10-20
COMPRESSION RELEASE SYSTEM
(SPEC A-D ONLY)
This engine has a compression release system that
decreases the amount of effort required to start the
engine and reduces engine run-on when stopping
(Figure 10-38).
The system works as follows:
1. As the engine is started, a spring holds in the
flyweight which in turn pushes a decompres-
sion pin upward.
2. The decompression pin pushes up on the ex-
haust tappet and opens the exhaust valve mo-
mentarily to release compression and make
starting easier.
3. As the engine speeds up, the flyweight is
forced outward by centrifugal force and the de-
compression pin moves down so that it no lon-
ger opens the exhaust valve.
4. When the engine is stopped, engine speed
drops and the flyweight pulls in and the decom-
pression pin moves up. The pin opens the ex-
haust valve again releasing compression.
The most common cause of problems with this sys-
tem is a faulty spring, the spring may be too long or it
may not be connected. A spring that is too long will
reduce the decompression cutoff speed. Make sure
that the spring is properly attached. If a problem
with the cutoff speed is still suspected, replace the
spring.
CT-1121s
CAMSHAFT
ENGINE START POSITION
ENGINE RUNNING POSITION
DECOMPRESSION
PIN
TAPPET
FLYWEIGHT
SPRING
CAM GEAR
FIGURE 10-38. COMPRESSION RELEASE SYSTEM
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