Bold reference numbers in this section identify parts shown in this exploded view diagram. These parts do not appear in the figures near the text.

Remove the pin (7), the bushes (10) and the head gasket (A) from their seats into the cylinder (Section N 4.4, Disassembling the engine heads).

Use tool part no. 88700.5644 to bring horizontal cylinder piston (8) to TDC.

If needed, aid removal by rocking the cylinder gently with both hands or tap cylinder base lightly with a plastic mallet. Lift cylinder just enough to give access to gudgeon pin (3).

Cylinder and piston are best removed together. This will save time on reassembly, as inserting the piston into the cylinder is a delicate, lengthy procedure. The recommended removal procedure is as follows.

Block off the casing opening with a cloth or with soft paper to prevent foreign matters or solid waste from entering the engine block.

Bring the horizontal cylinder piston (8) to top dead center using tool part no. 88700.5644. Repeat operations performed on the vertical cylinder to remove horizontal cylinder-piston assembly.

Check that the inner surface is perfectly smooth. Measure the cylinder bore diameter (D) at three different heights and in two directions at 90° to one another. This makes it possible to obtain the coupling, taper and oval values (see specified values under Sect. C 1.1, Cylinder / piston).

Change the cylinder if damaged or excessively worn. The special silicon carbide coating applied to the inner bore provides excellent friction and wear resistance, but prevents grinding.

Measure piston diameter (P) 10 mm above skirt base, at right angles to the axis of the gudgeon pin.

For clearance values refer to Sect. C 1.1, Cylinder / piston.

They must be perfectly smooth, without signs of scoring, steps or blueish stains due to overheating. The well-lubricated gudgeon pin must slide smoothly inside the piston.

Assembly clearance must be: 0.002-0.008 mm

Max allowed wear limit: 0.035 mm

Top (1st) ring max. wear limit: 0.15 mm
Other rings (2nd ring and scraper ring) wear limit: 0.10 mm

0.025 mm.

It is important that piston ring (A) be perfectly square to cylinder during measurement. To this end, fit the piston (9) without the piston rings into the cylinder and place the piston ring to be measured on top of the piston.

Top ring and second ring (nominal): 0.20 - 0.40 mm

Wear limit: 0.80 mm.

Oil scraper ring (nominal): 0.30 - 0.60 mm

Wear limit: 1.0 mm.

Cylinder class is identified by a letter punched on cylinder top face in the cylinder / head contact surface. Piston class is punched on the piston crown, between the two valve pockets.

If piston and cylinder were separated during disassembly, rotate piston rings so that their open ends are spaced 120 degrees apart. Note that piston ring mark must be facing up (pointing to piston crown).

Lubricate cylinder inner bore with engine oil. Use an all-purpose tool to slide piston gently into cylinder with the smaller valve pocket placed at exhaust end.

Use tool part no. 88700.5644 to bring connecting rod small end to TDC. Slide the cylinder-piston assembly onto the casing stud bolts.

Push connecting rod small end into the piston so as to line up gudgeon pin (3) hole. Lubricate and fit gudgeon pin. Gudgeon pin must slide smoothly inside the con-rod small end bushing and piston (9).

Position the locating pin (7), the head gasket (A) (Sect. N 4.4, Refitting the heads) and the centering bush (10).