Tecumseh ECV100 - 120 Technician's Handbook page 73

Begin the procedure by replacing the points if necessary.
To do this remove the nut that secure the movable portion
of the breaker points. Remove the screw from the stationary
portion of the breaker points and the worn breaker point
assembly. Install a new breaker point assembly and adjust
the point gap. This is done by rotating the crankshaft until
the point arm is resting on the high side of the ignition
cam. Set the point gap by loosening the screw on the
movable point set and insert a feeler gauge per
specification. Adjust the point gap so that a light drag is
felt on the feeler gauge. Tighten the screw and recheck the
gap. Leave the leads unattached for the timing procedure.
Use this procedure on all standard point ignition systems
when point replacement is necessary (diag. 21).
Install a dial indicator (Part # 670241), equipped with the
correct tip on the extender leg. Use the small tip for engines
with timing dimensions of between top dead center (T.D.C.)
and .050" (1.27 mm) before top dead center (B.T.D.C.).
Use the large tip for engines with timing dimensions of
between .051" (1.295 mm) B.T.D.C. to .150" (3.81 mm)
B.T.D.C. Make sure to secure the extender leg in position
to locate the tip directly over the piston head. Loosen the
screw on the side of the adaptor sleeve to allow the sleeve
to be turned into the threads of the spark plug hole, not the
entire dial indicator. This will ensure the proper location of
the tip. Once the adapter sleeve is secured in the hole,
tighten screw on sleeve adaptor to prevent the dial from
moving up or down, which would give a false reading (diag.
22).
Find T.D.C. with both valves closed by rotating the
crankshaft clockwise when looking at the magneto end of
the crank, until the needle on the dial stops and reverses
direction. Where the needle stops is T.D.C. Loosen the
screw on the dial, and rotate the dial so that zero is lined
up with the needle at T.D.C. Tighten the screw on the dial
to secure it in place (diag. 23).
While watching the needle on the dial indicator, rotate the
crankshaft counterclockwise when looking at the magneto
end of the crank, .010" (.254 mm) past the B.T.D.C.
dimension. Then rotate the crankshaft clockwise to the
proper B.T.D.C. dimension, this will take out any slack
between the connecting rod and crankshaft assembly.
Example: If the specification of .080" (2.032 mm) is the
B.T.D.C. dimension, rotate the crankshaft counter-
clockwise so that the needle on the dial indicator travels to
.090" (2.286 mm) B.T.D.C. (diag. 24), then rotate the
crankshaft clockwise so that the needle travels to the
specified dimension of .080" (2.032 mm) B.T.D.C. (diag.
25).
Next, if the original breaker points are being used,
disconnect the leads from the point terminal. Reinstall the
nut & tighten. Connect one lead of a continuity light, or
ohmmeter to the point terminal and the other lead to a
good ground. Loosen the two bolts holding down the stator
and rotate the stator until the continuity light or ohmmeter
indicates a break in the circuit. Torque down the stator
bolts while maintaining the stator plate position and the
timing procedure is completed. Reconnect the leads on
the point terminal and tighten the nut making sure that the
leads do not touch the flywheel (diag. 26).
CRANKSHAFT
DIAL AT
.090"
(2.286 mm)
(continued on top of next page)
ARM
PIVOT
SLEEVE
DIAL AT 0"
DIAL AT
.080"
(2.032 mm)
24
IGNITION
CAM
POINTS
21
DIAL SCREW
SLEEVE
SCREW
22
23
25
26
69