The new Polini BIG EVOLUTION cylinder kits for scooters equipped with Minarelli and Piaggio engines are available is three different sizes:
-One with bore: 47,6mm - stroke:39,3mm - displacement: 70cc
-One with bore: 52mm - stroke:39,3mm - displacement: 84cc
-One with bore: 52mm - stroke:44mm - displacement: 94cc

The aluminium cylinder, with closed-deck cooling system, features a specific working, which increases the thermal stability of the cylinder, cutting the risk of barrel distortion even at the highest temperature. The cylinder liner has a nickel -chrome coating. The head plane is brand new and innovative compared to the ones already present on the market: it features a nickel coating to avoid the detonation problems and then worked on with known process in advanced productive CNC centres that grind it with a centesimal calibration. In this way the head plane is perfectly coupled to the cylinder improving the combustion phase in the burning chamber and increasing the head and cylinder’s life It has 5 transfer ports plus an exhaust port with central bridge to optimise the gas scavenging The distribution diagram is brand new for its performance features. The piston is gravity die-cast in light alloy at high silicon content with a chromed, grinded, and lapped cast iron ring. The head is gravity die-cast from a block and later thermal treated to harden the material the same as for the cylinder: the mechanical resistance can be compared to a head machined from a block.

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