KYMCO Mongoose 50-2T, Service Manual

Page: 112 / 258

7
. CYLINDER HEAD/VALVES
(90cc/70cc/50cc-4T)
7-2
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
90cc mm (in)
Item Standard Service Limit
IN 0.1 (0.004)
⎯
Valve clearance (cold)
EX 0.1 (0.004)
⎯
Cylinder head compression pressure 16 kg/cm
²
(1600 kpa, 227.2 psi)
⎯
Cylinder head warpage
⎯
0.05 (0.002)
IN 26.4881 (1.029524) 26.33 (1.0532)
Camshaft cam height
EX 25.8073 (1.032292) 25.65 (1.026)
Valve rocker arm to shaft clearance
0.034
～
0.09 (0.00136
～
0.0036) 0.1 (0.004)
Valve stem-to-guide IN 0.01
～
0.037 (0.0004
～
0.00148) 0.06 (0.0024)
clearance
EX 0.025
～
0.052 (0.001
～
0.00208) 0.08 (0.0032)
IN 32.3 (1.292) 30.8 (1.232)
Valve spring free length
EX 35 (1.4) 33.5 (1.34)
IN 3.47
～
4.27 kg at 26 mm (1.04 in)
⎯
Valve spring
compressed force
EX 8.29
～
10.19 kg at 29 mm (1.16 in)
⎯
70cc mm (in)
Item Standard Service Limit
IN 0.04 (0.0016)
⎯
Valve clearance (cold)
EX 0.04 (0.0016)
⎯
Cylinder head compression pressure 14 kg/cm
²
(1400 kpa, 198.8 psi)
⎯
Cylinder head warpage
⎯
0.05 (0.002)
IN 25.761 (1.03044) 25.65 (1.026)
Camshaft cam height
EX 25.604 (1.02416) 25.5 (1.02)
Valve rocker arm to shaft clearance
0.034
～
0.09 (0.00136
～
0.0036) 0.1 (0.004)
Valve stem-to-guide IN 0.01
～
0.037 (0.0004
～
0.00148) 0.06 (0.0024)
clearance
EX 0.025
～
0.052 (0.001
～
0.00208) 0.08 (0.0032)
IN 29.9 (1.196) 28.4 (1.136)
Valve spring free length
EX 33.5 (1.34) 32 (1.28)
IN 4.3 kg at 22.45 mm (0.898 in)
⎯
Valve spring
compressed force
EX 8.4 kg at 25.25 mm (1.01 in)
⎯