Kymco MO KXR 250 Service Manual - chap 07 (testa cilindro e valvole)
7. CYLINDER HEAD/VALVES
7-0
Mongoose/KXR 250
7
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
__________________________________________________________________________________
CYLINDER HEAD/VALVES
__________________________________________________________________________________
SERVICE INFORMATION -------------------------------------------- 7- 2
TROUBLESHOOTING ------------------------------------------------- 7- 3
CYLINDER HEAD COVER-------------------------------------------- 7- 4
CAMSHAFT/CAMSHAFT HOLDER --------------------------------- 7- 4
CYLINDER HEAD------------------------------------------------------ 7- 9
7
7. CYLINDER HEAD/VALVES
7-1
Mongoose/KXR 250
7. CYLINDER HEAD/VALVES
7-2
Mongoose/KXR 250
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
0.1
æ
EX
0.1
æ
Cylinder head compression pressure
15±2kg/cm_
Cylinder head warpage
æ
0.05
IN
34.287
34.15
EX
34.1721
34.05
Valve rocker arm to shaft clearance
0.034_ 0.09
0.1
Valve stem-to-guide
IN
0.010_ 0.037
0.06
clearance
EX
0.025_ 0.052
0.08
IN
30.9
29.4
Valve spring free length
EX4139
IN
10.20_ 11.84kg(at 18.05mm)
æ
Valve spring
compressed force
EX
19.14_ 22.02kg(at 21.5mm)
æ
IN
0.8
æ
Valve spring tilt
EX
1.07
æ
Valve clearance (cold)
Camshaft cam height
7. CYLINDER HEAD/VALVES
7-3
Mongoose/KXR 250
TORQUE VALUES
Cylinder head cover bolt 0.8_ 1.2kgf-m
Cam shaft hold nut 2.3_ 2.7kgf-m Apply engine oil to threads
Tappet adjusting nut 0.7_ 1.1kgf-m
SPECIAL TOOLS
Valve spring compressor E040
Tappet adjuster E012
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
Loading...