Kymco MO X500 Service Manual - chap 08 (testa valvole)

8. CYLINDER HEAD/VALVES

XCITING 500

8 .

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CYLINDER HEAD/VALVES

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SCHEMATIC DRAWING ------------------------------------------------- 8- 1

SERVICE INFORMATION------------------------------------------------ 8- 2

TROUBLESHOOTING----------------------------------------------------- 8- 3

CYLINDER COMPRESSION TEST ------------------------------------- 8- 4

CYLINDER HEAD COVER----------------------------------------------- 8- 5

CAMSHAFT REMOVAL -------------------------------------------------- 8- 6

ROCKER ARM REMOVAL----------------------------------------------- 8-10

CYLINDER HEAD REMOVAL ------------------------------------------ 8-11

CYLINDER HEAD INSTALLATION ----------------------------------- 8-16

ROCKER ARM INSTALLATION---------------------------------------- 8-18

CAMSHAFT INSTALLATION ------------------------------------------- 8-19

8

CYLINDER HEAD COVER INSTALLATION ------------------------ 8-23

8-0

8. CYLINDER HEAD/VALVES

SCHEMATIC DRAWING

XCITING 500

8-1

8. CYLINDER HEAD/VALVES

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XCITING 500

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

Ite

Valve clearance (cold)

Cylinder head compression pressure 13 kg/cm2 (185 psi, 1300 kPa) ⎯

Cylinder head warpage

Camshaft cam height

Valve rocker arm I.D.

Valve rocker arm shaft IN 9.975 (0.399)～9.99 (0.3996
O.D. EX 9.975 (0.399)～9.99 (0.3996

Valve stem O.D.

Valve guide I.D.

Valve stem-to-guide IN 0.01 (0.004)～0.037 (0.0015
clearance EX 0.03 (0.0012)～0.057 (0.0023

TORQUE VALUES

Cylinder head bolt (13) 13 N•m (1.3 kgf•m, 9 lbf•ft) Apply engine oil to threads
Cylinder head bolt (1 – 4) 48 N•m (4.8 kgf•m, 35 lbf•ft) Apply engine oil to threads

IN 0.1 mm (0.004 in

EX 0.1 mm (0.004 in

IN 37.2614 (1.4905

EX 37.0084 (1.4803

IN 10 (0.4)～10.015 (0.4006

EX 10 (0.4)～10.015 (0.4006

IN 4.975 (0.199)～4.99 (0.1996

EX 4.955 (0.1982)～4.97 (0.1988

IN 5 (0.2)～5.015 (0.2006

EX 5 (0.2)～5.015 (0.2006

Standar

0.05 (0.002

37.11 (1.4844

36.86 (1.4744

10.1 (0.404

10.1 (0.404

9.9 (0.396

9.9 (0.396

4.925 (0.197

4.915 (0.1966

5.03 (0.2012

5.03 (0.2012

0.08 (0.0032

0.1

Unit: mm (in)

Service Limit

0.004

Cylinder head bolt (5 – 12) 23 N•m (2.3 kgf•m, 17 lbf•ft) Apply engine oil to threads
Cylinder head cover bolt 10 N•m (1 kgf•m, 7 lbf•ft)
Cylinder head cover bolt 10 N•m (1 kgf•m, 7 lbf•ft)
Breather separator bolt 13 N•m (1.3 kgf•m, 9 lbf•ft)
Cam chain tensioner bolt 12 N•m (1.2 kgf•m, 9 lbf•ft)
Tensioner pivot bolt 10 N•m (1 kgf•m, 7 lbf•ft)
Rocker arm shaft 45 N•m (4.5 kgf•m, 32 lbf•ft)

SPECIAL TOOLS

Valve spring compressor E040

8-2

8. CYLINDER HEAD/VALVES

XCITING 500

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

8-3

8. CYLINDER HEAD/VALVES

CYLINDER COMPRESSION TEST

Warm up the engine to normal operating
temperature.
Stop the engine and remove the spark plug
cap and remove the spark plug (page 3-7).

XCITING 500

Park Plug Cap

Install a compression gauge into the spark
plug hole.

Open the throttle all the way and crank the
engine with the starter motor until the gauge
reading stops rising.

The maximum reading is usually reached 4 –
7 seconds.

＊

To avoid discharging the battery, do not
operate the starter motor for more than
seven seconds.

Compression pressure:

13 kg/cm2 (185 psi, 1300 kPa)

Low compression can be caused by:

 Blown cylinder head gasket
 Improper valve adjustment
 Valve leakage
 Worn piston ring or cylinder

Compression Gauge

High compression can be caused by:

 Carbon deposits in combustion chamber or

on piston head

8-4

8. CYLINDER HEAD/VALVES

CYLINDER HEAD COVER

DISASSEMBLY

Remove the floorboard (page 2-6).
Remove the spark plug caps (page 8-4)
Disconnect the crankcase breather hose from
the cylinder head cover (page 7-3).

Remove the four bolts and head cover.

Remove the cylinder head cover packing.

XCITING 500

Bolts

Cylinder Head Cover

Cylinder Head Cover Packing

Remove the bolts and breather separator.

8-5

Bolts

8. CYLINDER HEAD/VALVES

t

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Remove the gasket.

ASSEMBLY

Assembly is in the reverse order of
disassembly.

Torque:
Breather separator bolt:

13 N•m (1.3 kgf•m, 9 lbf•ft)

CAMSHAFT REMOVAL

Remove the cylinder head cover (page 8-5).
Turn the crankshaft clockwise and align the

“T” mark on the flywheel with the index
mark on the right crankcase cover (page 3-9).

XCITING 500

Gaske

Bolt Washe

Remove the cam chain tensioner lifter sealing
bolt, spring and sealing washer.

Remove the two bolts, cam chain tensioner
and gasket.

Spring

Cam Chain Tensioner/Gaske

Bolts

8-6

8. CYLINDER HEAD/VALVES

Remove the two bolts and cam chain guide.

XCITING 500

Bolts

Cam Chain Guide

Loosen and remove the twelve camshaft
holder bolts in a crisscross pattern in several
steps, then remove the camshaft holders.

＊

Suspend the cam chain with a piece of
wire to prevent the chain from falling
into the crankcase.

Remove the camshafts

Camshaft Holders Bolts

Camshafts

8-7