NZ motorbike stamps, 1986

 
The Post Office's accompanying blurb at the time:-

The early motor bicycles were commonly referred to as 'motor assisted bicycles', and in effect, that is what they were.  Pedal power was required to get them started, until the engine could take over.  Through research and a lot of trial and error, a successful 2-wheeled motorcycle was eventually produced; one that offered safe, fast, healthy and personal transport. Modern riders, influenced by the latest models from overseas, would not hesitate to describe these early motorcycles as museum pieces.  Yet, by their sturdiness in coping with rough conditions, and the years of reliable and pleasurable service they gave to their owners, these machines have earned a high ranking in the annals of this country's early transport.  The motorcycles shown on the four stamps of this issue are indeed a far cry from the sleekly-designed sophisticated machines we see on today's roads.
1920 1000cc Indian Power Plus (35c stamp)
A typical, big, rugged American motorcycle built for long-distance running over arduous roads,  Popularly known as the 'spring frame' Indian, it was one of the first motorcycles to have a sprung rear wheel.  Many were supplied to the police and military forces.
1927 500cc Norton (45c)
With major racing successes in the Isle of Man, this reliable British motorcycle earned great fame in the racing and sports world.
1930 500cc BSA (60c)
Made by the "Birmingham Small Arms" Company and bearing the logo of three rifles stacked in a pyramid.  This was later changed to emphasise the letters BSA.  One of their most popular models was the 1930 BSA 'Sloper'.
1915 550cc Triumph (75c)
In World War I, the Triumph was exclusively used by British Army dispatch-riders, earning the nickname the 'trusty' Triumph.  Thirty thousand of these machines were supplied to the British and Allied armies.