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TRANSMISSION:
A. Construction and Operation (Fig. 67)
BS 50 60 Sport 90 cc
Transmission Mechanism in Neutral Gear Position.
The transmission in the rotary valve engines is of a constant mesh, rotary type, running in oil. In the 50, 60
Sport and 90 cc engines, the transmission is 4-speed. The 175 Dual Twin has a transmission which is both
rotary change type 4-speed and a return change type 5-speed, made active by a simple flip of a lever.
The transmission consists of two shafts: the countershaft (or clutch shaft) and the drive shaft. The gears on
the countershaft are referred to with the suffix letter "A", for example, "first gear A." The gears on the drive
shaft are referred to with the suffix letter "B", for example, "first gear B."
First gear A is a part of the countershaft. Second gear A slides on the splined portion of the countershaft.
Third gear A and fourth gear A rotate freely on the countershaft. These three spinning gears transmit
power when they are engaged by drive dogs on the gears next to them. (Fifth gear A on 175 DT is keyed to
the shaft.)
Fourth gear B and third gear B are fitted to the splined portion of the drive shaft and turn with the drive
shaft. Second gear B, first gear B (and fifth gear B on 175 DT) turn freely on the drive shaft. Third gear B
slides from side to side on the splined portion of the drive shaft and engages either first gear B or second
gear B by means of the drive dogs on the sides of the gear.
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