What Bikes Used to Sound Like
Here is a link to a Honda Website that has nearly all of their early years of racing motorcycle soundbites listed. (Plus lots of others).

For those of you too young to know what a Honda 6 (RC166), sounded like, have a play around and imagine what those machines blasting around the mountain circuit sounded like.

For those of you who can remember them, ooh the nostalgia ……..

http://www.honda.co.jp/hondafan/SoundofHonda/engine/index.html

Here is a photograph of a rod & piston from a 250-6

250-6 Specification

Engine:
Honda six-cylinder, flanked, facing forward, four-stroke, with two-shaft overhead valve distribution, gear-operated, and four valves per cylinder. Displacement 247.2 cc. (39 mm. x 34.5 mm.—250). 

Cooling: Air
Transmission: Seven-speed block
Power: About 60 h.p. at 18,000  
Maximum speed: Over 150 m.p.h. 
Chassis: Double cradle, tubular, open below. Front and rear, telescopic suspension
Brakes: Front and rear, central drum, double cam

Source: What Bikes Used to Sound Like