Motorcycle Glossary

2 second rule - The 2-Second Rule is the minimum spacing in seconds between moving motorcycles. While in formation, maintain a 2-second interval from the rider in front of you. Measure the time by counting "one-thousand one, one-thousand two" as you see the rider in front of you pass a sign or landmark. Stop counting when you pass the same marker. Under poor weather conditions, maintain longer intervals consistent with safety.

4 stroke - A 4-Stroke is an engine that uses four strokes to complete a complete cycle. The four strokes are: Intake, Compression, Combustion, and Exhaust. During the Intake Stroke, the intake valve opens and an air-fuel mixture enters the chamber above the piston. The piston moves down drawing the mixture in. The intake valve then closes and the piston moves up for the Compression Stroke compressing the mixture. The spark plug then ignites the mixture causing an explosion. The resulting force moves the piston down again for the Combustion Stroke. Then the exhaust valve opens as the piston moves upward for the Exhaust Stroke and all the exhaust gases are ported through the exhaust system.

ABS - ABS stands for Anti-lock Braking System. This utilizes a computerized system to sense wheel lockup and then release and reapply the brakes many times per second. The result is a steady controlled braking without skidding.

Balaclava - A Balaclava is a thin pull-over head and neck cover with eye slits for winter usage under a motorcycle helmet.

Belt drive - Belt Drive is a method to transmit power from the transmission to the rear wheel of the motorcycle using a belt. The belt requires practically no maintenance. Harley-Davidson has used Belt-Drive systems on most of its motorcycles in recent years.

CC - CC refers to the cubic centimeters of displacement of an engine. Usually written, for example, as 1200cc. Total engine displacement is the volume displaced by a piston in a cylinder during a single stroke, multiplied by the number of cylinders.

Dry clutch - A Dry Clutch is more like the clutch found on an automobile that separates the engine from the transmission. There is a dry connection between the engine and transmission.

Wet clutch - A Wet Clutch is one that contains many plates that are in the oil spray of the transmission and the oil gets between the plates. The plates on wet clutches have a tendency to stick together when the bike sits. So, when you start the bike in the morning, before you put it in first gear to move off, depress the clutch lever for about 30 seconds to allow the oil on the plates to drain off and the plates to separate. Otherwise, you'll get a decided clunk and slight movement forward when you put it in first.

DOT helmet rating - The Department of Transportation (DOT) rates motorcycle helmets. The rating is based on dropping the helmet containing a simulated head from a height of 10 feet.

MSF - MSF stands for The Motorcycle Safety Foundation that sponsors motorcycle training courses.
RPM - RPM is defined as Revolutions Per Minute. Horsepower, Torque, and RPM are interrelated by the formula: HP = Torque * RPM/5252.

Soft tail - A Soft Tail is a motorcycle that appears to have a Hard Tail rear suspension but in reality has shock absorbers that are hidden from view. Harley-Davidson has many Soft Tail models but they call them Softails.

T- Bone - A T-Bone is a category of motorcycle accident where the rider runs head-on into the side of another vehicle. Usually, the other vehicle is a car that has turned left in front of the rider and the rider cannot perform an evasive maneuver or swerve to avoid the car and hits it straight on in the side. The car is the top of the "T" and the motorcycle is the vertical part of the "T."

Wind triangle - A triangular cloth or piece of leather worn around the neck area for wind protection.




Harley Davidson Bike: History

Dirt Bikes

The Harley Davidson Culture

Motorcycle safety

Motorcycle glossary