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Internal combustion engines produce power by igniting fuel inside of an airtight cylinder and forcing a piston out of the cylinder at high speed. This process can be fueled by a number of substances, but the vast majority of engines use gasoline or diesel fuel. There are four distinct stages in the functioning of an internal combustion engine.

Intake

In the intake step, the piston is drawn down the cylinder while the valve is open. This draws air into the cylinder, where it is mixed with fuel. The piston and the valves are connected through a series of parts in this order: piston, connecting rod, crankshaft, camshaft, lifter and valve. This allows the valve to open and close at precisely the right time in relation to the motion of the piston.

Compression

When the piston reaches the lowest point in its back-and-forth motion, it moves from intake to compression. A protrusion on the rotating camshaft pushes the lifter against the valve, forcing the valve to close. At the same time the piston moves back up the cylinder, compressing the mixture of fuel and air that is now trapped in the cylinder.

Power

When the piston reaches the top of the cylinder and the fuel and air mixture is at maximum pressure, the spark plug creates a spark and the mixture is ignited. Gasoline is a highly explosive fuel, so this event creates a great deal of power. The explosion drives the piston back down the cylinder. Through the connections mentioned above, this movement is translated from linear to circular motion and transferred to the transmission of the vehicle, where it moves an axle that is attached to wheels, powering the vehicle.

Exhaust

As soon as the piston reaches the bottom of the cylinder, the valve opens, the piston goes back up the cylinder and the exhaust from the ignited fuel is forced out of the cylinder. The cycle then begins again. All of this happens with great frequency, creating an even flow of power to the wheels of the vehicle.

S&S Cycles in Wisconsin makes carburetors, performance parts and entire V-Twin engine assemblies for Harley-Davidson and Harley-Davidson-like motorcycles like Big Dog and Ironhorse motorcycles. The engines cost about as much as Harley engines, but they are hand assembled, come with large displacements and have a long-established reputation for craftsmanship. Several very visible marks make them easy to recognize. S&S motors also have unique engine identification numbers which, because S&S manufactures fewer engines, are shorter than Harley engine identification numbers.

Instructions

1

Walk to the right side of the engine and look at the carburetor. S&S engines come equipped with S&S carburetors. These carburetors have a distinctive, polished-steel, tear-drop-shaped air cover that is stamped with "S&S."

2

Look at the cylinder heads. S&S engines come with cylinder heads stamped "S&S " on the right side of the engine. "S&S" is also stamped on the right side of the transmission cover.

3

Illuminate the left side of the motor with a flashlight and examine the federally mandated engine number on the left side of the crankcase at the base of the rear cylinder. Harley-Davidson engines have engine numbers comprised of four letters followed by six numbers. All S&S motors have seven- or eight-character engine codes that begin and end with an asterisk. A typical S&S engine code begins, after the asterisk, with a single letter followed by five digits.