PIAGGIO Vespa 150 1962 Operation And Maintenance Manual page 10

Cooling effected at all engine speeds by a centrifugal fan (see Fig. 7).
The muffler is of the expansion and absorption combined type with very high silencing
efficiency.
Air cleaner mounted inside the body. Air goes to the carburetor through a large flexible inlet
tube, a silencing chamber and porous filter, which ensures a very quiet air intake.
We recommend not to alter the muffler or the air cleaner but to keep them in perfect
efficiency, to ensure that the noise level does not exceed the limits prescribed by law.
Fig. 7 - Cooling
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