detected by a buildup of air pressure
when thumb is held over open spark
Continue rotating crankshaft until
piston contacts arm of indicator and moves pointer to any
marker on Indicator face.
Note mark reached and record
Move crankshaft slowly in direction
of rotation until Indicator pointer shows that piston has
moved to top of stroke and is going down.
pointer moves to exact same position as In step 6.
Read and record protractor reading
True top dead center is halfway
between two protractor readings
Back up crankshaft and rotate it
forward in direction of rotation until protractor pointer
indicates top dead center (in degrees).
Loosen pointer and set to zero
without moving crankshaft.
When reinstalling pointer, allow for
gear backlash by moving pointer
opposite its direction of rotation.
Recheck top dead center position
to ensure that a given piston position will result In equal
protractor readings before and after zero mark.
Establishing crankshaft position upon
piston position indicator. The following steps outline
another method of establishing the crankshaft position.
Use piston position indicator with
18mm threads for 18mm spark plug
threads and 14mm threads for 14mm
spark plug threads. Damage to
threads may otherwise result.
Remove spark plug and install
piston position indicator, as shown in figure 7-16, with
correct arm and calibrated scale.
Rotate crankshaft in direction of
rotation until piston is coming up on compression stroke.
assembly and screw housing into spark plug bushing until
it seats firmly. Insert indicator assembly into body, as
shown in figure 7-16.
4 Push slide pointer upward in slot
until it reaches end of slot and is stopped by pivot arm.
Pull crankshaft slowly in direction of
rotation until arm moves pointer maximum distance and
starts to move back.
Figure 7-16. Installation of Piston Position Indicators