Test 25 - Check Flywheel - Generac Power Systems GP Series Diagnostic Repair Manual

C
A
B
0
0
F
H
G
0
A. Compressed air in
B. Air pressure regulator
C. Inlet gauge pressure set point
D. Outlet gauge pressure
E. To spark plug hole
F. Regulator adjustment knob
G. Outlet gauge
H. Red range indicates unacceptable leakage
I. Needle indicates minimal air leakage
J. Green range indicates acceptable leakage
Figure 4-16. Cylinder Leakdown Tester
Procedure
Shut off the fuel supply.
1.
Remove spark plug.
2.
Gain access to flywheel.
3.
Remove valve cover.
4.
Rotate engine crankshaft until piston reaches top
5.
dead center (TDC). Both valves should be closed.
Lock flywheel at top dead center.
6.
Attach cylinder leak down tester adapter to spark
7.
plug hole.
Connect an air source of at least 90 psi to the leak
8.
down tester.
Adjust regulated pressure on gauge to 80 psi.
9.
Read right hand gauge on tester for cylinder
10.
pressure. 20 percent
acceptable. Use good judgment, and listen for air
escaping at carburetor, exhaust, and crankcase
breather. This determines where the fault lies.
Results
•
Air escapes at carburetor – check intake valve.
•
Air escapes through exhaust – check exhaust
valve.
•
Air escapes through breather – check piston rings.
•
Air escapes from cylinder head – replace head
gasket.
Check Compression
To check engine compression, remove spark plug. Insert
an automotive type compression gauge into the spark
Diagnostic Repair Manual
D
E
I
J
leakage is normally
plug hole. Crank engine until there is no further in
pressure. The highest reading obtained is engine
compression pressure.
Minimum Allowable Compression Pressure Cold
Engine – 60 psi
If compression is poor, look the following causes:
•
Loose cylinder head bolts
•
Failed cylinder head gasket
•
Burned valves or valve seats
•
Insufficient valve clearance
•
Warped cylinder head
002419
•
Warped valve stem
002419
•
Worn or broken piston ring(s)
•
Worn or damaged cylinder bore
•
Broken connecting rod
•
Worn valve seats or valves
•
Worn valve guides
NOTE: Refer to Engine Service Manual Part Number
0C1103A for further engine service information on the
410cc engine.
Test 25 – Check Flywheel
General
Theory
See Figure 4-17. In Test 19, a spark tester was used to
check for engine ignition. If sparking or weak spark
occurred, a possible cause might be the ignition
magneto. This test checks magnetism of flywheel and will
check the flywheel key.
Figure 4-17. Engine Ground Harness
Procedure
Check flywheel magnet by holding a screwdriver at
1.
extreme end of handle with its point down. When
the tip of screwdriver is moved to within 3/4 inch
(19mm) of magnet, the blade should be pulled in
against the magnet.
For rough running or hard starting engines, check
2.
flywheel key. The flywheel's taper is locked on the
crankshaft taper by the torque of the flywheel nut.
Section 4 Engine Diagnostic Tests
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