Bold reference numbers in this section identify parts not shown in the figures alongside the text, but which can be found in the exploded view diagram.

Using the tool code 88713.2676, undo the nuts (21) on the cylinder head stud bolts.

Remove the half rings (6) from the valves with a magnetic screwdriver. Extract the closing shims (7) from the valve using a pair of pliers.

Using the claw of the rocker arm spring tensioning kit 88713.2069 installed between the spring and the inner wall of the cylinder head, move the straight end of the rocker arm return spring (19) and (18) and insert it in the drilled shaft.

Carry out the same operation to remove the closing rocker arms (4) and (16), the springs (24) and (25) with the spacers (23).

Check that the cylinder barrel mating surfaces of the cylinder head are free of carbon deposits and scale. If this is not the case, spread diamond dressing compound (6 to 12 micron thickness) on a reference surface and slide the cylinder head on the surface as shown in the figure until a flat finish is obtained.

If the valve seats are excessively damaged, fit oversize seats. Replacement seats are available with 0.03 and 0.06 mm oversized outside diameters.

Check the diameter of head bores and choose the oversized valve seat that will give an interference fit of 0.04 to 0.10 mm.

Heat the cylinder head gradually and evenly up to 150 °C and chill the new valve seats in dry ice.

Drive the seats perfectly square into the head bores using the appropriate valve guide seat installer 88713.2846 and 88713.2847.

CA = Ø 41.6 ± 0.025 mm.

CS = Ø 33.6±0.025 mm.

S = 1.2 mm.

D = 0.2 to 0.4 mm.

Thoroughly check the dimensions of the inner surface of the valve guide. Measure the inside diameter with a bore diameter gauge.

highest measured value – lowest measured value = 0.03 to 0.045 mm;

the maximum permissible wear limit is 0.08 mm.

change the valve guides when the ovality exceeds permissible limit or the clearance to the valve stem is outside the tolerance range;

Valve guides as spare parts are available with outside diameter oversized by 0.03, 0.06 and 0.09 mm.

A= 22.4±0.15 mm.

B= 28.45±0.15 mm.

Service limit: 0.053 mm.

Check the valve stem for buckling. Place valve on a "V" block, set a dial gauge perpendicular to head and measure run-out of valve face at 45°.

Use Prussian blue or a mixture of minimum and oil to check that the contact surface (W) between the valve and seat is 1.4 to 1.6 mm (1.05 to 1.35 mm when new). Grind the seat if the dimension measured is greater than the above limit.

After grinding the seats it is important to check the seal between the valve face and the seat: if the seat contact area (S) on the valve is wider than the 45° band (W) this could lead to poor sealing.

Assembly clearance: 0.025 to 0.049 mm.

Wear limit: 0.08 mm.

Position the cylinder head on the appropriate support 88713.2103.

Use engine oil to lubricate the valve guides sealing rings (8) and insert them from the spring side onto tool 88713.2442.

The closing rocker arm shafts are 10 mm in diameter, whereas the opening rocker arm shafts are 9 mm in diameter.

Load the springs (18) and (19) on the closing rocker arms (16) and (4) respectively using the tool 88713.2069.

Proceed to install the closing rocker arms (4) and (16), the springs (24) and (25), the relative pins on the exhaust side in the same manner as described for the intake side.

Hold the closing rocker arm (16) pushed downwards and fit the closing shim (7) on the valve stem up to reach the rocker arm. If using the old cylinder head, start by fitting the original shim.

Insert the new half rings (6) in the valve groove (T) and release the rocker arm to obtain shim (7) internal position. Turn the closing rocker arm (16), and compress the spring as much as possible while holding the valve, the shim and the half rings in the valve closed position. Release the rocker arm with a rapid motion, so that the half rings seat in the shim.

Repeat the procedure with the opposite valve and check that the top of the valve stem is aligned with the surface of the shim (7); if it is not, repeat the half ring installation procedure.

Refit the timing shafts (Sect. 9 - 4.4, Refitting the camshafts) to check the valve clearance when closed (Sect. 9 - 4.1, Checking and adjusting the valve clearances).

Using an M6 screw, position the opening rocker arm shaft (2) (diameter 9 mm).

Refit the timing shafts (Sect. 9 - 4.4, Refitting the camshafts) to check the valve clearance when open (Sect. 9 - 4.1, Checking and adjusting the valve clearances).

Apply prescribed threadlocker on the plug threads (12): apply the product on the first two plug threads, spreading it for the half circumference (about 180°).

Tighten the plugs to a torque of 15 Nm (Min. 14 Nm - Max. 16 Nm) (Sect. 3 - 3, Engine torque settings).

To prevent oil leaks past the contact area between cylinders and crankcase, each time the head is removed, cylinder and piston must be removed as well to clean the mating faces of crankcase and cylinder and restore the spoiled gaskets and O-rings and apply again liquid sealant (Sect. 9 -5, Refitting the cylinder/piston assembly).

Before fitting the head, check that the seal is fitted on the mating surface between head and cylinder (Sect. 9 - 5, Refitting the cylinder/piston assembly).

Tighten the nuts (21) on the stud bolts evenly and gradually in a crosswise pattern using tool 88713.2676 in conjunction with a torque wrench.

Temporary tighten the nuts (21) to a torque of 20 Nm; pre-tightening to a torque of 40 Nm (Min. 38 Nm - Max. 48 Nm); one tight­ening to a torque of 60 Nm (Min. 57 Nm - Max. 63 Nm) (Sect. 3 - 3, Engine torque settings).