Mechanical glossary
Motorcycle Operation

Mechanical glossary

A small glossary of ideal mechanics

Have you ever heard of a cylinder, breathing apparatus, flat-plate twin engine or transmission chain? Kezako? If this is your first reaction, then this article is for you.

The bikers' den is undoubtedly the place where the most experienced mechanics meet and exchange secret information about the bowels of their motorcycle in an unknown language. For beginners looking to make a small space for themselves and play handyman apprentices, it's time.

First of all, you need to understand the basic technical vocabulary related to motorcycle mechanics. There is no need to refer to the magic formula or buy the book "Mechanics for Dummies" for this, you need a simple resume.

Motorcycle mechanics dictionary in alphabetical order

A - B - C - D - E - F - G - H - I - J - K - L - M - NO - P - Q - R - S - T - U - V - W - X - Y - Z

А

ABS: Anti-lock braking system - This system prevents the wheels from locking during braking and thus controls your motorcycle.

Прием: The first cycle of the engine, during which air and gasoline are drawn into the cylinder after the vacuum created by the action of the piston.

Cylinder bore: Bore of the cylinder. Reforming allows you to correct the shape of the cylinders, made oval, through wear.

Cooling fins: On an air-cooled engine, the cylinders are covered with fins that increase the thermal contact surface and provide better heat dissipation.

Ignition: Inflammation of the air / gasoline mixture due to the spark plug located in the cylinder head.

Shock absorber: a device to cushion and cushion shocks and vibrations, and to keep the wheel in contact with the ground. This is most often the case with a rear suspension spring / shock absorber combination.

Power steering: The steering damper prevents the steering wheel from coming in. It is often fitted as standard on sport bikes that feature rigid frames and suspensions.

camshaft: device for activating and synchronizing the opening of valves.

Head camshaft (ACT): Architecture in which the camshaft is located in the cylinder head. It is also called SOHC for single outboard camshaft. The Dual Overhead Camshaft (DOHC) consists of an ACT that controls the intake valves and an ACT that controls the exhaust valves.

Plate: This term refers to the horizontal position of the motorcycle. The horizontally trimmed car offers greater stability, while the forward leaning ratio allows for a sportier ride.

Self-ignition: An abnormal occurrence of a spark ignition engine cycle (2 or 4 strikes) during which ignition occurs due to excessive temperature during compression or hot spots (eg calamine).

Б

Scanning: Phase of the engine cycle during which fresh gases emit flue gases into the exhaust gases. Long scan times favor high rpms, but result in a loss of torque at the bottom of the circle.

Tread: The center of the tire rubber is in direct contact with the road. It is on this strip that water evacuation sculptures and wear indicators are located.

Two-cylinder: An engine consisting of two cylinders, of which several architectures exist. The two-cylinder is characterized by its "character" and availability at low to medium revs, but generally lacks flexibility.

Connecting rod: a piece consisting of two joints connecting the pistons to the crankshaft. This allows the straight back and forward pistons to be transformed into a continuous circular motion of the crankshaft.

Bushel: On carburetor engines. This cylindrical or flat part (guillotine), controlled by a gas cable, determines the passage of air through the carburetor.

Spark plug: It is an electrical element that ignites the air / gasoline mixture in the combustion chamber of a spark ignition engine. It is not available on a compression ignition engine (Diesel).

Boxer: the pistons of a boxing engine move like boxers in the ring when one moves forward and the other back, so that the pmh of one corresponds to the pmb of the other. The two connecting rods are on the same crank arm. So with the motor angle, we have a 180 degree setting. But today we no longer do too much of this nuance and talk about boxing even at BMW.

Oscillating arm: the part of the articulated frame that provides the rear suspension in addition to the spring / damper combination. This part can consist of an arm (mono arm) or two arms connecting the rear wheel to the frame.

Injection nozzle: The nozzle is a calibrated orifice through which gasoline, oil or air flows.

Stop: Part for limiting the range of motion of another mechanical element.

С

Frame: This is the skeleton of a motorcycle. The frame allows for the connection between the various elements of the machine. The cradle frame consists of a tube connecting the swing arm to the steering column, said to be a double cradle when split under the engine. The tubular mesh is made up of several tubes that form triangles and provide high rigidity. The perimeter frame surrounds the engine with two rarefied ones. The beam frame consists only of a large tube connecting the swing arm and steering column. Finally, the open frame, mostly used on a scooter, has no top tube.

Calamine: This is the carbon residue deposited at the top of the piston and in the combustion chamber of the engine.

Carburetor: This member makes a mixture of air and gasoline according to a specific richness to ensure optimal combustion. On recent motorcycles, power comes primarily from injection systems.

Gimbal: An articulated transmission system that connects two shafts or uneven axles to provide torque transmission during suspension travel.

Chassis: The housing is the outer part that protects the mechanical element and connects the moving parts of the engine. It also includes the lubrication elements required for the organ to function. The hull is said to be dry when the lubrication system is separated from the engine block.

Distribution chain: This chain (or belt) connects the crankshaft to the camshafts, which then operate the valves

Transmission chain: This chain, often an O-ring, transfers power from the transmission to the rear wheel. This requires more maintenance than other transmission systems, including the gimbal or belt, with the recommended lubrication every 500 km.

Inner tube: A rubber flange that stores air between the rim and tire. Today, most motorcycle tires are referred to as "tubeless" tires and no longer require an inner tube. On the other hand, they are very present in XC and Enduro.

The combustion chamber: the area between the top of the piston and the cylinder head where the air / gasoline mixture enters the combustion.

Hunting: distance, in mm, separating the extension of the steering column from the ground and the vertical distance through the front wheel axle. The more you hunt, the more stable the bike, but the less maneuverable it is.

Horses: Powertrains that relate horse power to engine strength (CH). Can also be expressed in kW, according to the calculation rule 1 kW = 1341 horsepower (horsepower) or 1 kW = 1 15962 horsepower (metric steam horse), not to be confused with the fiscal power of the engine used to calculate vehicle registration tax funds expressed in Tax Horses (CV).

Compression (engine): The phase in the engine cycle where the air / gasoline mixture is compressed by the piston to facilitate ignition.

Compression (suspension): This term refers to the compression damping effect of the suspension.

Traction control system: Driving assistance system prevents loss of traction in case of excessive acceleration. Each manufacturer has developed its own technology, and the names are several DTCs for Ducati and BMW, ATC for Aprilia or S-KTRC for Kawasaki.

Torque: Measuring the rotating force in meters per kilogram (µg) or deca Newton (Nm) using the formula 1µg = Nm / 0 981. Multiply the torque in µg by the RPM and then divide by 716 to get the power.

Belt: The belt plays the same role as the transmission chain, but has a longer life and requires less maintenance.

Race (engine): This is the distance traveled by the piston between high and low dead spots.

Race (suspensions): Dead race refers to the sinking value of the suspensions after the motorcycle is placed on the wheels. This allows you to maintain contact with the road during the transfer of the load.

A rewarding trip refers to the travel available after the race dies and the driver's sinking is removed.

Intersection: Refers to the timing of the simultaneous opening of the intake and exhaust valves.

Cylinder head: The cylinder head is the top of the cylinder where compression and ignition takes place. Above the 4-stroke engine, its lights (holes), blocked by valves, allow the flow of an air-gasoline mixture and the evacuation of flue gases.

Rocker: connects the camshaft to the valves to open it.

Storage tank: The part of the carburetor containing the fuel reserve

Cylinder: This is the engine element in which the piston moves. Its hole and stroke allow you to determine its offset.

Cylinder offset: determined by cylinder bore and piston stroke, displacement corresponds to the volume displaced by the action of the pistons.

CX: Air drag coefficient indicating air drag.

CZ: Air lift ratio, indicating the change in the loads on the front and rear wheels as a function of speed. On the plane Cz is positive (takeoff), in Formula 1 it is negative (support).

Д

Deviation: Refers to the maximum duration of travel of the shock absorber or fork between expansion and compression stops.

Gear: The transmission allows the engine speed to be adapted to the speed of the motorcycle. Thus, depending on the choice of the gear ratio, acceleration and recovery or top speed can be promoted.

Relaxation: Relaxation refers to the rebound effect of the suspension, it is the opposite of compression

Diagonal: A tire structure in which sheets with diagonal fibers are applied perpendicular to each other to provide a higher load-bearing capacity. This design only provides low side grip and heats up quickly.

Brake disk: hard on the wheel, the brake disc is slowed down by the pads during braking and thus makes the wheel stop.

Distribution: The distribution includes mechanisms for the intake of an air-gasoline mixture and the exhaust of gases into the cylinder.

Drip (Chattering): This is a phenomenon of wheel bouncing on the ground that results in loss of grip and can be caused by poor suspension adjustment, poor weight distribution, or insufficient tire pressure.

Hard (or hose): This registered name refers to a fitting, originally made of rubber, which allows the various organs of the motorcycle to be connected and fluid to be transferred to the motorcycle, providing protection from external aggressions.

Е

Exhaust: The last phase of the engine cycle, when the burnt gases escape, is often used to refer to the pot or muffler itself.

Wheelbase: Refers to the distance between the front wheel and the rear wheel axles

Support Service: The system consists of one or more movable pistons that push the brake pads against the disc to brake the motorcycle.

Thread: the thread corresponds to the pitch of the screw. It is a network formed on a cylindrical surface.

Air filter: Air filter stops unwanted particles before air enters the engine. The presence of these particles in the cylinder leads to premature wear. Inhibit (colmatized) it prevents breathing of the engine, causing consumption and reduced performance. Therefore, it is necessary to regularly check the condition of its filter.

Flat twin: Typical BMW Motorrad engine architecture. It is a double cylinder where two cylinders are positioned exactly opposite each other on either side of the crankshaft.

Brake: The brake is a device that controls the stopping of the motorcycle. It consists of either drums, one or two brake discs, and as many calipers and pads as possible.

Friction: Friction refers to the friction generated by the mechanism.

Fork: The telescopic fork is the front suspension of the motorcycle. It is said to be inverted when the shells are positioned over the pipes. In this configuration, it provides more rigidity to the front of the bike.

shell: The shells form the fixed part of the fork in which the tubes slide.

Г

Мanagement: This is a sudden directional movement that occurs when accelerating and is triggered after a road violation. Steering flaps avoid or restrict steering wheels.

Н

я

Injection: Injection allows the engine to accurately deliver fuel either into the intake port (indirect injection) or directly into the combustion chamber (direct injection, not yet used in motorcycles). It is accompanied by an electronic computer that optimally manages the power supply.

J.

Rim: This is the part of the wheel that the tire rests on. He can talk or stick. The rims can accommodate inner tubes, especially in the case of spokes. When tubeless tires are used, they must offer a perfect seal.

Spinnaker seal: This is a radial seal ring that allows the moving shaft to rotate and slide. On the fork, it keeps the oil in the sheath as the pipes slide. Spi is a registered trademark, we usually talk about lip seal (s)

Skirt: this is the part that guides the piston in the cylinder. In a two-stroke engine, the skirt allows the light to open and close. The role is provided by the camshaft and valves in a four-stroke engine.

К

kW: power of one motor in joule per second

Л

tongue: The most efficient camshaft valve control system.

Luvuament: Converts to motorcycle ripple at high speed, which then touches the steering, but in a less important way than the steering wheel. The origins are numerous and may be from a tire pressure problem, poor wheel alignment, an oscillating arm problem, or a change in aerodynamics caused by a bubble, passenger, or suitcases.

М

Master cylinder: The room is equipped with a sliding piston that transmits the pressure of the hydraulic fluid to control the brakes or clutch. This part is connected to the reservoir containing the hydraulic fluid.

Manetho: This is the crankshaft that is connected to the connecting rod.

Single cylinder: Single cylinder engine has only one cylinder.

Two-stroke engine: refers to an internal combustion engine whose duty cycle occurs in one stroke.

Four-stroke engine: means an internal combustion engine whose cycle works as follows: intake, compression, combustion / relaxation and exhaust gases

Stupica: Refers to the center axis of the wheel.

Н

О

П

Star: A pinion is a toothed disc that allows the transmission of rotational force by means of a gear train.

Piston: The piston is the part of the engine that goes back and forth in the cylinder and compresses the mixture of air and gasoline.

Brake pads: brake organ, brake pads are built into the caliper and tighten the disc to brake the wheel.

Tray: A piece of clutch pushes the disc against the flywheel or clutch nut.

Low neutral / high neutral point: High dead center defines the highest point reached by the piston stroke, low neutral refers to the lowest.

Preload: Also called prestressing, it refers to the initial compression of the suspension spring. By increasing it, the dead blow decreases and the initial force increases, but the stiffness of the suspension remains the same because it is determined by the spring itself.

Question

Р

Radial: The radial structure of the tire is made up of perpendicular layers. This carcass is lighter in weight than the diagonal carcass, which requires more sheets and thus creates better maneuverability. Another advantage of this design is that it does not transfer lateral bending to the tread.

Radiator: The radiator allows the coolant (oil or water) to cool. It consists of cooling tubes and fins that dissipate heat.

Volume ratio: also called compression ratio, it is the ratio between the capacity of a cylinder when the piston is at the low neutral level and the volume of the combustion chamber.

bug: Abnormal engine noise

Breather: The breather refers to the channel that allows the evacuation of the engine by the condensation phenomenon of oil or water vapor.

Wealth: the richness of the mixture of air and gasoline corresponds to the proportion of fuel contained in the air at the time of carburizing.

Rotor: It is a moving part of an electrical system that rotates inside the stator.

С

Hoof motor: The motor hoof is the cover that covers or protects the cartwheels. On road bikes, this is mostly a piece of clothing. The hoof can also take the form of a protective metal plate on off-road bikes and trails.

Segment: Rings surrounding the piston in the grooves to seal and evacuate calories from the piston to the cylinder wall

Brake: An automatic braking system connected to the master cylinder that uses the engine's intake vacuum to increase the force required to apply the brakes.

Shimmy: Problem causing steering oscillation during deceleration at low speed. Unlike the handlebars, the pad is not caused by an external problem, but by an anomaly in the motorcycle that can arise from balancing, steering adjustments, tires ...

Silencers: placed at the end of the exhaust line, the muffler aims to reduce the noise caused by the exhaust gases.

Valve: A valve is a valve used to open or close an intake or exhaust port.

Star: Enrichment system for easy cold starting.

Stator: It is a fixed part of an electrical system, such as a generator, that houses a rotating rotor.

Т

Drum: The brake drums consist of a bell and jaws with linings that move apart to rub the inside of the drum and brake the wheel. Low resistance to heat and heavier disc systems, drums have now virtually disappeared from modern motorcycles.

Compression ratio: see volumetric ratio

Transmission: Gearbox refers to the entire mechanical device for transmitting the rotational motion of the crankshaft to the rear wheel of a motorcycle.

Tubeless: This English name means "without inner tube".

У

V

V-Twin: Twin-cylinder engine architecture. The V-twin, indispensable from the manufacturer Harley-Davidson, consists of 2 cylinders separated by an angle. When the angle is 90 °, we are also talking about an L-shaped twin cylinder (Ducati). It is characterized by its sound.

Crankshaft: The crankshaft converts the forward and backward motion of the piston into a continuous rotating motion thanks to the connecting rod. It then transfers this pivot mechanism to other mechanical components of the motorcycle, such as the transmission.

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