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.

Look through the inspection window in the generator cover. The flywheel mark and the cover mark (A) of both cylinders should be aligned.

Reset the degree wheel of tool part no. 88713.0123: the horizontal piston is at TDC in the combustion stroke and therefore you can proceed with checking valve clearance on this cylinder head.

To measure valve clearance in the vertical cylinder, rotate the crankshaft counterclockwise through 270°. This will bring the vertical piston at TDC during the combustion stroke that is the correct position for checking valve clearance on this cylinder head.

To check opening clearance (Sa), slide a feeler gauge between opening rocker arm (B) and shim (3). Measured clearance must be within the specified limits (Sect C1.1, Timing/valves).

If the clearance measured is outside the specified limits, remove the opening shim (3) as described under paragraph "Removing the valves" in Section N 4.4, and replace it with a suitable one to reach the recommended assembly clearance.

When performing this check and inserting the feeler gauge, pay attention to overcome rocker arm closing spring force to take up rocker arm operating play: for this purpose, ensure that shim can rotate freely.

When checking closing clearance, use a screwdriver to overcome the preload of closing rocker arm spring, thus taking up any clearance between camshaft and rocker arm. Fit the feeler gauge between closing rocker arm (D) and shim (1): closing clearance (Sc) corresponds to gauge thickness when it allows the shim to freely turn, with no remarkable play.

Clearance must be within the specified limits (Sect. C 1.1, Timing/valves).

If not so, remove the closing shim (1) as described in paragraph "Removing the valves", Sect. N 4.4, and fit a shim of the adequate size to obtain specified assembly clearance.

Refit the opening and closing shims as described in paragraph "Refitting the valves" Sect. N 4.4.

Fit dial gauge (C) part no. 88765.1058 into the hole of the head cover, as shown.

With the camshaft at rest position, take up valve opening clearance fitting a suitably sized feeler gauge between upper rocker arm and opening shim.

Check that the reading on the dial gauge corresponds to the recommended value (Sect. C 1.1, Timing/valves).

Remove tools part no. 88765.1058.

Engine timing should be checked after replacing such component parts as camshafts, valves or timing belt rollers or when overhauling badly worn engines.

Remove the spark plugs and fit tool (E) part no. 88765.1297 in the spark plug hole and determine piston top dead center with gauges (C) part no. 88765.1058 and timing gauge (hub part no. 88713.0123 and degree wheel (G) part no. 98112.0002).

With the camshaft at rest position, take up valve opening clearance fitting a suitably sized feeler gauge (D) between opening rocker arm and opening shim.

In this condition, the piston of the horizontal cylinder is at TDC with the valves fully closed - verify looking at gauge (E). Set dial gauges (C) to zero.

- Horizontal belt 145 Hz;

- Vertical belt 160 Hz.

Turn degree wheel (G) counter clockwise until dial gauge (C) placed at the exhaust end reads 1 mm lift. Check that angle reading in degrees on the degree wheel (G) is as specified (Sect. C 1.1, Timing/valves).

Rotate in the same direction until obtaining 1 mm lift on the intake end. Check degrees on degree wheel.

Reverse rotation (i.e., turn clockwise) of degree wheel (G) until gauge (C) points 1 mm lift of intake valve. Check degrees again.

Rotate clockwise again until obtaining 1 mm lift of the exhaust valve.

Allowed tolerance for measured values is ±3° with respect to specified values.