Polini has reworked the legendary 133 very gently. More was not necessary with the very sophisticated cylinder. The essential innovation concerns the cylinder head.
The bore of 57 mm has been kept and so with 51 cc shaft 130 cc and with 54 shaft 138 cc are available. The layout of the cylinder is unchanged and is determined by the six transfer ports.
The piston is made of die-cast, which gives it a very good durability at low weight.
The new head is made of cast aluminium with a high silicon content. It also has additional cooling fins on the bottom. This means that the heat is dissipated much better, both from the cylinder itself and from the head. The compression has also been slightly modified.
The new copper gasket not only conducts heat better, it also contributes to a significantly better seal between the cylinder and head.
Conclusion:Classics made even better!
Spark plug: long thread, e.g. NGK B9ES or Bosch W2CC
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