Cylinder head -POLINI 207 / 210 / 221 cc alloy- Vespa P200, Rally200

Preview: Cylinder head -POLINI 207 / 210 / 221 cc alloy- Vespa P200, Rally200

Description

The Polini cylinder head is the only head with cooling fins on the bottom side. It is supplied with the Polini 210cc and 221cc cylinders. According to Polini it can also be used on the 207cc cast iron cylinder.

compression
The compression is controlled by the different heights of the cylinders and therefore by the height of the squeezing edge. The Polini 221cc cylinder, designed for a 3mm longer crankshaft stroke, is much longer than would be necessary for the pure stroke compensation (1,5mm). Therefore the same cylinder head can be used here without the compression being too high. With the resulting large squish edge of 2.2mm the head has a healthy compression ratio of 9.6:1 even on the larger 221cc cylinder.

Effective compression
Due to the short exhaust control angle of the Polini cylinders, the compression without the value of the stroke in which the exhaust is open is still 6.3:1 even on the 221cc version.

Fits Polini 207cc, Polini 210cc, Polini 221cc for Vespa PX200, Cosa200, Rally200
compression Polini 221ccm: 9,6:1 (2,2mm squish)
spark plug thread: as std. PX200 (long thread, Bosch "CC" or NGK "ES")
Combustion chamber volume with 2,2mm squeezing edge: 25,6ccm
With centering holes for Polini 210cc / 221cc cylinders (centering by pins)

Tuning
Who wants to make the Polini more sporty and give it higher head angles (z.(e.g. with a 1,5mm foot spacer) and/or an exhaust treatment, you can reduce the squish edge (turn off cylinder head or cylinder) to keep the effective compression sufficiently high. With a squish edge reduced by 1mm (1.2mm), the Polini cylinder head on the 221cc Polini cylinder has a compression ratio of 11:1 (effective compression at 180° exhaust angle 6.7:1)

Note: The cylinder head is made for the Polini piston crown radius. If the head is used on a cylinder with Malossi piston, the result is a strongly opening pinch edge angle. This reduces the effectiveness of the pinch edge and therefore the performance. Therefore the head should be reworked in combination with a Malossi piston (piston top angle of the Malossi piston is 14°). The stud bolt holes are cast conically to the combustion chamber opening. Diameter at the sealing surface Ø10mm. The squeezing surface ends without a step in the sealing surface, i.e. the combustion chamber is not screwed in/collapsed.

(US)

OEM numbers (for comparison purposes only)
Polini	2110014, P211.0014, 211.0014, P2110014

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