Buell S1 Lightning Workshop Manual page 142

ADJUSTMENT/TESTING
General
When an engine needs repair, it is not always possible to
determine definitely beforehand whether repair is possible
with only cylinder heads, cylinders and pistons disassembled
or whether complete engine disassembly is required for
crankcase repair.
Most commonly, only cylinder head and cylinder repair is
needed (valves, rings, piston, etc.) and it is recommended
procedure to service these units first, allowing engine crank-
case to remain in frame.
See DISASSEMBLING ENGINE FOR CYLINDER HEAD
REPAIR on page 3-8 to strip motorcycle for removal of cylin-
der heads, cylinders, and pistons.
After disassembling "upper end" only, it may be found that
crankcase repair is necessary. In this situation, remove the
engine crankcase from the chassis. See
CRANKCASE OR COMPLETE ENGINE
1
CAUTION
If engine is removed from chassis, do not lay engine on
primary side. Placing engine on primary side will damage
clutch cable end fitting. If fitting is damaged, clutch cable
must be replaced.
Symptoms indicating a need for engine repair are often mis-
leading, but generally, if more than one symptom is present,
possible causes can be narrowed down to make at least a
partial diagnosis. An above-normal consumption of oil, for
example, could be caused by several mechanical faults. See
TROUBLESHOOTING in Section 1. However, when accom-
panied by blue-gray exhaust smoke and low engine compres-
sion, it indicates the piston rings need replacing. Low
compression by itself, however, may indicate improperly
seated valves, in addition to or in lieu of worn piston rings.
Most frequently, valves, rings, pins, bushings, and bearings
need attention at about the same time. If the possible causes
can be narrowed down through the process of elimination to
indicate any one of the above components is worn, it is best
to give attention to all of the cylinder head and cylinder parts.
3-6
Compression Test Procedure
Combustion chamber leakage can result in unsatisfactory
engine performance. A compression test can help determine
the source of cylinder leakage. Use
SION GAUGE (Part No.
A proper compression test should be performed with the
engine at normal operating temperature when possible. Pro-
ceed as follows:
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.
2.
3.
4.
5.
REMOVING ENGINE
on page 3-8.
6.
7.
8.
Ring trouble.
Valve trouble.
Head gasket leak.
HD-33223-1).
1
CAUTION
Disconnect spark plug wires. Clean around plug base
and remove plugs.
Connect compression tester to front cylinder.
With carburetor throttle plates in wide open position,
crank engine continuously through 5-7 full compression
strokes.
Note gauge readings at the end of the first and last com-
pression strokes. Record test results.
Connect compression tester to rear cylinder.
Repeat Steps 3 and 4 on rear cylinder.
Compression is normal if final readings are 120 psi
2
(8.4 kgN/cm ) or more and do not indicate more than a
2
10 psi (0.7 kgN/cm ) variance between cylinders. See
Table 3-1.
Inject approximately 1/2 oz. (15 ml) of SAE 30 oil into
each cylinder and repeat the compression tests on both
cylinders. Readings that are considerably higher during
the second test indicate worn piston rings.
Table 3-1. Compression Test Results
DIAGNOSIS
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.
Compression low on first stroke;
does not build up much on follow-
ing strokes; does not improve con-
siderably with the addition of oil.
Same reaction as valve trouble.
CYLINDER COMPRES-
TEST RESULTS