buell s1 lightning '97 マニュアル

See 

 The transmission is a five-speed constant-

mesh type housed in an extension of the crankcase. The
transmission permits the rider to vary the ratio of engine
speed-to-rear driving wheel speed in order to meet the vary-
ing conditions of operation.

The transmission is foot-operated by the gear shifter lever,
which transmits the force through a gear shifter shaft. The
shifter shaft actuates a pawl and a shifter fork drum. The
shifter fork drum moves shifter forks, which slide a series of
shifter clutch gears, on the mainshaft and countershaft, into
and out of mesh with the other gears.

Drain transmission and refill to correct level with fresh, clean
lubricant at least once each year or every 5000 miles (8000
km), whichever comes first. For best results, drain lubricant
while hot. 

See 

in Section 1 for more

information.