stalling is when your motorcycle comes to a sudden halt because of insufficient power transmission from the engine to the rear wheel.

Straight pipe exhaust

A straight-pipe exhaust in a motorcycle is an exhaust pipe running from the header to the end without a muffler and a catalytic converter.

Throttle blipping

Throttle blipping is when you turn the throttle up and simultaneously lower the gear (downshifting) to maintain a good speed in the motorcycle. The usual steps are – you pull in the clutch, downshift, rev the throttle at a time, and release the clutch.

Thumb throttle

The thumb throttle is a throttle setup with a spring-loaded lever that accelerates the bike when you push the lever using the thumb. Commonly used in ATVs.

Twist throttle

Twist throttle is a setup that throttles up or down (accelerate/decelerate) depending on your wrist movement on the throttle. Commonly used in motorcycles.

Wet clutch

A wet clutch is a clutch immersed in engine oil. Hence the name – ‘wet’ clutch. Unlike a dry clutch that does not come in contact with the engine oil.

Wet weight

Wet weight is dry weight plus consumable fluids like oils, coolant, and fuel. Wet weight is nothing but the curb weight itself.