Polini Evolution 133 cc aluminum cylinder for Vespa PV and PK
With the 133 Evolution, Polini Motori presents a completely new development. The cylinder is made of aluminum with Nikasil coating. With a 57 mm bore and 51 mm stroke, 133 cc displacement is available. The timing is 124° transfer port to 179° exhaust. The layout is determined by six transfer ports. This is a completely new design with a large volume.
The exhaust shape is also new. The outlet is 38 mm wide, which corresponds to 68 % chord dimension. The stud bolt spacing (M8) is 56 mm and there is enough meat for further tuning. The piston comes with two 1.5 mm thin piston rings. It is coated to facilitate the running-in phase. The head is made of cast aluminum with a high silicon content. It also has additional cooling fins on the underside. This significantly improves heat dissipation, both from the cylinder itself and from the head. The compression has also been slightly adjusted and the head is sealed with a copper gasket.
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