Kymco MO Movie125, MO Movie 150 Service Manual - chap 07 (testa e valvole)
7. CYLINDER HEAD/VALVES
7-0
7
0.8kg-m
1.2kg-m
2.0kg-m
7. CYLINDER HEAD/VALVES
7-1
SERVICE INFORMATION
GENERAL INSTRUCTIONS
• The cylinder head can be serviced with the engine installed in the frame.
• When assembling, apply molybdenum disulfide grease or engine oil to the valve guide movable
parts, valve arm and camshaft sliding surfaces for initial lubrication.
• The camshaft is lubricated by engine oil through the cylinder head engine oil passages. Clean and
unclog the oil passages before assembling the cylinder head.
• After disassembly, clean the removed parts and dry them with compressed air before inspection.
• After removal, mark and arrange the removed parts in order. When assembling, install them in the
reverse order of removal.
SPECIFICATIONS
Item
Standard (mm)
Service Limit (mm)
IN
0.12
æ
EX
0.12
æ
Cylinder head compression pressure
12.8kg/cm≤ñ 570rpm
Cylinder head warpage
æ
IN
25.965
25.57
EX
25.810
25.41
IN
10.000_ 10.015
10.10
EX
10.000_ 10.015
10.10
Valve rocker arm shaft
IN
9.972_ 9.987
9.91
O.D.
EX
9.972_ 9.987
9.91
IN
1.0
1.8
EX
1.0
1.8
IN
4.975_ 4.990
4.90
EX
4.955_ 4.970
4.90
IN
5.000_ 5.012
5.03
EX
5.000_ 5.012
5.03
Valve stem-to-guide
IN
0.010_ 0.037
0.08
clearance
EX
0.030_ 0.057
0.10
Valve clearance (cold)
Valve rocker arm I.D.
Valve stem O.D.
Valve guide I.D.
SERVICE INFORMATION
.....................
7-1 VALVE GUIDE REPLACEMENT
...........
7- 9
TROUBLESHOOTING
............................
7-2 VALVE SEAT INSPECTION & REFACING
.....
7-10
CAMSHAFT REMOVAL
........................
7-3 CYLINDER HEAD ASSEMBLY
..............
7-12
CYLINDER HEAD REMOVAL
..............
7-6 CYLINDER HEAD INSTALLATION
.....
7-13
CYLINDER HEAD DISASSEMBLY
.......
7-7 CAMSHAFT INSTALLATION
...............
7-14
Camshaft cam height
Valve seat width
7. CYLINDER HEAD/VALVES
7-2
TORQUE VALUES
Cylinder head nut 2.0kg-m Apply engine oil to threads
Valve clearance adjusting nut 0.9kg-m Apply engine oil to threads
SPECIAL TOOLS
Valve spring compressor
Valve seat cutter, 24.5mm 45° IN/EX
Valve seat cutter, 25mm Plane cutter 32° IN
Valve seat cutter, 22mm Plane cutter 32° EX
Valve seat cutter, 26mm Plane cutter 60° IN/EX
Cutter clip, 5mm
Valve spring compressor attachment
Valve wrench
Valve guide driver
Valve guide reamer
TROUBLESHOOTING
• The poor cylinder head operation can be diagnosed by a compression test or by tracing engine
top-end noises.
Poor performance at idle speed White smoke from exhaust muffler
• Compression too low • Worn valve stem or valve guide
• Damaged valve stem seal
Compression too low
• Incorrect valve clearance adjustment Abnormal noise
• Burned or bend valves • Incorrect valve clearance adjustment
• Incorrect valve timing • Sticking valve or broken valve spring
• Broken valve spring • Damaged or worn camshaft
• Poor valve and seat contact • Worn cam chain guide
• Leaking cylinder head gasket • Worn camshaft and rocker arm
• Warped or cracked cylinder head
• Poorly installed spark plug
Compression too high
• Excessive carbon build-up in combustion
chamber
7. CYLINDER HEAD/VALVES
7-3
CAMSHAFT REMOVAL
Remove the center cover. (!2-3)
Remove the four cylinder head cover bolts to
remove the cylinder head cover.
Remove the two nuts attaching the secondary
air inlet tube.
Remove the cam chain tensioner cap screw
and the O-ring.
Turn the cam chain tensioner screw clockwise
to tighten it.
Turn the flywheel counterclockwise so that
the “T” mark on the flywheel aligns with the
index mark on the crankcase to bring the
round hole on the camshaft gear facing up to
the top dead center on the compression
stroke.
Cylinder Head Cover
O-ring
Tensioner Screw
Round Hole
Camshaft Gear
Screw
Punch Marks
7. CYLINDER HEAD/VALVES
7-4
Remove the two cylinder head bolts.
Remove the four cylinder head nuts and
washers.
Remove the camshaft holder and dowel pins.
Remove the camshaft gear from the cam chain
and remove the camshaft.
CAMSHAFT INSPECTION
Check each cam lobe for wear or damage.
Measure the cam lobe height.
Service Limits:
IN : 25.57mm replace if below
EX: 25.41mm replace if below
Cam Chain
Camshaft Gear
Diagonally loosen the cylinder head nuts
in 2 or 3 times.
＊
Camshaft Holder
Nut
Bolt
Washer
Dowel Pins
Camshaft
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