Diagnosing Smoking Engine Or High Oil Consumption - Buell P3 Service Manual

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Compression Test Procedure
Combustion chamber leakage can result in unsatisfactory
engine performance. A compression test can help determine
the source of cylinder leakage. Use CYLINDER COMPRES-
SION GAUGE (Part No. HD-33223-1).
A proper compression test should be performed with the
engine at normal operating temperature when possible. Pro-
ceed as follows:
IMPORTANT NOTE
After completing the compression test(s), make sure that
the throttle plate is in the closed position before starting
engine. Engine will start at an extremely high RPM if
throttle plate is left open.
1. Disconnect spark plug wire. Clean around plug base and
remove plug.
2. Connect compression tester to cylinder.
3. With carburetor throttle plates in wide open position,
crank engine continuously through 5-7 full compression
strokes.
4. Note gauge readings at the end of the first and last com-
pression strokes. Record test results.
5. Compression is normal if final readings are 120 psi
(827 kPa) or more.
6. Inject approximately 1/2 oz. (15 ml) of SAE 30 oil into cyl-
inder and repeat the compression test. Readings that are
considerably higher during the second test indicate worn
piston rings.
Table 3-17. Compression Test Results
DIAGNOSIS
Ring trouble Compression low on first stroke;
tends to build up on the following
strokes but does not reach normal;
improves considerably when oil is
added to cylinder.
Valve trouble Compression low on first stroke;
does not build up much on follow-
ing strokes; does not improve con-
siderably with the addition of oil.
Head gasket leak Same reaction as valve trouble.
Cylinder Leakage Test
The cylinder leakage test pinpoints engine problems includ-
ing leaking valves, worn, broken or stuck piston rings and
blown head gaskets. The cylinder leakage tester applies com-
pressed air to the cylinder at a controlled pressure and vol-
ume, and measures the percent of leakage from the cylinder.
Use a CYLINDER LEAKDOWN TESTER (Part No. HD-
35667A) and follow the specific instructions supplied with the
tester.
The following are some general instructions that apply to
Buell motorcycle engines:
1. Run engine until it reaches normal operating tempera-
ture.
TEST RESULTS
2. Stop engine. Clean dirt from around spark plug and
remove spark plug.
3. Remove air cleaner and set carburetor throttle in wide
open position.
4. Remove timing inspection plug from crankcase.
5. The piston, in cylinder being tested, must be at top dead
center of compression stroke during test.
6. To keep engine from turning over when air pressure is
applied to cylinder, engage transmission in fifth gear and
lock the rear brake.
7. Following the manufacturer's instructions, perform a cyl-
inder leakage test on the front cylinder. Make a note of
the percent leakdown. Any cylinder with 12% leakdown,
or more, requires further attention.
8. Refer to Table 3-18. Listen for air leaks at carburetor
intake, exhaust, head gasket and timing inspection hole.
NOTE
If air is escaping through valves, check push rod length.
IMPORTANT NOTE
After completing the compression test(s), make sure that
the throttle plate is in the closed position before starting
engine. Engine will start at an extremely high RPM if
throttle plate is left open.
Table 3-18. Air Leakage Test
AIR LEAK LOCATION
Carburetor intake
Exhaust pipe
Timing inspection hole
Head gasket
Diagnosing Smoking Engine or High Oil
Consumption
Perform Compression Test Procedure
Test as described previously. If further testing is needed,
remove suspect head(s) and inspect the following:
Valve guide seals.
Valve guide-to-valve stem clearance.
Gasket surface of both head and cylinder.
POSSIBLE CAUSES
Intake valve leaking.
Exhaust valve leaking.
Piston rings leaking.
Worn or broken piston.
Worn cylinder.
Leaking gasket.
or Cylinder Leakage
2007 Buell P3: Engine 3-7