Part 1 - Reference Section

Reference Section

Piaggio Hyper 2 50cc Engine

This includes both Liquid Cooled (known as LC) and Air Cooled (AC) varieties. This is just a reference section so you can check on dimensions, diameters, clearances, that sort of thing. Don’t panic if you don’t know what a ‘connecting rod small end OD’ is, these things will be explained later on.

Specifications – 50cc AC/LC OEM

	50cc Air Cooled (AC)	50cc Liquid Cooled (LC)
Engine cycle	2 Stroke petrol
Displacement (CC)	49.4 cubic centimetres
Bore (cylinder diameter)	40.0 mm
Stroke (TDC-BDC)	39.3 mm
Cooling system	Forced air	Liquid
Ignition	Electronic Capacitive Discharge (CDI)
Fuel feed	Multi jet carburettor with automatic choke
Oil system	Separate driven oil delivery system
Transmission	Torque controlled Continuous Variable Transmission
	3 axis gearbox
	Centrifugal dry clutch
Starting system	Electric motor and kick-start
Engine weight	25 kgs
Emissions compliance	EURO 2

 

Above is a table of the basics, not really any good to anyone but it’s in here anyway. Next thing to cover is bikes fitted with the Piaggio Hyper 2 and they are broken down as follows;

PIAGGIO 50cc AIR COOLED ENGINE

Gilera	ICE, SKP 50 (STALKER), STORM
Italjet	JETSET, TORPEDO 50 - 2002 onwards
Piaggio	DIESIS, NRG EXTREME, NRG Mc3, FREE, LIBERTY, SFERA, VESPA ET2, LX50, FLY 50, ZIP 50

PIAGGIO 50cc LIQUID COOLED ENGINES

Gilera	DNA 50, RUNNER 50
Piaggio	NRG Mc2, NRG EXTREME, NRG Mc3, QUARTZ, ZIP SP
Aprilia	SR 50 LC 2004
Derbi	GP1

Blog Layout

The layout of this blog is universal. The diagrams and drawing have been designed to be easy to read and clear to understand. Below is an example, showing a 50cc water cooled transmission casing. The bolts required have been given as the ISO thread size. Also shown is what torque should be applied to the bolt in question. For simplicity if one bolt is marked as M6 (as shown below) and is accompanied by a torque value (in this instance 12Nm) any other M6 bolt displayed also requires a 12Nm torque value. This cuts down on the complexity of the drawing/diagram. Also shown in the example below is a measurement, which will always be in millimetres (mm). The type of fitting is also displayed, in this case a Hex Head bolt.

Some diagrams/drawings will be of plan design, simply because it’s easier to understand. Also some parts will be abbreviated to reduce complications. All abbreviations will be listed with each diagram/drawing. I hate legends and keys that are at the back of books! The example below shows a cross-section of a crankcase, DW signifies where the alignment dowels are located. This diagram also states the orientation to cut down on confusion.

Some other diagrams/drawings are 3D. This is because that’s how you see things. This gives you a better understanding of what you’re looking at and where something should go.

Engine Layout

The Piaggio Hyper II engine has 3 major components, the CYLINDER, the TRANSMISSION and the CASING. Each section has been broken down below and a brief description has been added to make sense of it all.

 

The CYLINDER houses the piston assembly, cylinder, head, combustions chamber, water jacket and thermostat (on water cooled systems), spark plug, and cooling fins (on air cooled systems). Basically this is where the power is produced.

The TRANSMISSION comprises of components that transfer that power to the rear wheel, it also contains the parts that allow a moped/scooter to apply power when required in the form of an automatic clutch. The transmission basically comprises of the variator assembly, front pulley, drive belt, clutch assembly, gear box and rear axle.

The CASING in simple terms is the body which things work in, are fixed to and are held together by. The casing also contributes to the production of power. It has areas more than actual parts which include the crankcase, gearbox (the actual ‘box’ that houses the gears), the main channel (which connects the crankcase to the gearbox) and some other extremities that have other function and will be covered later on.  

First we’re gonna start with the ‘power’ section of the engine. This is the 2 stroke combustion section of the engine which is similar to any 2 stroke petrol engine found on motorcycles, lawnmowers and in rare cases some cars.