Over-high temperature of cylinder body

Water pump impeller damaged

Radiator fan broken

Lack of cooling liquid

Temperature sensor damaged

Water pump

Disassemble

Loosen the fastening bolt, remove the crankcase right cover and remove the gasket.

 

 

Remove the water pump gear, loosen the
Fastening bolt and remove the water pump
cover and the gasket.

 

 

Remove the impeller, the water pump shaft,
the water seal assembly, etc.

 

Inspection

Check whether the parts wear.

If badly worn, replace it.

Note:

No damage should be made to the gasket and the box joints in operation.

Installation

Installation should be made in accordance with the reverse order of the removal.

Water pump disassembling

1 Hexagon socket cylinder bolt 2 Gasket 6 3 Water pump cover 4 Water cover seal gasket 5 Pin

6 Impeller 7 Water seal assembly 8 Water pump shaft 9 Pin3*22 10 Water pump gear 11 Gasket

Cylinder head

XI Cylinder Head

Preparatory data 11.1

Fault diagnosis 11.2

Cylinder Head/Valve 11.3

Preparatory Data

Function of cylinder head:

Cylinder head is used to seal cylinder and form a combustion chamber with piston to hold high-temperature and high-pressure fuel gas. It accomplishes air intake and exhausting operation with valve mechanism.

Precautions on Operation

To ensure sealing between cylinder head and cylinder body, there is a great bolt pretension on the cylinder head. Pre-tightening force value 12 NЎ¤m; Locking force value: 30 NЎ¤m.

All the components shall be cleaned before inspection and test, and purged with high-pressure air.

Table of standard values of baseline projects and allowable limit Unit: mm

Item	Standard	Service Limit
Cylinder cover flatness	0.03	0.05
Valve Valve guide	Valve clearance	Intake	0.15-0.2	-
Exhaust	0.2-0.25	-
Valve stem OD	Intake	4.47-4.48	4.455
Exhaust	4.455-4.47	4.448
Valve guide ID	Intake	4.5-4.512	4.53
Exhaust	4.5-4.512	4.53
Clearance between valve stem and valve guide	Intake	0.02-0.042	0.075
Exhaust	0.03-0.057	0.082
Valve race width	Intake	0.9-1	1.6
Exhaust	1-1.1	1.6
Valve spring	Free length	Intake	39.5
Exhaust	39.5
Cam shaft	Fit clearance between the cam shaft and the cylinder head	0.02-0.054	0.08

Fault Diagnosis

Low compression pressure Noisy cylinder head

Improperly adjusted valve clearance Improperly-adjusted valve clearance

Valve burnt or bent Valve spring hurt

Poorly sealed valve race Over-high compression pressure

Air leakage at cylinder head Too much carbon deposited in the combustion chamber

Improperly installed spark plug

 

Cylinder Head

Removal

Loosen the fastening bolt, and
remove the cylinder head cover
(rocker arm, rocker arm shaft)

 

Remove the tensioner, loosen the chain
and remove the can shaft.

 

Cam shaft measurement

 

Measure the size of the cam matching journal

Admission can shaft:

Allowable limit: ¦µ24.957 mm

Exhaust cam shaft:

Allowable limit: ¦µ24.957 mm

Measure the height of the cam shaft

Allowable limit: Intake 36.9 mm

Exhaust 35.9 mm

 

 

Remove the bolt, nut and the cylinder head cover

 

 

Remove the tappet; compress the valve spring with valve spring compressor; remove the valve lock clamp.

Remove the gas distribution adjustment gasket, valve spring, the upper and lower seat of valve spring, valve.

Valve disassembling

 

Inspection

Ruler

Clean carbon deposition on the cylinder cover.

Measure flatness of junction surface of cylinder cover

Allowable limit: 0.05mm.

If flatness of junction surface of cylinder cover exceeds the service limit, put a piece of fine sandpaper on the flat plate and fit the sandpaper with junction surface of cylinder cover; and then push the sandpaper to grind in figure of Ў°8Ў± way.

 

 

Measure the free length of the valve spring.

Vernier caliper

Allowable limit: Spring: 37 mm

 

Measure the outer diameter of the valve stem.

Allowable limit: Intake §¶4.455 mm

Exhaust §¶4.448 mm

 

Check valve guide. Please eliminate the carbon deposition in the valve guide with a reamer before inspection.

 

Attention: Rotate the reamer in clockwise. Please do not rotate the reamer in counterclockwise.

 

 

Measure valve guide ID.

Allowable limit: Intake/Exhaust: §¶4.53mm.

Clearance between valve and valve guide

Allowable limit: Intake Valve: 0.08m.

Exhaust valve: 0.1mm.

Valve Guide Replacement

Attention: When the clearance between valve and valve guide exceeds service limit value, please replace the valve guide. When a valve guide is replaced, surface of valve seat retainer shall be fixed and adjusted.

Put the valve guide into the freezing chamber of refrigerator for one hour to freeze it.

Heat with electric furnace or oven the cylinder head to 100-150Ўж.

Fix the cylinder head and remove the valve guide from upper side of cylinder head with a special valve guide remover.

 

Install a new O ring onto the new valve guide.

Install the valve guide from the top of cylinder head.

Attention: Please do not hurt cylinder head while installing valve guide.

 

When the valve guide is inserted, fix and adjust it with a valve guide reamer.

Attention: When a reamer is used to cut, please apply some amount of cutting lubricant onto it.

Rotate the reamer in clockwise direction.

 

 

Remove carbon deposited in combustion chamber and valve and clean thoroughly intake and exhaust valves.

Inspect width of contact surface of valve seat (width of valve race)

Allowable limit: intake/exhaust: 1.6mm.

 

 

Valve Race Fixing and Adjustment

Remove hackly and ragged parts on the valve race with a 45Ўг angled milling cutter.

Note: Apply a layer of transparent or Prussian blue film onto the valve race so that it can be observed clearly.

 

 

Remove 1/4 of external edge of valve race with a 30Ўг angle milling cutter.

 

 

Remove 1/4 of bottom of valve race with a 70Ўг angle milling cutter.

Remove the milling cutter and check the places processed.

 

Grind and cut valve race with a 45Ўг angle precise milling cutter till it gains a proper width.

1mm

All the dents and ragged parts must be removed.

 

Standard valve race width: Intake: 0.9mm

Exhaust: 1.0mm

 

If contacted place is the higher part of valve, please use a 32Ўг angle plain milling cutter to lower the valve race.

If contacted place is the lower part of valve, please use a 60Ўг angle internal milling cutter to raise the valve race.

Grind and cut valve race with a 45Ўг angle precise milling cutter till it meets the required specification.

After completion of valve race grinding and cutting, please apply some polishing agent on the surface of valve. Polish the valve gently.

 

 

Installation

Install the cylinder head in the reverse order of removal.

 

Attention:

While installing valve spring, the end with short spring links heads combustion chamber.

While installing valve collet, please compress valve spring with a valve spring compressor and install the valve collet.

While installing valve, please apply appropriate amount of engine oil on the surface of valve stem, and then install it into valve guide.

 

Valve clearance adjustment

With a special cylinder head cover for valve clearance adjustment installed, measure the clearance between the cam base circle and tappet with the testing gauge.

Inlet valve: 0.15-0.2mm

Exhaust valve: 0.2-0.25mm

Cylinder Block and Piston