Acronyms, Terms and Definitions 


ABS Anti-lock Braking System
APRC Aprilia Performance Ride Control
ASC Automatic Stability Control

Bore and Stroke

Relationship between the diameter of a cylinder and the length the piston travels

Brake Calipers Fixed and Floating Calipers
Camshaft Single or Double Overhead Camshaft (SOHC or DOHC), Pushrod
Carburetor Blends air and fuel for an internal combustion engine.
Catalytic Converter Converts harmful emissions to harmless compounds
CDI Capacitor discharge ignition
Cellasto Microcellular polyurethane elastomers that enhance driving comfort
Clutch Multi-plate, wet, dry
Compression Ratio Ratio of the volume of a combustion chamber from its largest capacity to its smallest capacity
Counter Steering "Steer left to turn right"
Crankshaft Transforms the energy from the pistons (lineary) into a rotary motion
CVT Continuous Variable Transmission
Desmodromic Valve A reciprocating engine valve that is positively closed by a cam and leverage system
Disc Brakes Difference between fixed and floating disc brakes
DOHC Double Overhead Camshaft
Drum brakes Single or twin leading shoe
DSS Ducati Skyhook System
ECU Electronic Control Unit
EFI Electronic Fuel Injection
ESA Electronic Suspension Adjustment
EXUP Exhaust Ultimate Power Valve
Floating Sprocket To help keep the sprocket properly aligned
Four Stroke Engine Most popular modern motorcycle engines
Gear Ratios Explaining the relationship between various components and how it impacts on power delivery
GVWR Gross Vehicle Weight Ratio
High Side Losing control as a result of extraordinary power added to the rear wheel
Hub-center steering An alternative front-end steering/suspension system
Knucklehead Engine Harley-Davidson motorcycle engine
Leading shoe Drum brake - single or twin leading shoe
Multi-plate clutch The most common motorcycle clutch
Paralever Eliminating "jacking" in a shaft driven bike
PCM Powertrain Control Module
Power and Torque Both are needed to get your bike moving.  But what is it?
Pushrod Camshaft located inside the engine rather than in the head and driven by pushrods
Rake The angle between the neck a bike and a vertical line
Ram Air Increasing engine power through the use of airflow
Reed Valve A valve opening under vacuum to allow fuel/air mixture to enter the crank of a 2-stroke
Ride by Wire The use of electrical or electro-mechanical systems for performing vehicle functions traditionally achieved by mechanical linkages/acruatiors
Seamless Gearbox Also referred to as seamless shifting, seamless transmission or Zeroshift transmission
Shock Absorbers Single tube, double tube, front, rear
Slipper clutch  
SOHC Single Overhead Camshaft
Steering Damper Inhibits undesirable movement of the steering mechanism.
Supercharging How these forced air induction systems work and why they are the way of the future.
Sump Wet and dry sump
Suspension adjustment Also covering both front and rear suspension rebound and compression settings
Swingarm The main component of the rear suspension to hold the rear axle firmly, pivot vertically, allowing the suspension to do its work.
Tank Slapper An unwanted, quick and scary oscillation of the front wheel
Telelever A BMW patented front suspension system
Torque Refers to force - read power and torque
Traction Control Designed to prevent loss of traction of road driven wheels
Trail The distance between tyre surface contact and a vertical line from the axis to the surface
Triple Tree Central to the steering mechanism of a bike
Turbocharger Boosting an engine without significantly increasing weight
Two Stroke Engine Mainly used on smaller bikes, such as 50 cc.  Reducing in popularity due to pollution
VTEC Variable Valve Timing and Lift Electronic Control
Wheels A discussion on spoke and alloy wheels
YPVS Yamaha Power Valve System

We are systematically expanding this section on acronyms, terms and definitions.  We aim to make it reader friendly and minimise confusing technical jargon.

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