BSA Winged Wheel W1 Instruction Manual page 26

TABLE II.
RECOMMENDED DECARBONISATXON A
PERIODS.
I fem. Decavbonisa :W'y
Exhaust Port 1.000 . 1.200 miles.
Silencer Examine at same
time as exhaust
port, and decarbou-
ise if necessary.
Cylinder Head and Piston 2,000 — 2,400 miles.
Exhaust Port.
Accumulated carbon in the exhaust port (11:. in
the cylinder aperture), and also in the first inch or
two of the pipe. is the most prolific cause of power
loss, because it has the effect of reducing the area
of the orifice through which the exhaust gas has to
pass on its way out of the cylinder, and it therefore
offers increased back pressure.
Fig. 10. View into port with pipe 05 and silencer
dismantled.
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