Kohler K91 Service Manual page 75

BRACKET
(PART OF
COIL)
Figure 8-6. Typical 8reakerless Ignition Coil.
Breakerless Ig nition System Timing
Because there are no breaker points in this sys­
tem , there is no requirement for timing . However,
there is a requirement for positioning the trigger
module for proper relationship with the flywheel
projection . The gap between the projection and
trigger module is normally set between . 005 and
. 0 1 0 " . This setting is not critical , but selecting a
. 005 " gap promotes better cold weather starting .
Set the gap as follows.
1 . Remove the spark plug lead to prevent inad­
vertent starting .
2 . Rotate the flywheel so that the projection is
aligned with the trigger module.
3 . Loosen the cap screws o n the trigger module
bracket and insert a . 005 " feeler gauge in the
gap .
4 . Move t h e trigger module until i t touches the
feeler gauge , making sure that the flat sur­
faces of module and projection are parallel .
5 . Tighten the cap screws and replace the spark
plug lead .
The trigger module has two clip-on type terminals .
Make sure that the leads are connected as shown
in Figure 8-7 .
TRIGGER MODULE (BREAKERLESS)
The trigger module used on breakerless ignition
systems is a solid state device which includes
diodes , resistor, sensing coil and magnet plus an
electronic switch called an SCR . The terminal
marked A must be connected to the alternator
I
while terminal must be connected to the ignition
switch or ignition coil . Operating with these leads
reversed will cause damage to the solid state de-
---- - T O TRI GGER
&
SWI TCH
vices . If a faulty trigger module is suspected , dis­
connect and remove the trigger from the engine
and perform the following tests with a flashlight
tester. Reset air gap when reinstalling trigger.
Diode Test
Turn tester switch ON and connect one lead to
I
the terminal and the other to the A terminal then
reverse these leads--light should come on with
leads one way but not the other way . If light stays
on or off both ways , this indicates diodes are
faulty--replace trigger module.
SCR Test
Turn tester on then connect one lead to the
terminal and the other to the trigger mounting
bracket .
NOTE : If light comes o n , reverse the leads as the
light must be off initially for this test .
Lightly tap magnet with a metal object--when this
is done , tester light should come on and stay on
u ntil leads are disconnected . If light does not
come on , this indicates SCR is not switching prop­
erly in which case trigger module should be re­
placed .
IGNITION COILS
Breakerless Type Ignition Coil
Use an ohmmeter to test breakerless type coil
assembly. (A) -- Remove high tension lead from
terminal on coil . I nsert one ohmmeter lead in coil
terminal and the other to the coil mounting brack-
et . A resistance of about 1 1 , 500 ohms should be
indicated here . (B) -- Connect one tester lead to
the coil mounting bracket and the other to the
ignition switch wire. Continuity should not be indi-
cated here. Replace ignition coil assembly if wrong
results are obtained from either of these tests.
Magneto and Battery System Breaker
Points
Engine operation is g reatly affected by breaker
point condition and adjustment of the gap . If
points are burned or badly oxidized , little or no
current will pass . The engine may not operate at
all or may miss at high speed . Size of the breaker
point gap affects the amount of time the points
are open and closed . If the gap is set too wid e ,
they will open too early a n d close too late . A defi­
nite period of time is required for the field to build
in the ignition coil . If the points are closed for too
long or too short a period , a weak spark will be
produced by the coil .
Figure 8-8 shows the effects of too little and too
much capacitance in the condenser. Severe metal
buildup on either contact indicates that the con­
denser is not properly matched to the rest of the
system and should be replaced .
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