4.1 - | Cylinder head assemblies: checks and adjustments

1 | Closing shim

2 | Camshaft

3 | Opening shim

4 | Valve

Parts catalogue

Cylinder head: timing system
Vertical cylinder head
Horizontal cylinder head

Important
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.
Checking and adjusting valve clearances

Operation | Section reference
Remove the valve covers | N 4.3, Removal of the valve covers
Remove the timing belt covers | N 4.2, Removal of the timing belt covers

Notes
For clarity, the figures show the engine block removed from the frame.
Remove the inspection cover (A) and install service tool no. 88713.0123.
Turn the crankshaft until the mark on the timing belt driveshaft pulley is aligned with the mark on the crankcase cover.
Set the degree wheel of service tool no. 88713.0123 to zero the horizontal cylinder is at top dead centre of the expansion stroke, and therefore we can proceed to check the valve clearances on this cylinder.
To measure valve clearances in the vertical cylinder, rotate the crankshaft counterclockwise through 270° from this position. This will bring the vertical cylinder to top dead centre of the expansion stroke, and therefore we can proceed to check the valve clearances on this cylinder.
Checking the opening clearance (Sa) of the intake/exhaust valves
To check the valve opening clearance (Sa), insert the blade of a feeler gauge between the opening rocker (C) and the shim (3).
Notes
While inserting the blade of the feeler gauge to check the clearance, apply gentle leverage to overcome the force of the closing rocker spring and thus eliminate any play in the rocker mechanism: then check that the shim can rotate freely.
The clearance values must be within the specified limits (Sect. C 1.1, Timing system/valves).
If they are not, remove the opening shim (3), as described in the paragraph “Valve disassembly” Removal of the rocker arms, shims and valves”, Sect. N 4.4, and replace it with a shim of appropriate thickness to obtain the specified clearance.
Notes
Opening rocker arm shims measuring 1.8 to 3.45 are available as replacement parts: each shim is marked with its size.
Checking the closing clearance (Sc) of the intake/exhaust valves
To check the valve closing clearance, insert the blade of a feeler gauge between the closing rocker (C) and the shim (1): the closing clearance (Sc) corresponds to the thickness of the feeler gauge and should allow the free rotation of the shim without any significant play.
The clearance must be within the specified limits (Sect. C 1.1, Timing system/valves).
If it is not, remove the closing shim (1), as described in the paragraph “Removal of the rocker arms, shims and valves”, Sect. N 4.4, and replace it with a shim of suitable thickness to obtain the specified clearance.
Notes
Closing rocker arm shims measuring 2.2 to 4.5 are available as replacement parts: each shim is marked with its size.
Refit the opening and closing shims as described in the paragraph “Refitting the rocker arms, shims and valves”, Sect. N 4.4.
Checking valve lift
Fit the gauge (C) 88765.1581 in correspondence with the fixing hole of the previously removed cylinder head valve cover, as shown in the photo.
Reset the valve opening clearance when the camshaft is in its rest position by fitting a feeler gauge between the upper rocker arm and opening shim.
Notes
This operation is best done using one dial gauge for the exhaust valve and another one for the intake valve.
Make sure the dial gauge fork is centred relative to the valve axis and located against the closing shim.
Set the dial gauge to zero when the valve is fully closed.
Rotate the intake camshaft so as to allow the intake valves to lift fully.
Check that the reading on the dial gauge corresponds to the specified value (Sect. C 1.1, Timing system/valves).
Perform the same procedure for the exhaust valve, fixing the support to the opposite side of the cylinder head.
Refit following the procedure indicated in the previous paragraph “Checking and adjusting valve clearances”.
Remove the tools 88765.1581.

Operation | Section reference
Refit the timing belt covers | N 4.2, Refitting the timing belt covers
Refit the valve covers | N 4.3, Refitting the valve covers

Checking the engine timing

Operation | Section reference
Remove the timing belt covers | N 4.2, Removal of the timing belt covers
Remove the valve covers | N 4.3, Removal of the valve covers

Notes
Engine timing should be checked after changing parts such as camshafts, valves or timing belt rollers or when overhauling badly worn engines.
Remove the spark plugs and install the tool (E) 88765.1297 in the spark plug bore to determine the piston's TDC, along with gauges (C) 88765.1581 and the timing check tool with timing degree wheel (G) 88713.0123).
Reset the opening valve clearance when the camshaft is in rest position by inserting a feeler gauge between the opening rocker arm and the opening shim.
Check that in this condition the camshaft can rotate. If it moves stiffly, use a thinner feeler gauge.
In this condition, with the piston of the horizontal cylinder is at TDC and the valves fully closed as confirmed by the reading on gauge (E), set gauges (C) to zero.
Adjust the timing belt tension as described in Sect. N 4.2 Refitting the timing belt tensioner pulleys).
Turn the degree wheel (G) counterclockwise until the dial gauge (C) on the exhaust side shows a lift of 1 mm. Check that the angular displacement reading on the degree wheel (G) is as specified (Sect. C 1.1, Timing system/valves).
Continue to rotate in the same direction until you obtain a 1 mm lift on the intake side. Check the angular value on the degree wheel.
Continue to rotate until, in correspondence with the closure of the valve for the compression stroke, you obtain a lift of the intake valve of 1 mm on the gauge (C). Check that the angular displacement reading matches the specified value (Sect. C 1.1, Timing system/valves).
Rotate clockwise again until obtaining 1 mm lift of the exhaust valve, on both valve opening and closure.
Check the angular displacement value against the specified value.
Repeat the procedure for the vertical cylinder.
Permissible tolerance for measured values is ±3° with respect to specified values.
Remove the tools used to check engine timing.

Operation | Section reference
Refit the valve covers | N 4.3, Refitting the valve covers
Refit the timing belt covers | N 4.2, Refitting the timing belt covers