VESPA ET4 50 Spécifications télécharger pdf (Page 86)

Choosing the gasket

This engine is manufactured with two different head gasket solutions:

- Fibre gasket drw. 969244 0.95 mm thick.

- Steel gasket drw. 969393 0.3 mm thick.

In order to guarantee an adequate compression ratio, the gaskets match cylinders with different heights:

- Fibre gaskets with cylinder 56.45 mm high

- Fibre gaskets with cylinder 57.15 mm high

In order to carry out the revision both gaskets should be present on the spare parts.

All pin-piston-cylinder units supplied with the spare parts present cylinders 57.15 mm high

- Provisionally fit the piston into the cylinder, without any base gasket.

- Fit a dial gauge on the specific tool, then rest both on a stop surface.

- Zero set the dial gauge on the stop surface. Keeping the zero position, assemble the tool on the cylinder

and lock it with 2 nuts as shown in the figure.

- Rotate the crankshaft until TDC (the inverted point of the dial gauge rotation)

- Measure piston protrusion compared with the head plane and determine the gasket thickness to be

used according to the table below. By correctly identifying the cylinder base gasket thickness, an ade-

quate compression ratio is maintained.

- Remove the specific tool and the cylinder.

Characteristic

Standard compression ratio

C.R. 11.5 ÷ 12 ÷ 1

CYLINDER BASE GASKET THICKNESS

Specification

Desc./Quantity

Cylinder height 56.45 ± 0.05

Head gasket thickness (fibre) 0.95 ± 0.06

Measure detected 0.9 ± 0.05

Base gasket thickness 0.4

Measure detected 1 ± 0.05

Base gasket thickness 0.5

CYLINDER BASE GASKET THICKNESS

Specification

Desc./Quantity

Cylinder height 57.15 ± 0.05

Head gasket thickness (steel) 0.3 ± 0.05

Measure detected 0.20 ± 0.05

Base gasket thickness 0.4

Measure detected 0.30 ± 0.05

Base gasket thickness 0.5

Engine ET4 50

ENG - 86

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VESPA ET4 50 Spécifications Page 86