2006 Harley Davidson

The Heritage Softail

These big-twin motorcycles capitalize on Harley's strong value on tradition. With the rear-wheel suspension hidden under the transmission, they are visually similar to the hardtail" choppers popular in the 1960s and 1970s, as well as from their own earlier history.

In keeping with that tradition, Harley offers Softail models with "Heritage" styling that incorporate design cues from throughout their history.

The classic Harley-Davidson engines are V-twin engines, with a 45° angle between the cylinders. The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.

This 45° angle is covered under several United States patents and is an engineering trade-off that allows a large, high-torque engine in a relatively small space. It causes the cylinders to fire at uneven intervals and produces the choppy "potato-potato" sound so strongly linked to the Harley-Davidson brand.

To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor. This is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark". The exhaust note is basically a throaty growling sound with some popping – the sound of thunder.