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7. CYLINDER HEAD/VALVES AGILITY 50

7




7




7-0
7. CYLINDER HEAD/VALVES FILLY LX 50

SERVICE INFORMATION...................... 7-1 CYLINDER HEAD DISASSEMBLY.......7-7
TROUBLESHOOTING ............................ 7-2 CYLINDER HEAD ASSEMBLY .............7-8
CAMSHAFT REMOVAL......................... 7-3 CYLINDER HEAD INSTALLATION .....7-8
CYLINDER HEAD REMOVAL .............. 7-5 CAMSHAFT INSTALLATION................7-9


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 14kg/cm2
Cylinder head warpage 0.05
IN 26.438 26.038
Camshaft cam height
EX 25.807 25.407
Valve rocker arm I.D. IN 10.000-10.015 10.10
EX 10.000-10.015 10.10
Valve rocker arm shaft IN 9.972-9.987 9.91
O.D. EX 9.972-9.987 9.91
Valve seat width IN 1.0 1.8
EX 1.0 1.8
Valve stem O.D. IN 4.975-4.990 4.9
EX 4.955-4.970 4.9
IN 5.000-5.012 5.03
Valve guide I.D.
EX 5.000-5.012 5.03
Valve stem-to-guide IN 0.010-0.037 0.08
clearance EX 0.030-0.057 0.1
Inner 31.1 30.1
Valve spring free
l h Outer 34.35 33.3




7-1
7. CYLINDER HEAD/VALVES AGILITY 50

TORQUE VALUES
Cylinder head nut 1.8~2.2kgf-m Apply engine oil to threads
Valve clearance adjusting nut 0.7~1.1kgf-m Apply engine oil to threads


SPECIAL TOOLS
Valve spring compressor




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




7-2
7. CYLINDER HEAD/VALVES FILLY LX 50
Cylinder Head Cover
CAMSHAFT REMOVAL
Remove the center cover. ( 2-3)
Remove the frame center.
Remove the four cylinder head cover bolts to
remove the cylinder head cover.




Remove the cam chain tensioner sealing bolt Sealing Bolt Bolts
and spring.
Remove the two bolts attaching the cam chain
tensioner and the tensioner.




Turn the flywheel counterclockwise so that Camshaft Gear
the "T" mark on the flywheel aligns with the
index mark on the crankcase to bring the
round hole on the camshaft gear facing up to
the top dead center on the compression
stroke.




Round Hole Punch Marks
Washer Nut
Remove the two cylinder head bolts.
Remove the four cylinder head nuts and
washers.
Remove the camshaft holder.
Diagonally loosen the cylinder head nuts
in 2 or 3 times.




7-3
7. CYLINDER HEAD/VALVES AGILITY 50
Camshaft Holder
Remove the camshaft holder and dowel pins.




Camshaft Dowel Pins
Remove the camshaft gear from the cam
chain and remove the camshaft.




Cam Chain Camshaft Gear

CAMSHAFT INSPECTION
Check each cam lobe for wear or damage.
Measure the cam lobe height.
Service Limits:
IN : 26.038mm replace if below
EX: 25.407mm replace if below




Camshaft Bearings
Check each camshaft bearing for play or
damage. Replace the camshaft assembly
with a new one if the bearings are noisy or
have excessive play.




7-4
7. CYLINDER HEAD/VALVES FILLY LX 50
Rocker Arm Shaft
CAMSHAFT HOLDER DISASSEMBLY
Take out the valve rocker arm shafts using a
5mm bolt.
Remove the valve rocker arms.




5mm Bolt Rocker Arm
Camshaft Holder
CAMSHAFT HOLDER INSPECTION
Inspect the camshaft holder, valve rocker
arms and rocker arm shafts for wear or
damage.

If the valve rocker arm contact surface is
worn, check each cam lobe for wear or
damage.




Rocker Arm Shafts

Measure the I.D. of each valve rocker arm.
Service Limits: IN:10.10mm replace if over
EX:10.10mm replace if over
Measure each rocker arm shaft O.D.
Service Limits: IN: 9.91mm replace if over
EX: 9.91mm replace if over




Intake Manifold
CYLINDER HEAD REMOVAL
Remove the camshaft. ( 7-3)
Remove the carburetor. ( 5-5)
Remove the exhaust muffler. ( 2-5)
Remove the carburetor intake manifold.




7-5
7. CYLINDER HEAD/VALVES AGILITY 50

Remove the cooling fan cover. ( 14-6)
Remove the engine cover bolts and screws.
Separate the engine cover joint claws.




Cylinder Head
Remove the cylinder head.




Bolts
Dowel Pins Cylinder Head Gasket
Remove the dowel pins and cylinder head
gasket.
Remove the cam chain guide.




Cam Chain Guide
7-6
7. CYLINDER HEAD/VALVES FILLY LX 50
Valve Spring Compressor
CYLINDER HEAD DISASSEMBLY
Remove the valve spring cotters, retainers,
springs, spring seats and valve stem seals
using a valve spring compressor.

Be sure to compress the valve springs
with a valve spring compressor.
Mark all disassembled parts to ensure
correct reassembly.

Special
Valve Spring Compressor
Valve Spring Compressor Attachment
Valve Spring Compressor Attachment


Remove carbon deposits from the combustion
chamber.
Clean off any gasket material from the
cylinder head mating surface.

Be careful not to damage the cylinder
head mating surface.




INSPECTION
CYLINDER HEAD
Check the spark plug hole and valve areas for
cracks.
Check the cylinder head for warpage with a
straight edge and feeler gauge.
Service Limit: 0.05mm repair or replace if
over




VALVE SPRING FREE LENGTH
Measure the free length of the inner and outer
valve springs.
Service Limits:
Inner : 30.1mm replace if below
Outer : 33.3mm replace if below




7-7
7. CYLINDER HEAD/VALVES AGILITY 50

VALVE/ VALVE GUIDE
Inspect each valve for bending, burning,
scratches or abnormal stem wear.
Check valve movement in the guide.
Measure each valve stem O.D.
Service Limits: IN : 4.9mm replace if below
EX: 4.9mm replace if below




CYLINDER HEAD ASSEMBLY Valve Spring Compressor

When assembling, a valve spring
compressor must be used.
Install the cotters with the pointed ends
facing down from the upper side of the
cylinder head.
Special
Valve Spring Compressor
Val ve Spring Compressor Attachment

Valve Spring Compressor Attachment
Tap the valve stems gently with a plastic
hammer for 23 times to firmly seat the
cotters.

Be careful not to damage the valves.




CYLINDER HEAD INSTALLATION Dowel Pins Gasket
Install the dowel pins and a new cylinder
head gasket.
Install the cam chain guide.




Cam Chain Guide

7-8
7. CYLINDER HEAD/VALVES FILLY LX 50
Cylinder Head
Install the cylinder head.




CAMSHAFT HOLDER ASSEMBLY Camshaft Holder
First assemble the camshaft holder.
Install the intake and exhaust valve rocker
arms and rocker arm shafts.
When installing the rocker arm shaft,
align the shaft front end with the bolt
hole of the camshaft holder.




Valve Rocker Arm
CAMSHAFT INSTALLATION Cam Chain Camshaft Gear
Turn the flywheel so that the "T" mark on the
flywheel aligns with the index mark on the
crankcase.
Keep the round hole on the camshaft gear
facing up and align the punch marks on the
camshaft gear with the cylinder head surface
(Position the intake and exhaust cam lobes
down.) and install the camshaft onto the
cylinder head.
Install the cam chain over the camshaft gear.


Round Hole Punch Marks
Dowel Pins
Install the dowel pins.




7-9
7. CYLINDER HEAD/VALVES AGILITY 50
Install the camshaft holder, washers and nuts Washer Nut
on the cylinder head.
Tighten the four cylinder head nuts and two
bolts.
Torque: Cylinder head nut: 1.8~2.2kgf-m
Apply engine oil to the threads of the
cylinder head nuts.
Diagonally tighten the cylinder head
nuts in 23 times.



Camshaft Holder
Cam Chain Tensioner Sealing Bolt
CAM CHAIN TENSIONER
INSTALLATION
First install a new cam chain tensioner gasket.
Install the tensioner using the two bolts.
Install the tensioner spring.
Install the O-ring and sealing bolt.

When installing the tensioner, release the
lock pawl and push the push rod all the
way in.

Torque:: 0.45~0.6kgf-m
Lock Pawl Push Rod Spring

O-ring Cylinder Head Cover
Adjust the valve clearance. ( 3-5)
Install a new cylinder head cover O-ring and
install the cylinder head cover.
Be sure to install the O-ring into the
groove properly.

Install and tighten the cylinder head cover
bolts.
Torque:: 0.8~1.2kgf-m




7-10