Kymco MO GD125, MO GD 150 Service Manual - chap 06 (testa cilindro valvole)

6. CYLINDER HEAD/VALVES

6-0

GRAND DINK 125/15 0

6 .

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CYLINDER HEAD/VALVES

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SCHEMATIC DRAWING ---------------------------------------------- 6- 1

SERVICE INFORMATION -------------------------------------------- 6- 2

TROUBLESHOOTING ------------------------------------------------- 6- 3

CYLINDER HEAD COVER REMOVAL ----------------------------- 6- 4

CAMSHAFT REMOVAL----------------------------------------------- 6- 4

CYLINDER HEAD REMOVAL --------------------------------------- 6- 6

CYLINDER HEAD DISASSEMBLY --------------------------------- 6- 7

CYLINDER HEAD ASSEMBLY -------------------------------------- 6- 8

CYLINDER HEAD INSTALLATION -------------------------------- 6- 9

CAMSHAFT INSTALLATION---------------------------------------- 6-10

CYLINDER HEAD COVER INSTALLATION---------------------- 6-11

6

6. CYLINDER HEAD/VALVES

6-1

GRAND DINK 125/15 0

SCHEMATIC DRAWING

6. CYLINDER HEAD/VALVES

6-2

GRAND DINK 125/15 0

SERVICE INFORMATION

GENERAL INSTRUCTIONS

• The cylinder head can be serviced with the engine installed in the frame. Coolant in the radiator

and water jacket must be drained first.

• When assembling, apply molybdenum disulfide grease or engine oil to the valve guide movable

parts and valve arm sliding surfaces for initial lubrication.

• The valve rocker arms are 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

Standard (mm)

Service Limit (mm)

Item

SH30DA

SH25DA

SH30DA

SH25DA

IN

0.10

ææEX

0.10

æ

Cylinder head compression pressure

15kg/cm_

æ

Cylinder head warpage

æ

0.05

0.05IN30.8763

30.8763

30.75

30.75EX30.4081

30.4081

30.26

IN

10.00_ 10.018

10.10

EX

10.00_ 10.018

10.10

Valve rocker arm shaft

IN

9.972_ 9.987

9.9

O.D.EX9.972_ 9.987

9.972_ 9.987

9.9

9.9IN1.2

1.2

1.8

1.8EX1.2

1.2

1.8

IN

4.990_ 4.975

4.925

EX

4.970_ 4.955

4.915

IN

5.00_ 5.012

5.03

EX

5.00_ 5.012

5.03

Valve stem-to-guide

IN

0.010_ 0.037

0.08

clearance

EX

0.030_ 0.057

0.10

TORQUE VALUES

Cylinder head cap nut 19.6N-m Apply engine oil to threads Valve clearance adjusting nut 8.8N-m Apply engine oil to threads Cylinder head cover bolt 7.8_ 11.8N-m

SPECIAL TOOLS

Valve spring compressor Valve seat cutter, 24.5mm 45° IN-EX Valve seat cutter, 25mm Plane cutter 37.5° EX Valve seat cutter, 22mm Plane cutter 37.5° EX Valve seat cutter, 26mm Plane cutter 63.5° IN/EX Cutter clip Valve guide driver Valve guide reamer

Valve clearance (cold)

Valve rocker arm I.D.

Valve stem O.D.

Valve guide I.D.

Camshaft cam height

Valve seat width

6. CYLINDER HEAD/VALVES

6-3

GRAND DINK 125/15 0

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 oil 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 tensioner

• 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