Kohler CV11-16, Service Manual

Page: 26 / 150

3.4
Section 3
Troubleshooting
Compression Test
These engines are equipped with an automatic
compression release (ACR) mechanism. Because
of the ACR mechanism, it is diffi cult to obtain an
accurate compression reading. As an alternate, use
the leakdown test described below.
Cylinder Leakdown Test
A cylinder leakdown test can be a valuable alternative
to a compression test. By pressurizing the combustion
chamber from an external air source you can
determine if the valves or rings are leaking, and how
badly.
The tester listed on page 2.2 is a relatively simple,
inexpensive leakdown tester for small engines. The
tester includes a quick disconnect for attaching the
adapter hose and a holding tool.
Leakdown Test Instructions
1. Run engine for 3-5 minutes to warm it up.
2. Remove spark plug(s) and air fi lter from the
engine.
3. Rotate the crankshaft until the piston is at top
dead center (TDC) of the compression stroke.
You will need to hold the engine in this position
while testing. The holding tool supplied with
the tester can be used if the PTO end of the
crankshaft is accessible. Slide the holding tool
onto the crankshaft, align the slot/hole with one
of mounting hold on the PTO face, and tighten
it onto the crankshaft. Install a 3/8" breaker bar
into the slot or square hole of the holding tool,
so it is perpendicular to both the holding tool and
crankshaft PTO, or insert a shoulder bolt through
the slot and thread it into the mounting hole. If the
fl ywheel end is more accessible, you can use a
breaker bar and socket on the fl ywheel nut/screw
to hold it in position. You may need an assistant
to hold the breaker bar during testing. If the
engine is mounted in a piece of equipment, you
may be able to hold it by clamping or wedging a
driven component. Just be certain that the engine
cannot rotate off of TDC in either direction.
4. Install the adapter into the spark plug hole, but do
not attach it to the tester at this time.
5. Connect an adequate air source to the tester.
6. Turn the regulator knob in the increase
(clockwise) direction until the gauge needle is in
the yellow ‘‘set’’ area at the low end of the scale.
7. Connect tester quick-disconnect to the adapter.
Note the gauge reading and listen for escaping
air at the carburetor intake, exhaust outlet, and
crankcase breather.
8. Check your test results against the table below:
Leakdown Test Results
Air escaping from crankcase breather ........................................... Defective rings or worn cylinder walls.
Air escaping from exhaust system................................................. Defective exhaust valve.
Air escaping from carburetor ......................................................... Defective intake valve.
Gauge reading in ‘‘low’’ (green) zone ............................................ Piston rings and cylinder in good condition.
Gauge reading in ‘‘moderate’’ (yellow) zone .................................. Engine is still usable, but there is some wear
present. Customer should start planning for
overhaul or replacement.
Gauge reading in ‘‘high’’ (red) zone ............................................... Rings and/or cylinder have considerable wear.
Engine should be reconditioned or replaced.