Engine Manual

ENGINE MANUAL

MODELS G-IV- A2, A5, B, B5

ENGINE TIMING

1. Valve Clearance Adjustment

To adjust the clearance between the valve end and the adjustment screw on the rocker arms, it is necessary to rotate the crankshaft until the piston is TDCC. In this position, the valves are closed, which will allow, with a very slight pressure., a feeler gauge of 0. 3 mm (.012 in.) to be slid between the valve end and the rocker arm adjustment screw. The clearance corresponds to an engine temperature of 15°C. (59°F.) In case of a need to adjust the valve clearance, loosen the adjustment screw nut, adjust and torque down. Check valve clearance again. An easy check of piston position is given by the position of the screw located at the crankshaft in the area of the propeller shaft. (see fig. 24)

The position of firing and end of exhaust are differentiated by the position of the exhaust valve, visible from the exterior, resting on its seat when the piston is TDCC and slightly open when the piston is to the end of exhaust. (see fig. 26)

2. Internal Engine Timing

A check on the internal timing is done on cylinder No. 1. The marks located on the accessory section gears refer to the approximate moment of the opening of the intake valve on cylinder No. 1.

Do as follows:

a. Install a piston position indicator on the front spark plug opening of cylinder No. 1.

b. Install a protractor on the crankshaft with an indicator. (see fig. 27)

c. Place piston No. 1 in TDCI (both valves open) with the help of the piston position indicator.

Fig. 28 - Rotate crankshaft and protractor with lever (A) until needle (D) of the piston position indicator coincides with the center line of the piston position indicator sector. Now the arrow (C) will show an angular position over the protractor (B). Example: 16°BTDC Fig 29 - Continue rotating lever A)until needle (D), after following a swing, return to the center line of the piston position indicator sector. The arrow (C) will show, for example,14° ATDC.

Fig. 30 - Without moving lever (A), move arrow an angle equal to half of the difference of the values previously obtained. Example: ( 16 ° - 14 °) 2 = 1°

The arrow (C) must show 15°.

Fig. 31 - Rotate lever (A) until the 0° position in the protractor coincides with arrow (C). Now the piston will be TDC.

d. Check that the clearances are 0.3 mm. (.012 in.)

e. Rotate the crankshaft in the direction opposite to normal rotation about 45°. Then rotate in the direction of normal rotation slowly (jogging). Check the instant in which the spring retainer can be rotated. This will correspond with opening of the intake valve. Read the advance in degrees on the protractor.

f. Rotate the crankshaft in a manner similar to the above, to check closing of intake and exhaust valves and opening of exhaust.

If the camshaft drive mechanism is properly synchronized and the valves are properly adjusted, the readings should coincide with the timing specifications. (See table of engine characteristics.)

3. Magneto Timing a. Right Magneto

Install the protractor on the crankshaft and the indicator arrow. Rotate the crankshaft in the direction of normal rotation until piston No. 1 is TDCC (Follow the instructions previously shown for engine timing.) The arrow (C) will show O° on the protractor (B) fig. 31. Rotate the crankshaft in the direction opposite to normal rotation approximately ¼ of a turn and then in normal direction of rotation until 38 shows in front of the arrow, which corresponds with the proper magneto timing. Rotate the magneto shaft until the metal segment on the distributor is located in front of the mark on the magneto housing. (fig. 32) Holding the distributor rotor, with one hand, rotate the magneto shaft, slowly with the other hand, in the direction opposite to normal rotation until in the position of maximum advance. In this instant the points should begin to open (check with timing light). Install the magneto on the engine. Make sure the gasket and "0” ring are in proper position. Be careful not to change the angular position of the magneto. Rotate the magneto within the extreme positions allowed by the slots, checking the points opening and closing with the timing light. Fasten the magneto to the engine until it is firmly seated on the accessory section housing, but allowing it to rotate for fine adjustment.

Check the proper magneto timing by rotating the crankshaft of a turn in the direction opposite to normal direction of rotation. Then rotate the crankshaft, slowly, in the normal direction of rotation until the timing light indicates point opening. Check the angular position of the crankshaft to coincide with the 38°position. Adjust if necessary and tighten and safety the 3 nuts. b. Left Magneto

Set cylinder No. 1 in TDCC and rotate the crankshaft 180° in the normal direction of rotation. Then rotate crankshaft ¼ of a turn in the direction opposite to normal direction of rotation and then, slowly in the normal direction of rotation until 34° (B, B5 engines) or 36° (A,A2,A5 engines) shows in front of the arrow which corresponds to the proper magneto timing

Rotate the magneto shaft until the distributor is in the position shown in fig. 33. Holding the distributor rotor with one hand, rotate very slowly, with the other hand, the magneto shaft in the direction opposite to normal rotation, until in the position of maximum advance. In this instant the points should begin to open (check with -timing light). Install the magneto in the engine and follow the same directions as for the Right Magneto.

JVM - 10-21-78