Cub Cadet CC 4BP 32cc - Manual (Page 15)

Trouble shooting
12
4. Read the gauge. See Figure 3.6.
NOTE: If the engine has less than 80 psi (5.5
bar) compression, the carburetor will not have
enough vacuum to draw fuel into the engine.
• The engine will have to be torn down to deter-
mine the cause of the low compression.
• If the engine has more than 135 psi (9.3 bar), the
engine will not breath properly.
• Check for restrictions in the exhaust.
To preform a leak down test:
1. Remove the engine cover and spark plug by fol-
lowing the steps described in the spark plug sec-
tion of Chapter 2: Maintenance.
2. Rotate the crankshaft until the piston is at top
dead center.
3. Thread the tester adapter into the spark plug
hole. See Figure 3.7.
NOTE: The adapter from a compression tester
can be used to get the leak down tester adapter
to fit the spark plug hole.
4. Lock the starter cup to prevent the crankshaft
from rotating. See Figure 3.8.
NOTE: A couple of sockets wedged between te
starter cup and the engine block can be used to
lock the engine.
Readings in psi Possible causes
<20
(1.38 Bar) Most likely a stuck valve or
too tight of a valve lash, pro-
vided the starter rope pulls
with normal effort.
20-80
(1.38-5.5 Bar) Valve seat damage or piston
ring and/or cylinder wear.
80-135
(5.5-9.3 Bar) Normal readings
>135
(>9.3 Bar) Excessive valve lash, blocked
exhaust or a partial hydraulic
lock.
Figure 3.6
Figure 3.7
Compression tester
adapter
Leak down tester
Figure 3.8
Starter cup
Sockets