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6. 4-STROKE: CYLINDER HEAD/VALVES VITALITY 50
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 0.04
Valve clearance (cold)
EX 0.04
Cylinder head compression pressure 142kg/cm
Cylinder head warpage 0.05
IN 25.761 25.65
Camshaft cam height
EX 25.563 25.45
Valve rocker arm to shaft clearance 0.0340.09 0.1
Valve stem-to-guide IN 0.0100.037 0.06
clearance EX 0.0250.052 0.08
IN 29.9 28.4
Valve spring free length
EX 33.5 31.5
Valve spring IN 56kg(at 20.45mm)
compressed force EX 9.511.5kg(at 23.5mm)
6-2