LC2V80FD

Maintenance Manual

LONCIN MOTOR CO., LTD.

SAFETY INFORMATION
Before operating and maintaining the engine,
machine is stopped for a moment, it would be
please carefully read and understand the
hot. Be careful not to touch the burning silencer.
Maintenance Manual. To use the machine safely
Prior to maintenance, the engine shall be placed
and efficiently, you must conduct proper
indoor and cooled down.
maintenance and operation to the machine.
● To prevent fire, when the engine is working,
The following identifications throughout the
the distance between the engine and the wall
Manual may give
ive prompts to operators and
shall be kept at least 1 m. Inflammables must be
maintainers as well as illustrate matters that
away from the engine.
cause dangers.

The identification reminds you to Carbon Monoxide Poisoning

note that it may cause severe personal injury or
death which is imperative. ● The exhaust contains poisonous carbon
monoxide. Avoid inhaling the exhaust.
The identification reminds you to
● Don’t use indoors.
note that it may cause
use severe personal injury or
death or improper operation.
● Don’t operate the engine in the closed
garage or enclosed area.
This identification reminds you to
note that it may cause personal injury or property General Precautions
damage or improper operation.
● Carefully read the Maintenance Manual, gget
Be vigilant to fuel oil, exhaust emissions and familiar with all the control mechanisms and the
moving parts to avoid severe personal
perso injury or
correct using and maintenance & installing
death.
method of the machine and master the operating
Add fuel carefully! method of stopping and fast separating the
machine.
● Gasoline is inflammable. Please add the
● When you feel fatigue, have discomfort or
fuel oil in the outdoor, well-ventilated
ventilated area after
have a drink, please
se don’t operate the engine;
the engine is stopped.
otherwise, it may cause severe injury.
● It is prohibited to smoke when adding
● Children and people who don’t read the
gasoline and be away from flame and spark.
Manual or without training are prohibited to use
● It is prohibited to start the engine before the
gasoline splashed area is dry. the engine.
● Don’t repair the machine without mastering
Heat Exhaust the method of engine repair.
● Don’t refitt the machine or change its
● The temperature of silencer can be very
structure. Once the machine loses its balance, it
high during the operation of engine; even if the
may easily cause damages and injury incidents.
Contents

Part I Technical Specifications

1-1 Introduction of engine....................................................................................................................................1

1-2 Technical parameters .....................................................................................................................................3

1-3 Model installation dimensional drawing........................................................................................................4

1-4 P.T.O dimensional drawing ...........................................................................................................................7

1-5 Electric wiring diagram .................................................................................................................................9

Part II Repair Instructions

2-1 Maintenance precautions .............................................................................................................................10

2-2 Marking position of machine No. ................................................................................................................11

2-3 Maintenance standards.................................................................................................................................12

2-4 Torque parameters of fasteners ....................................................................................................................13

Part III Maintenance

3-1 Maintenance schedule ..................................................................................................................................15

3-2 Change engine oil ........................................................................................................................................16

3-3 Maintenance of air filter ..............................................................................................................................18

3-4 Maintenance of silencer ...............................................................................................................................19

3-5 Maintenance of spark plug...........................................................................................................................20

3-6 Adjustment of valve clearance.....................................................................................................................21

3-7 Adjustment of idle speed .............................................................................................................................21

3-8 Adjustment of speed regulator .....................................................................................................................22

3-9 Storage of engine .........................................................................................................................................23

Part IV Faults Diagnosis

4-1 Difficulty of engine in starting .....................................................................................................................25

4-2 Underpower of engine ..................................................................................................................................26

4-3 Rotating speed instability of engine .............................................................................................................27

4-4 Abnormal exhaust colors of engine ..............................................................................................................28

4-5 Engine is easily to be flameout ....................................................................................................................29

4-6 Engine has no high speed .............................................................................................................................29

4-7 Overheat of engine .......................................................................................................................................30

4-8 Abnormal noises of engine ...........................................................................................................................31

4-9 Fault of electric starting system ...................................................................................................................32

Contents
4-10 Check the cylinder pressure .......................................................................................................................33

4-11 Detection of spark ......................................................................................................................................33

Part V Disassembly & Repair

5-1 Precautions on disassembly/assembly .........................................................................................................34

5-1-1 Disassembly ..............................................................................................................................................34

5-1-2 Assembly ..................................................................................................................................................34

5-2 Disassembly and maintenance of engine......................................................................................................35

5-2-1 Air filter ....................................................................................................................................................35

5-2-2 Silencer .....................................................................................................................................................36

5-2-3 Fan cover - starting control switch............................................................................................................37

5-2-4 Carburetor .................................................................................................................................................40

5-2-5 Speed-regulating mechanism ....................................................................................................................43

5-2-6 Flywheel and ignition coil ........................................................................................................................44

5-2-7 Cylinder head and valve ...........................................................................................................................47

5-2-8 Secondary oil filter, breather slot and air guide sleeve.............................................................................52

5-2-9 Crankcase, crankshaft and piston .............................................................................................................54

Part I Technical Specifications

1-1 Introduction of engine

Silencer Air filter

Fuel pump

Choke-valve
handles

Spark plug cap

Engine switch

Secondary oil filter

Throttle handle

Oil drain bolt

Oil condenser

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Part I Technical Specifications

Air filter - protect the engine through filtering dusts and impurities in the air.
Spark plug - input high voltage at ignition coil to the engine combustor, generate spark through
air discharge between electrodes and introduce combustion of mixed gases.
Silencer - a device to prevent the transmission of engine sound and reduce the noise of exhaust
system.
Fuel filter - filter impurities in the fuel through oil pipes between fuel tank and carburetor.
Oil condenser - pump the engine oil into it through the oil pump and enter the lubricating main oil
gallery after it is cooled down by the cooling fin.
Secondary oil filter - oil passes it to filter impurities and then enters the lubricating main oil
gallery.
Choke-valve handle - cold start the engine and close the choke valve, the carburetor would supply
concentrated mixed gas, which makes the engine to be easily started. After preheating the engine,
fully open the choke-valve handle.
Engine switch - before starting the engine, turn the switch to “ON” position; the engine can be
shut down when turning the switch to “OFF” position.
Throttle handle - turning throttle handle may adjust the rotating speed of the engine to achieve
the power and rotating speed expected.
Oil drain plug - swinging out drain plug may drain all the oil in the engine out so as to replace the
oil.

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Part I Technical Specifications

1-2 Technical parameters

Single-engine Power Unit Power

Double-cylinder, four-stroke-cycle, forced-air cooling and overhead

Type of Engine
valve
Air displacement
764ml（80mmX76mm）
(diameter of cylinder × stroke)
Maximum power
19
(kW/3600rpm)
Maximum torque (N·m)
52/2800
Corresponding rotating speed (rpm)
Fuel consumption rate
≤ 350
(g/kW·h)
Idle speed
1,800±150
(rpm)

Speed fluctuation rate ≤ 10%

Compression ratio 8.7:1

Starting mode Electronic start

Direction of rotation Anticlockwise (output terminal)

Inlet valve 0.10 ~ 0.15

Valve clearance (mm)
Exhaust valve 0.15 ~ 0.20

Spark plug RC12YC

Spark plug gap (mm) 0.7 ~ 0.8

Ignition mode Transistorized magneto ignition

Type of air filter Double filter cartridge

External dimensions (mm)

507×502×690 507×502×500
L×W×H

Net weight (kg) 50 49

The rated power of the engine indicated in the Manual is the net output power (net power) at 3,600 rpm of an
engine under the production status measured in accordance with SAE J1349. For mass production engines, the
value may vary.
The actual power of engine installed on the terminal may vary in output, which depends on several factors
including the rotating speed of engine during practical use, environmental conditions, maintenance and other
variants.

-3-
Part I Technical Specifications

1-3 Model installation dimensional drawing

Unit power

-4-
Part I Technical Specifications

Single-engine power

-5-
Part I Technical Specifications

Crankcase cover interface dimensions

Mounting size of base

-6-
Part I Technical Specifications

1-4 P.T.O dimensional drawing

A 轴/Type A

B轴/Type B
-7-
Part I Technical Specifications

C轴/Type C

-8-
Part I Technical Specifications

1-5 Electric wiring diagram

-9-
Part II Repair Instructions

2-1 Maintenance Precautions 5. Parts shall be cleaned after being dismantled and
shall be coated with oil on the sliding surface
1. Use pure LONCIN parts or the specified parts and
during assembly.
lubricating oil. Parts not meeting LONCIN’s
design specifications may damage the device or
the engine.

6. Fastening places and action status must be checked

after the assembly.

2. Operations requiring special tools must be

completed with special tools and corresponding
devices.

7. The engine shall be shut down when it is under

check and maintenance. Operation shall be done
after the engine is completely cooled down.
Operation in high temperature of the engine may
cause accidents such as burning injuries.

3. The washer, gasket, O-ring,

ring, oil seal, etc. shall be
replaced after being dismantled.

8. After maintenance, if it needs to carry out running

4. When fastening bolts, nuts and screws, fasten test on the operation site, please note full
them in an order from larger diameter to smaller ventilation. In addition, fire must be prohibited
one and from inside to outside in a crossing way near inflammables such as fuel an
and grease.
to the specified torque.

- 10 -
Part II Repair Instructions
Follow up the guidance indicated by the signs below:

Coat oil at the Operate with Coat grease at the

indicated special tools. indicated
position. position.
○×○(○): the mode, length and quantity of flange bolt.
P.: the page shall be referred to.

2-2 Marking position of machine No.

Machine No. is marked on the crankcase as shown in the figure below. When LONCIN dealers
require correct parts during maintenance, the machine number is used to check the engine or to order
parts.

Marking position
of machine No.

Engine No.:

TXXXXX XX XX XXXXXXX

Serial no.

Production month

Production year

Development order no.

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Part II Repair Instructions
2-3 Maintenance standards

Unspecified unit: mm
LC2V80FD
Parts Item
Standard Maintenance limit
2
Engine Compression pressure (kgf/cm )* 11-13 －
Air cylinder Inner diameter of cylinder liner 80-80.01 80.15
Outer diameter of skirt 79.965-79.975 79.755
Clearance to the air cylinder 0.025～0.045 0.255
Piston
Inner diameter of piston pin hole 17.002～17.008 17.12
Clearance between the piston pin and
0.004～0.016 0.029
piston pin hole
Piston pin Outer diameter 16.992～16.998 16.9
Clearance to the side of the piston ring
0.02～0.06 0.11
(gas ring 1 / gas ring 2)
Clearance to the side of the piston ring
0.03～0.08 0.15
oil ring
Clearance to the end of the piston ring
0.20～0.40 0.7
gas ring 1
Clearance to the end of the piston ring
Piston ring 0.30～0.50 0.8
gas ring 2
Clearance to the end of the piston ring
0.20～0.70 1.0
oil ring
Width of ring (gas ring 1) 2.90 2.77
Width of ring (gas ring 2) 3.30 3.17
Width of ring (oil ring) 2.60 2.07
Inner diameter of the small end 17.006～17.017 17.05
Inner diameter of the big end 40.015～40.025 40.065
Connecting rod
Oil-film clearance of the big end 0.024-0.059 0.115
Side clearance of the big end 0.203～0.403 1.0
Outer diameter of the crankshaft journal
Crankshaft 39.966～39.991 39.906
(big end of the connecting rod)
Valve clearance (cold) Inlet 0.10~0.15 －
Valve clearance (cold) Exhaust 0. 15~0.20 －
Valve
Outer diameter of valve stem Inlet 6.565～6.58 6.438
Outer diameter of valve stem Exhaust 6.545～6.56 6.435
Inner diameter of valve guide Inlet &
6.6～6.615 6.672
exhaust
Clearance between valve stem and
Valve guide 0.02～0.05 0.15
valve guide Inlet
Clearance between the valve stem and
0.04～0.07 0.17
valve guide Exhaust
Valve seat Contact width of valve seat 0.7～0.8 2.0
Valve spring Free length 39.5～40.5 39
Cam height Inlet 29.95～30.05 29.75
Camshaft
Cam height Exhaust 29.95～30.05 29.75

- 12 -
Part II Repair Instructions
Outer diameter (bearing position) 15.966～15.984 15.916
Crankcase cover Inner diameter of camshaft hole 16～16.018 16.068
Spark plug Electrode clearance 0.7-0.8 －
Spark plug cap Resistance 10kΩ －
Resistance value Primary side 1-1.4Ω －
Ignition coil Resistance value Secondary side 6.2-7.6Ω －
Clearance to the flywheel 0.3～0.4 －

2-4 Torque parameters of fasteners

(1) Torque parameters of parts
Fastening Item Specification of Thread Fastening Torque (N.m)

Fastening bolt of connecting rod M6×1 11-13

Fastening bolt of cylinder head M10×1.25 50-55

Fastening bolt of flywheel M12×1.25 80-100

Fastening bolt of crankcase cover M8 × 1.25 25-30

Seal screw plug (crankcase-body oil
M14 × 1.5 30-35
drain plug)
Valve adjusting bolt M8×1.25 28-32

Valve lock nut M6×0.75 12-16

Fastening bolt of cylinder-head-cover M6 × 1 8-12
Fastening bolt of breather slot cover
M6 × 1 8-12
plate
Oil pipe connection of radiator M10 × 1 20-25

Mounting bolt for secondary oil filter M20 × 1.5 40-45

Secondary oil filter 3/4-16UNF 10-13

Fastening nut of speed-regulating
M6 × 1 8-10
support
Fastening bolt of starting motor M8 × 1.25 22-28

Spark plug 25-30

Note: for unspecified bolts and nuts in the above mentioned table, please refer to standard torques.

- 13 -
Part II Repair Instructions

(2) Standard torque parameters

Fastening Parts Specification of Thread Torque (N.m)

5 mm Bolt and nut 4-7

6 mm Bolt and nut 8-12

Bolt and nut 8 mm Bolt and nut 20-28

10 mm Bolt and nut 35-40

12 mm Bolt and nut 50-60

- 14 -
Part III Maintenance

3-1 Table of maintenance periods

20 H or the 50 H or 100 H or 300 H or

Time
Periodic Maintenance Schedule first Month Every 3 Every 6 Every
of Use
of Initial Use Months Months Year

Check the oil

○
level
Engine oil
Replacement ○ ○
Secondary oil
Replacement ○(2) 200 h
filter
Check ○

Air filter Clear ○(1)

Replacement ○(3)

Fuel filter Replacement ○(1)

Position of
battery Check ○
electrolyte
Check and
adjust the ○(2)
Spark plug clearance
Replacement ○
Check and
Valve
adjust the ○(2)
clearance clearance
Oil pipe Replacement Every 2 years (2)

○ Maintenance matters
(1) Maintenance intervals shall be shortened when it is used in a place full of dusts.
(2) Unless users have professional repair tools and maintenance skills, or these projects shall be
assisted and maintained by franchised dealers of LONCIN.
(3) Only replace foam and paper filter cartridge
Under circumstances of frequent use, long-term use can only be guaranteed through maintenance
with correct intervals specified above.

- 15 -
Part III Maintenance

3-2 Change engine oil

Note: drain engine oil when the machine is stopped but not cooled down so as to guarantee the fast and
thorough exhaust of the oil.
The engine oil of gasoline is the main factor that affects the
performance and life of gasoline. Suggest not using engine
oil containing additive substance and two-stroke engine oil
as they are lack of lubrication, which may shorten the service
life of the gasoline.
Oil drain plug
When checking the engine oil, shut down the machine and
place it on a horizontal plane.
Capacity for engine oil: Gasket
Without replacement of secondary oil filter: 1.6 L
With replacement of secondary oil filter: 1.8 L

To make the engine achieve its ideal operating effect, it is

suggested to use the qualified and dedicated engine oil of
LONCIN.

Recommended engine oil:

4-stroke gasoline engine oil.
API-classified SE, SF or equivalent to SG grade’s SAE 10W-30.

Ambient
You can use engine oil in other viscosity when the local temperature
temperature is within the scope as shown in the figure.

Check steps:
1) Remove the oil level gauge and wipe out the engine oil.
2) Insert the oil level gauge into the oil-filling hole but do
Oil level
not screw it up, then check the oil level. gauge
Maximum
3) If the oil level is too low, fill the recommended engine oil level

till it reaches the upper limits indicated by the oil level gauge. Minimum
oil level
4) Re-install the oil level gauge. Oil plug

Oil filling
port

- 16 -
Part III Maintenance

The waste oil contains hazardous substances which may cause

caus skin cancer for long-term
term exposure to the waste oil.
After exposing to the waste oil, please thoroughly clean your hands with soap and clear water as soon as possible.
Please dispose the waste oil and container after use in an
a environmental protection manner. We suggest you
putting the waste oil into a sealed container and then send it to the local service station or to the waste oil
recycling center.

Bear in mind: don’t throw it into the garbage dump or pour it onto the ground.

- 17 -
Part III Maintenance

3-3 Maintenance of air filter

Air inflow will be affected and the power of engine will be reduced after the filter element of the air filter gets
dirty. If the operation area is full of dust, the maintenance shall be conducted more frequently.
Caution No filter cartridge or use of damaged filter cartridge may cause dusts to enter the engine and
then cause the rapid erosion of the engine.

Dual-filter cartridge air filter

1) Open the clip and remove the air filter cover.
2) Check the filter cartridge and replace it if it is damaged. Paper filter cartridge can usually replaced at the
interval of maintenance schedule.
Clean the paper filter cartridge:
Slightly tap the filter cartridge for several times and then blow from inside to outside with the compressed air
of the pressure not exceeding 207 KPa. Never brush the paper filter cartridge with brushes; otherwise, it may
block the air vent hole.

Air filter cover

Filter cartridge

Filter cartridge

Air filter cover

Filter cartridge

3) Clean the base, housing lid, cushion, etc. of the air filter and prevent dusts entering the air inlet to the
carburetor.
4) Install the filter cartridge well.
5) Install the air filter cover and fasten the clip.

- 18 -
Part III Maintenance

3-4 Maintenance of silencer

During the long-term
term use of silencer, it may cause
carbon deposition and bring about severe influence
to the exhaust system. To make the exhaust system
work better, generally, we will remove the carbon
deposition of the silencer.
When removing the internal carbon deposition inside
the silencer, use a hammer to slightly tap it and blow
it with the compressed air.

Please refer to the “Maintenance Schedule” for the

cleaning of spark canceller. Remove the mesh of spark
canceller after the electric
lectric generator is cooled down.
Sweep away the carbon deposition accumulated on the mesh
with wire brush. Re-install
install the spark canceller and fasten screws.

Caution

Don’t clean it with iron wire, or it may cause abscission

of acoustic material and so reduce the sound deadening
performance.
Sealing gasket of the silencer must not be used repeatedly.
Replace a new one if the silencer is accumulated with water
drops or severe erosion and cause increased noise.

The silencer would become hot and please place the gasoline
engine in a place that the passersby and children cannot reach.

When the gasoline engine is working, don’t place any

inflammables close to the air vent.

- 19 -
Part III Maintenance

3-5 Maintenance of spark plug

Recommended spark-plug types: RC12YC or equivalent

spark plugs.
The replacement of spark plug has the following
advantages: Spark
plug cap
Guarantee the continuous spark; start with more
reliability; better fuel conservation

Note
The use of spark plug with incorrect models and
heat values may reduce the engine performance or
damage the engine.
1. Take off the spark plug cap and remove dusts around

the spark plug.

2. Dismantle the spark plug with socket wrench for spark plug.
Side
electrode
3. Check if the electrode of the spark plug is excessive worn, 0.7-0.8 mm Steel wire brush

and if the insulator is cracked or if there is too much carbon

deposition.

If it can be continuously used, use the steel wire brush to

remove impurities such as carbon deposition.

4. Measure the electrode clearance of the spark plug with a

feeler gauge and the correct clearance shall be 0.7 ~ 0.8 mm.

If it requires adjustment, slightly tap (when the clearance

is huge) or pry the electrode with a slotted screwdriver (when

the clearance is small).

5. Impact the gasket tightly with the socket spanner of spark plug.

When re-installing a used spark plug, screw 1/8-1/4 circle

more after the gasket is impacted. When installing new spark

plug, screw 1/2 circle more after the gasket is impacted.

Note
Too loose spark plug may be overheat and damage the engine. Fastening too tight may cause the
- 20 -
Part III Maintenance

spark plug mounting thread disorder inside the engine.

6. Install the spark plug cap onto the spark plug. Thickness gauge

3-6 Adjustment of valve clearance

The check and adjustment of valve clearance must be

conducted when the engine is cold.

Seen from the output end of the engine, firstly adjust

the valve clearance of the left cylinder, then rotate

anticlockwise the crankshaft to 270° before adjusting

Valve adjusting nut
the right cylinder.

1. Remove the cylinder-head cover and place the piston

on the upper dead center of compression stroke,
The two valves are both closed.
2. Measure the clearance between the rocker arm and
valve stem with a thickness gauge.
Inlet valve: 0.10 ~ 0.15 mm
Valve rocker arms
Exhaust valve: 0.15 ~ 0.20 mm

3. To adjust the valve, the valve-adjusting nut shall be

fixed and loosen the valve while fastening the nut.
4. Rotate the valve-adjusting nut to obtain the specified clearance.
5. Re-check the valve clearance and re-adjust it if necessary.
6. Install the cylinder-head cover.

3-7 Adjustment of idle speed

 Mechanical speed regulating engine High speed
1. Start the engine outdoors to warm it for a while.
2. Place the control level to the minimum rotation speed
Low speed
location.
3. Adjust the idle adjusting screw with tools to control the
rotation speed within the scope of standard idle speed.

 Electronic adjustable speed engine

1. Start the engine outdoors to warm it for a while.
2. Connect idle switch

- 21 -
Part III Maintenance

Standard engine idle rotation speed: 1,800±150 rpm

3-8 Adjustment of speed regulator

 Mechanical speed regulating engine Throttle pull
rod
Fuel control assy.

Speed-regulating spring

Accelerator, rope
Throttle control
handles

Speed-regulating support Speed-regulating arm

1. Loosen the fastening nut of speed-regulating arm.

2. Rotate the speed-regulating support till the valve is fully opened and fix it at the location.

3. Rotate the speed-regulating arm anticlockwise till the end (i.e. position that the speed regulator is fully closed)
and then fasten the nut.

4. Check if activities of the speed-regulating support and valve are flexible.

5. Start the engine to warm it till it achieve the normal operating temperature, and then adjust it to the specified
working rotation speed.
 Electronic adjustable speed engine

Carburetor with step motor Electronic speed controller

1. Determines the program commands in the control module

- 22 -
Part III Maintenance

2. The control module controls the stepper motor

3. Stepper motor controls throttle opening of carburetor
4. Ensure fixed speed, high speed and low speed

Controller Pass procedure Step motor Control Throttle opening Fixed speed

3-9 Storage of engine

After it is shut down, cool the engine down for at least half an hour prior to cleaning. Clean the outer surface,
repair the damaged baking finish and coat thin rust resisting oil on areas that are possible rust.

Caution

Washing water with high pressure can enter the air filter and silencer and even enter the cylinder along with the air
passage and cause corrosion and damage.
Water splashing on the hot engine may wreak damage. Therefore, cleaning must be done after the engine is cooled
down.

1) Place a suitable container for containing gasoline under the carburetor (under the overflow pipe).
2) Loosen the oil drain bolt of carburetor, drain the oil in the carburetor to the container for containing gasoline
and fasten the oil drain bolt of carburetor after completing oil drain.

Oil drain plug

Overflow pipe

3) Replace engine oil when use it again.

4) Remove the two spark plugs.
5) Pour into a spoon of (5-10 ml) clear engine oil into the cylinder head.
6) Rotate the engine for several circles to scatter the engine oil spread throughout the cylinder head.

- 23 -
Part III Maintenance

7) Re-install the spark plug.

8) Rotate the engine slowly till you feel the resistance. The inlet and exhaust valves are both in the closed status,
which prevent moisture entering the cylinder head.
9) Cover an anti-dust coating to the engine and place it in a ventilated dry place.
During the storage, charge the battery every month. It is benefit for prolonging the service life of the battery.

- 24 -
Part IV Faults Diagnosis

4-1 Difficulty of engine in starting

Excessive engine oil
(Stop for several minutes before restarting)

Insufficient fuel
(Add fuel oil into the fuel tank)
Fuel system
Fuel filter screen blocked
(Clean fuel filter screen)

Fault or improper adjustment of carburetor

(Refer to Section 5-2-4)

Air cleaner dirty

(Clean or replace)

Fault of spark plug

(Refer to Section 3-5)

Improper clearance of spark plug

(Refer to Section 3-5
Difficulty in Improper clearance between ignition coil and flywheel
starting Ignition system
(Refer to Section 5-2-6)
Fault of ignition coil
(Refer to Section 5-2-6)
Fault of ignition switch
(Replace ignition switch)

Insufficient magnetic density

(Replace flywheel)

Improper clearance of valve

(Refer to Section 3-6)
Gasket of cylinder head damaged
(Refer to Section 5-2-7)

Loosened cylinder bolt

Compression (Refer to Section 5-2-7)
system
Seal of valve not good
(Refer to Section 5-2-7)

Excessive wear of cylinder/piston/piston ring

(Refer to Section 5-2-9)
Excessive wear of camshaft
(Refer to Section 5-2-9)

- 25 -
Part IV Faults Diagnosis

4-2 Underpower of engine

Poor fuel quality

(Use new fuel of designated quality)

Fuel filter blocked

Fuel system (Clean fuel filter)

Fault or improper adjustment of carburetor

(Refer to Section 5-2-4)

Choke valve not fully opened

(Open it to the maximum)

Air filter dirty

(Clean air filter)

Spark plug defective

(Refer to Section 3-5)
Ignition system
Wrong ignition time
(Adjust ignition time)

Excessive wear of cylinder/piston/piston ring

(Refer to Section 5-2-9)
Underpower
Compression Improper valve clearance
system (Refer to Section 3-6)

Seal of valve seat not good

(Refer to Section 5-2-7)

Cooling fan too dirty

(Clean)
Cylinder cooling fin too dirty
(Clean)

Others Silencer blocked

(Refer to Section 3-4)

Improper regulation of speed-regulating system

(Refer to Section 3-8)

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Part IV Faults Diagnosis

4-3 Rotating speed instability of engine

Fuel is insufficient/of poor quality/polluted

(Use new fuel oil of specified quality)
Fuel filter blocked
Fuel system
(Clean fuel filter)

Carburetor blocked
(Refer to Section 5-2-4)

Spark plug blocked

Rotational
(Refer to Section 3-5)
speed Ignition system
instability
Loosened ignition circuit
(Refer to Section 5-2-6)

Improper regulation of speed-regulating system

(Refer to Section 3-8)
Speed-regulating
system
Dysfunction of timing gear
(Replace)

- 27 -
Part IV Faults Diagnosis

4-4 Abnormal exhaust colors of engine

Air filter excessively dirty

(Clean air filter)

Black Fault of carburetor

(Refer to Section 5-2-4)

Overloaded
(Alleviate load)

Low temperature of engine

Abnormal (Normal starting)

exhaust color White

Water contained in fuel

(Use new fuel oil of specified quality)

Engine oil contained in fuel

(Use new fuel oil of specified quality)

Excessive wear of cylinder/piston/piston ring

(Refer to Section 5-2-9)

Blue

Too much engine oil added

(Refer to Section 3-2)

Fault of cylinder head

(Refer to Section 5-2-7)

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Part IV Faults Diagnosis

4-5 Engine is easily to be flameout

Spark plug dirty or wet

(Refer to Section 3-5)

Fuel level of carburetor too high

Engine is
(Adjust the height of the float of the carburetor)
easily to be
flameout
Improper idle speed adjustment

(Refer to Section 3-7)

Insulator of carburetor damaged

(Refer to Section 5-2-4)

Burning loss of electron magnetic valve of carburetor

4-6 Engine has no high speed (Replace electron magnetic valve of carburetor)

Spark plug faulty or dirty

(Refer to Section 3-5)

Silencer blocked

(Refer to Section 3-4)

Fuel oil is of poor quality/polluted

(Add new fuel oil)

Engine has
no high
Overheat of engine
speed
(Clean cooling fan and radiating fin)
Improper regulation of speed regulator
(Refer to Section 3-8)
Overloaded
(Alleviate load)

Fault of carburetor
(Clean and regulate carburetor)

Air filter too dirty

(Clean air filter)

- 29 -
Part IV Faults Diagnosis

4-7 Overheat of engine

Wrong ignition time

(Adjust ignition time)

Engine oil insufficient or polluted

(Add or replace engine oil)

Silencer blocked

(Refer to Section 3-4)

Overheat of
engine Ring flutter of cylinder and crankcase due to
failure of piston ring causing
(Replace worn parts)
Too high rotational speed of gasoline engine
(Repair speed-regulating system or replace speed-regulating gear)

Overloaded
(Alleviate load)

Air passage blocked with impurties

(Clean radiating fin)

Cooling fan broken

(Replace blade wheel)

- 30 -
Part IV Faults Diagnosis

4-8 Abnormal noises of engine

Wear of piston and piston ring

(Replace piston and piston ring)

Wear of connecting-rod, piston pin and pin hole

(Replace worn parts)
Rattle
Wear of crankshaft bearing
(Replace wore parts)

Breakage of piston ring

(Replace piston ring)

Excessive carbon deposition in combustor

(Remove carbon deposition)

Clearance of spark plug electrode too small

(Refer to Section 3-5)
Detonation with
Abnormal Overheat of engine
metallic sound
noises of engine
(Refer to Section 4-7)

Wrong fuel grades

(Replace fuel)

Serious fuel rich of engine

(Check and adjust carburetor)

Improper adjustment of valve clearance/wear of

relevant parts
(Adjust valve clearance and replace worn parts)
Other abnormal
noises Loose connection between flywheel and crankshaft
(Replace connecting parts and re-install)

Bearing wear inside crankcase

(Replace bearing)

- 31 -
Part IV Faults Diagnosis

4-9 Fault of electric starting system

Battery fault
(Charge or replace)
Short circuit or broken circuit of lead wire or
No click sound connecting plug
(Repair or replace)

Fuse burn-out
(Replace)
Dose the
electric relay Fault of engine switch
(switch) have
(Repair or replace)
click sound?

Undervoltage of battery
(Charge or replace)
Have click Short circuit or broken circuit of lead wire or
sound connecting plug
(Repair or replace)

Fault of starting engine

(Repair or replace)

Fault of battery
(Replace battery)

Short circuit or broken circuit of lead wire or connecting plug

Storage battery
cannot be (Repair or replace)
charged
Fault of charging coil

(Repair or replace)

Fault of magneto rotor

(Repair or replace)

- 32 -
Part IV Faults Diagnosis

4-10 Check the cylinder pressure

1) Remove the spark plug cap and spark plug.
2) Install the pressure gauge onto the spark plug hole
3) Start the engine for several times to measure the compression
pressure.
Pressure
Cylinder
11-13 Kgf/cm2 gauge
pressure

4-11 Detection of spark Spark

1) Remove the spark plug plug

2) Install the spark plug onto the spark plug cap.

3) Ground the (-) electrode (thread part) of spark plug and start the
engine to check the spark.

Warning
It is prohibited to touch the spark plug wire with wet hands during the test.
When touching the high-voltage line with wet hands, starting engine may cause high voltage, which is very
dangerous.
The falling fuel oil may ignite around the spark plug. Remove the fuel oil and then check. Stay away from the
spark plug hole when testing.

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Chapter V Disassembly & Repair

5-1 Precautions on disassembly/assembly

5-1-1 Disassembly
1. Get familiar with the constitution and operating principle of the machine prior to disassembly, which is the
precondition for correct disassembly.
2. Not disassemble those without the need. Blind disassembly will not only increase workload of repair but also
damage the original good coordinating relation and precision among parts so as to cause new hidden faults.
3. Use proper disassembly tool and adopt the correct disassembly method. It is prohibited to tap strongly during
disassembly so as to avoid deformation and damage of parts. To enhance repair efficiency, it prefers to use
special disassembly tools.
4. The disassembly must be gradually conducted from the outside to the inside. Generally, the disassembly order
is “overall machine, assembly, components and then parts”.
5. To assemble the machine smoothly after repair, the following shall be noted during disassembly:
1) Check and make marks (such as scribing, arrow and text on some parts). For parts without marks, make signs
on non-operating sides so as to re-install them correctly.
2) Place parts reasonably and store them in categories. Parts of the same assembly or components shall be stored
together. Parts (e.g. gasket) that are easily to be deformed or lost shall be stored separately.

5-1-2 Assembly
1. The assembly site shall be clean.
2. Prepare proper assembly tools and devices.
3. Parts must be cleaned and dusts, soil, metallic debris, carbon deposition, grease stain and other impurities shall
be removed from the surface. Clean and blow it with compression air, cleaning agent, etc.
4. As per the opposite order of disassembly, i.e. assemble as per the order of “from inside to outside and from
main part to auxiliary part” and “parts, components, assembly, and then overall machine”.
5. Note to check part marks and assembly signs during assembly so as to avoid neglected assembly.
6. When assembling fastening parts, fasten it from center to both sides and diagonal crossing direction to fasten it
for several times. Then fasten it in place with torque wrench.
7. Timely replace each sealing gasket during assembly.
8. Conduct the test running for the machine after the overall machine is assembled, adjusted and checked without
errors.

- 34 -
Chapter V Disassembly & Repair

5-2 Disassembly and maintenance of engine

5-2-1 Air filter

Air filter connecting pipe Inner

filter
Assembly: clean the Air filter seat cartridge
inside and replace tubes
with aging or crack. Disassembly/assembly: clean
the inside with compressed
air and then install.

Air filter cover

Element, air cleaner

Assembly
Clean or replace dirty
or damaged filter
Air filter cartridges.
pressboard

- 35 -
Chapter V Disassembly & Repair

5-2-2 Silencer

Silencer
Hexagon nut M8 (4)
Assembly:
Torque: (27 ~ 30) N•m Tap with plastic hammer to
remove carbon deposition and
Flange bolt M8 × 16 (2) then install.
Torque: (22 ~ 26) N•m

Gasket of
exhaust port
Assembly
Replace deformed or
damaged gaskets.

- 36 -
Chapter V Disassembly & Repair

5-2-3 Fan cover - starting control switch

Harness of starting
control switch
Plate,fan cover

Starting control switch

Oil pipe

Assembly: check if the pipe

is aged or cracked before
installation. Fan cover part

Voltage regulating
rectifier

Radiator part

Assembly Flange bolt M6 × 16

Surface shall be clean, smooth, flat
without wrinkling, strain, bruise and
other defects, or it shall be cleaned or
replaced immediately.

- 37 -
Chapter V Disassembly & Repair
b. Check
Engine switch
Check the conductivity of switch terminal at each location of the switch.

1. When the switch is under the Off status, connect the orange terminal to the switch (at the surface of lock nut
of the switch);
2. When the switch is under the On or electric starting (St) status, disconnect the orange terminal to the switch
(at the surface of lock nut of the switch);
3. When the switch is under the electric starting (St) status, connect the red terminal of starting engine to the
white one;
4. When the switch is under the On or electric starting (St) status, connect the black/white terminal of carburetor
to the switch (at the surface of lock nut of the switch);
5. When the switch is under the Off, On or electric starting (St) status, connect the green and blue terminals of
carburetor to the switch (at the surface of lock nut of the switch);

- 38 -
Chapter V Disassembly & Repair
Voltage regulating rectifier
120W
2900rpm~3900rpm,
Module output voltage:DC13.8±0.5V;

It should carry rated load 120W ,voltage should more

than DC13V；
Current limiting protection: when the load current
is greater than 9A, voltage stabilizer into protection
state, but maintain the output 12A current;

180W

2900rpm~3900rpm,
Module output voltage：13.8±0.5V;

It should carry rated load 180W ,voltage should more

than DC13V；
Current limiting protection: when the load current
is greater than 16A, voltage stabilizer into protection
state, but maintain the output 19A current;

260W

2900rpm~3900rpm,
Module output voltage：13.8±0.5V;

It should carry rated load 260W ,voltage should more

than DC13V；
Current limiting protection: when the load current
is greater than 20A, voltage stabilizer into protection
state, but maintain the output 23A current;

- 39 -
Chapter V Disassembly & Repair

5-2-4 Carburetor
Warning
The gasoline is flammable and explosive. The fuel stop valve must be closed before repairing the
carburetor and drain the fuel in the carburetor.

Air filter seat

Assembly
Dirty, damaged or deformed one shall be
cleaned or replaced immediately.

Carburetor sealing gasket

Carburetor

Carburetor
insulation gasket
Fuel tube

Carburetor
sealing gasket

Fuel tube

It shall be regularly replaced

every two years. Air inlet pipe
Assembly: check if the tube
is aged or cracked before
Fuel filter Assembly
installation.
Dirty or damaged one
Assembly shall be cleaned or
Gasoline pump Check if the filter replaced immediately.
cartridge is clean
Assembly: without damage.
Appearance is not
damaged, pump oil flow
capacity is normal and
there is no fuel leakage.

- 40 -
 Chapter V Disassembly & Repair

Disassembly/assembly
Note: clean the carburetor prior to installation
Idle jet
Assembly:
Clean thoroughly with compressed air
Idle mixture adjusting screw before installation and slightly lubricate
Assembly: the O-ring. O-ring
Check the wear at the front
before installation.

Choke-valve shaft
Carburetor body
Assembly:
Blow in compressed air
and remove dirt in the
passage before installation.

Throttle-valve shaft
Needle valve

Assembly:
Check the wear of the end and
Float action of spring before
installation.
Assembly: Float pin
Touch with finger
after installation to
confirm its action.
Float pin Needle-valve seat
Electron magnetic valve
Needle valve
Main jet
Primary nozzle

Assembly:
Blow in compressed
Normal Replace
air and remove dirt in
the passage prior to
installation.
Primary nozzle
Assembly:
Blow in compressed air
and remove dirt in the
Oil drain plug of oil cup passage before
Confirm if there is installation.
fuel leakage after
installation.
Float chamber

- 41 -
Chapter V Disassembly & Repair

c. Check of float height

Place carburetor according to the figure and push in the float
with fingers.
When the float valve touches the float seat and the spring
doesn’t compress, measure the dimensions between float and
the shell (height of the float).

Special tool

Standard height 14±1.5 mm Float height gauge

When the height of float is inconsistent with the specified value, replace the float or float valve.

d. Clean the carburetor

Warning

When
hen using the compression air, to avoid injury, wear
protective spectacles or other protective equipment.

Note
Some chemical solvents are of relatively-strong
relatively corrosivity
and may damage plastic parts such as the O-ring
O and float.
Please
lease carefully read the Solvents Manual. Should you not
confirm, don’t use the solvent to clean the carburetor. The
compression air of high pressure may also damage the
carburetor. Please
lease remove the dirt in the passage or pipe
mouth with compression air of proper pressure.

1) Clean the carburetor with cleanser.

2) Blow in the compression air to remove dirt in idle

idl air jet, idle jet, air jet, main jet, main nozzle, etc. prior to
installation.

- 42 -
Chapter V Disassembly & Repair

5-2-5 Speed-regulating mechanism

Speed-regulating support

Assembly: Choke-valve
Adjust the speed regulator stem
Fuel control assy. during assembly.
Choke-valve
handle

Throttle lever

Speed-regulating
spring
Nut: M6

Accelerator, rope

Split pin
Needle
Assembly: insert the
bearing
split pin into the
speed-regulating arm Throttle control
slot after the combination
speed-regulating arm
is installed.
Return spring of throttle valve
Speed-regulating arm Assembly:
Assembly: Hang the longer end of the
Confirm if the action is spring on the speed-regulating
smooth after installation. support side in installation.

- 43 -
Chapter V Disassembly & Repair
5-2-6 Flywheel and ignition coil
a. Disassembly/assembly

Starting engine part

Flange bolt M8 × 95
Torque: (22 ~ 28) N•m Ignition coil

Assembly:
Prior to installation,
check if the insulation is
cracked or damaged so as
to avoid electric leakage
leakage.

Flange bolt M6 × 30
Air guide sleeve Torque: (8 ~ 12) N•m

Charging coil

Flywheel bolt M12 × 35

Torque: (80 ~ 100) N•m
Prevent the rotation of
flywheel with tool
during the disassembly
Inner hexagon and assembly.
screw
M6×20

Flywheel
Disassembly:
Disassemble
isassemble the ignition coil prior to the
disassembly of flywheel;
flywheel
Do not tap the flywheel with hammer and
disassemble it with a commercially
available flywheel puller.
puller
Blade wheel

Assembly:
Align two cams at the inner side
with the small holes on the
flywheel.
Flywheel puller Avoid excessive force in
Assembly: disassembly and assembly so as to
Clean the conical part of the crankshaft avoid breaking the blade
blade.
and flywheel without engine oil or dirt
before installation.
installation
- 44 -
Chapter V Disassembly & Repair
b.Adjustment of clearance between ignition coils
When re-assembling the ignition coil, adjust the clearance
between ignition coil and flywheel.
1) Slightly screw the mounting bolt of ignition coil.
2) As shown in the figure, insert the thickness gauge into
the clearance of ignition coil and flywheel, or
Insert the paper of the same thickness on the circle of
the flywheel.
3) Press the ignition coil on the flywheel with hand and
4) fasten these two bolts.
Ignition coil
Clearance of ignition coils 0.3 ~ 0.4 mm

Note
0.3 ~ 0.4 mm
a) Adjust two ends of the ignition coil to the same clearance. Flywheel
b) Avoid magnet steel of flywheel when adjusting.

Check
Ignition coil:
<Resistance value at the primary side>
Connect the tester terminal with the conductor terminal and
coil iron core to measure the resistance value at the primary side.

Resistance value at the

1.0-1.4 Ω
primary side

<Resistance value at the secondary side>

Connect the tester terminal with the high-voltage wire with the
spark plug cap removed and the coil iron core to measure the
resistance value at the secondary side.

Resistance value at the

6.2-7.6 KΩ
secondary side

Note
Not removing the spark plug cap during measurement will cause false readings.

- 45 -
Chapter V Disassembly & Repair
c. Spark plug cap
Connect the ohm gauge to the two ends of the spark plug
cap to measure the resistance of spark plug cap.

Resistance value 9-11 KΩ

Replace the spark plug cap if the resistance value doesn’t

meet specifications.

Charging coil
120W
Use multimeter to test the voltage between the two yellow
lines of charging coil when the engine is of no load:
Average no-load voltage (32±2) V and peak voltage (84±4) V.
Equipped with the voltage regulator with 120 W load, and
the Voltage not less than DC13V Yellow wire

180W
Use multimeter to test the voltage between the two yellow
lines of charging coil when the engine is of no load:
Average no-load voltage (32±2) V and peak voltage (84±4) V.
Equipped with the voltage regulator with 180 W load, and
the Voltage not less than DC13V

260W
Use multimeter to test the voltage between the two yellow
lines of charging coil when the engine is of no load:
Average no-load voltage (33±2) V and peak voltage (86±4) V.
Equipped with the voltage regulator with 260 W load, and
the Voltage not less than DC12.5V

- 46 -
 Chapter V Disassembly & Repair

5-2-7 Cylinder head and valve

Disassembly/assembly

Flange bolt M10 × 65

Flange bolt M6 × 25 Torque: (50 ~ 55) N•m
Torque: (8 ~ 12) N•m Assembly/disassembly:
Loosening and fastening of bolt must be done by
Oil stopper
way of crossing, especially when fastening the bolt.
Each bolt must be gradually tightened evenly to the
specified torque.

Air guide sleeve

Cylinder-head
Cylinder-head
sealing gasket
cover

Cylinder-head
cover sealing
gasket

Spark plug

Torque: (25 ~ 30) N•m

Assembly: clean and
adjust the spark plug Cylinder-head part
prior to installation. Assembly: Locating pin

Remove the carbon deposition in

combustion chamber and check the
touching status of valve seat prior to
installation.
Measure the pressure of cylinder
after assembly.

- 47 -
Chapter V Disassembly & Repair

Valve rocker arm

Assembly:
Nut M6
Check if the contact surface of
rocker arm, central hole or valve
Torque: (12 ~ 16) N•m lifter is worn prior to installation.
Tappet combination

Assembly:
Confirm the wear of two ends
and upright of lifter body, and
then pass through the guide hole
and place into the crankcase
Plate,push rod lifter to install it in place.
guide

Valve lock clamp

Valve lifter
Assembly:
Don’t drop the tappet
during installation and
Oil drip pan then install the camshaft
immediately.

Valve spring seat

Inner valve spring

Valve-adjusting cap Inner valve spring

seat ring
Assembly:
If the valve-adjusting cap
is missed to be installed, Exhaust valve
it may cause valve into
the cylinder when the Assembly:
engine is under Confirm if the conical
Inlet valve
operation. part is defected or there is
excessive carbon Assembly:
deposition prior to Don’t confuse these valves.
installation. Be careful during
installation and don’t
damage the valve stem.

- 48 -
Chapter V Disassembly & Repair
Free length of the valve spring
Measure the free length of valve spring.

Standard Maintenance Limit

39.5~40.5 mm 39 mm

Replace the spring if the maintenance limit is exceeded.

Width of valve seat

Remove the carbon deposition in combustor and check if
the valve seat has corrosion or damage.
Measure the width of valve seat.

Standard Maintenance Limit

0.7~0.8 mm 2.0 mm

If the width of valve seat is less than the standard value or

exceeds the maintenance limit, trim the valve seat once.

Cylinder head Straightedge

STRAIGHT EDGE
1. Remove the carbon deposition in combustor and residues
of gasket attached onto the cylinder head.
2. Check if there is any crack at the spark plug hole, valve
seat surface and valve pipe.
3. Check if there is deformation of cylinder head with straightedge
or thickness gauge as shown in the figure.
FEELER GAUGE
Thickness gauge
Maintenance Limit 0.10 mm

Outer diameter of valve stem

Check each conical side of the valve to see if there is any uneven,
curved or abnormal wear of valve stem.
Replace the valve if necessary. Measure and record the outer
diameter of each valve stem.

Standard Maintenance Limit

- 49 -
Chapter V Disassembly & Repair
Inlet
6.565~6.58 mm 6.438 mm
valve
Exhaust
6.545~6.56 mm 6.435 mm
valve
Replace the valve if the outer diameter of valve stem is less than the maintenance limit.

Inner diameter of valve guide

Remove the carbon deposition in the exhaust valve pipe with
reamer prior to measurement.
Measure and record the inner diameter of each valve guide.

Standard Maintenance Limit

6.6 ~6.615 mm 6.672 mm

Clearance between valve guide and valve stem

Deduct the outer diameter of valve from the corresponding inner
diameter of valve guide.
Obtain the clearance between the valve guide and valve stem.

Standard Maintenance Limit

Inlet valve 0.02 ~ 0.05 mm 0.15 mm
Exhaust valve 0.04 ~ 0.07 mm 0.17 mm

If the clearance value between the valve stem and guide exceeds the maintenance limit, judge if replacing a new
guide of standard dimension will make the clearance achieve within the maintenance limit; if yes, replace the
valve guide (or cylinder head) as required and ream the valve guide to make it a better coordination. If the
clearance between the valve stem and new valve guide still exceeds the maintenance limit, replace the valve too.
Trim the valve seat again when replacing the valve guide.

Trim the valve seat

1. Thoroughly remove the carbon deposition in the combustor and

on the valve seat.

2. Coat a thin layer of blue lead power on the surface of the valve

or ink of marking pen which is easily to be erased.

3. Insert into the valve and press it for several times to make it tightly close to the valve seat. Assure not to rotate
the valve on the valve seat. Coating on the valve seat will show the de-concentric feature of valve or valve

- 50 -
Chapter V Disassembly & Repair
seat.

4. Grind the valve seat with a 45° grinder to make the valve seat smooth and concentric; operate as per the
manual of valve seat grinder provided by the manufacturer.

Rotate the grinder clockwise and the anticlockwise rotation is not allowed.
Lift the valve seat grinder from the valve seat and continue grinding.

High contact surface

5. Shorten and adjust the valve seat a 30°-32° and 60° grinders,
Make the valve seat connect with the central part of the valve surface.
Grind the top edge of the valve seat with a 30°-32° grinder.
Grind the bottom edge of the valve seat with a 60° grinder.
Low contact surface
Assure the contact width of valve seat after completion is within
the specified scope.
Width of valve seat

Standard Maintenance Limit

0.7~0.8 mm 2.0 mm

1. Slightly grind with the 45° grinder to remove any burr at the edge
of valve seat.
2. After trim the valve seat again, check that after the valve is put in,
if it contacts evenly.
3. Coat a thin layer of blue crocus on the surface of the valve or ink
of marking pen which is easily to be erased.
4. Insert into the valve and press it for several times to make it tightly
close to the valve seat. Assure not to rotate the valve on the valve seat.
If colorant is evenly coated on the conical side of the valve seat as
shown in the figure, it indicates that the contact between valve and valve
seat is good.

Valve grinder
Note:
To avoid severe engine damages, thoroughly remove the abradant
on the cylinder head prior to assembly.

5. Check the valve clearance after assembly.

- 51 -
Chapter V Disassembly & Repair
5-2-8 Secondary oil filter, breather slot and air guide sleeve
Disassembly/assembly
Breather tube
Assembly: check if the pipe
Breather-slot is aged or cracked before
cover plate installation.
Spring valve
Assembly: adjust or
replace deformed or Filter screen
non-completely-sealed
Assembly: edge of the
valves.
Secondary oil filters filter screen is not
exposed and the dirty
Torque: (10 ~ 13) N.m ones are required to be
Confirm if there is engine oil cleaned timely.
leakage after installation.
Regularly replace every 200 h.

Breather-slot
Fine-filter sealing gasket
mounting bolt
Torque: (40 ~ 45) N•m

Air guide sleeve

Air guide sleeve

Engine oil protector Oil seal 43 × 55 × 7 mm

Oil drain bolt Assembly: don’t curl the

edge of oil seal when
Confirm if there is passing through the
engine oil leakage crankshaft.
after installation.

- 52 -
Chapter V Disassembly & Repair
b. Check
Engine-oil protective system

Engine oil Oil level

protector alarm

The engine-oil protective system is designed for preventing damage from insufficient engine oil inside the
crankcase. When the oil level decreases under the safety line, the engine-oil protective system will automatically
shut down the engine (the switch of engine is still at the location of “On”); if the engine stops automatically and
cannot start, firstly check the oil level and other faults then.
1) When the engine is under operation, disconnect the yellow lead wire of engine-oil protector and ground
through the engine to confirm that the engine is shut down.
2) After shutting down the engine, it is normal that under the case that engine oil quantity meets specifications and
don’t disconnect the yellow lead wire of the oil level alarm, the yellow lead wire is conductive to the earth wire.
3) When the oil-level sensor grounds and the rotating speed of engine is less than 800±50 rpm, the engine-oil
protector will not act; when the rotating speed of engine is greater than 800±50 rpm, the engine oil protector
delays action for (1.8±0.2)S and the igniter flames out; when the engine operates normally and the oil-level sensor
grounds, the engine-oil protector delays action for 1 S.

- 53 -
Chapter V Disassembly & Repair
5-2-9 Crankcase, crankshaft and piston
Disassembly/assembly
Speed-regulating gear

Assembly:
Camshaft
. Check if the speed-regulating gear is
worn or damaged prior to installation. Align the gear of camshaft
. Confirm if the speed-regulating gear with the timing gear on the
rotates flexibly without obvious axial crankshaft during installation.
Bolt M8 × 50 drifting after installation.

Torque: (25 ~ 30) N•m Oil-level

gauge Comparison mark

Speed-regulating arm

Assembly:
Confirm if the
action is smooth
Crankcase-cover after installation.
sealing gasket

Crankcase cover

Engine-oil filter screen

Dirty or damaged one Connecting-rod
shall be cleaned or bolt
replaced immediately. Torque:
12 N.m±1 N.m

Crankshaft part
Assembly:
Don’t damage the oil
seal during installation.
Piston
Assembly: Connecting rod Crankcase body
Point the “▽” mark at the top of the Assembly: coat adequate lubricating oil
piston to the opposite direction of on the bigger end hole in a full circle.
rotation of crankshaft (seen from the Connecting-rod boss has the same
output end of engine, the piston direction with that of the piston arrow
arrow of the right cylinder is while the other is opposite.
downward and the piston arrow of
the left cylinder is upward).
- 54 -
 Chapter V Disassembly & Repair

Disassembly/assembly
Piston and connecting rod
Assembly:
. Put upward the manufacturer’s mark
during assembly.
Ring 2 . Do not misplace the gas rings 1 and 2.
. Check if the piston ring can rotate
Opening of ring 2 Piston mark flexibly after installation.
Ring 1
. Avoid the direction of piston pin for each
opening of piston ring by staggering for
150° ~ 210°.

Ring 1
Ring 2
Mark
Oil ring
Oil rings
Opening of ring 1
Connecting rod
Assembly: point the “▽” mark of the
piston to the same direction of that of the
Note: connecting-rod boss during assembly while
Openings of rings 1 and 2 shall be staggered the other is in the opposite direction.
for 150° ~ 210°.

Note:
Opening of blade ring of oil ring shall be
staggered for 150°~ 210°.

Bigger end hole

Coat adequate lubricating
oil on the bigger end hole
of the connecting rod in a
Steel wire retaining ring full circle.
Assembly:
Put one end to the slot of the piston,
and clamp the other end with the Piston pin
long nose pliers; rotate and install it
into the slot. Don’t make the
opening of the clamp ring face the Note: point the “▽” at the top of the piston
gap of the piston pin. to the opposite direction of rotation of the
crankshaft (seen from the engine output
end, the piston arrow of the right cylinder
is downward while the piston arrow of the
left cylinder is upward).

- 55 -
Chapter V Disassembly & Repair
Check

Installation check of oil pump Outer rotor

1、 Rotational flexibility of rotator: coat lubricating oil onto

rotator and axis prior to assembly; manually rotate the rotational Oil pump
driven wheel
axis after assembly to assure no binding in rotation process.
2、 Pumping of oil pump: after assembly, add certain engine oil at
the filter screen of the oil inlet for the oil pump, manually rotate
the gear of oil pump to assure the oil pump can pump oil, otherwise,
re-assemble or replace the oil pump.
Inner rotor Sealing ring

Outer diameter of piston pin

Standard Maintenance Limit

16.992-16.998 mm 16.9 mm

Inner diameter of cylinder

Measure the three points on X and Y axes and record the inner
diameter of the cylinder (X axis is perpendicular to crankshaft
while Y axis is parallel to crankshaft).
Take the maximum reading as the wear and conical degree of
the cylinder.

Standard Maintenance Limit

80.0-80.01 mm 80.15 mm

Detection of piston and piston ring

Check the contact between piston and cylinder, defects of ring groove, erosion at the top, crack, etc. It shall be
replaced for severe damages (e.g. crack).
Remove carbon deposition
Carbon deposition accumulates at the edge of the top of piston and upper opening of cylinder. Remove carbon
deposition prior to detection. Wet the carbon deposition with kerosene, and then remove it with blunt scraper or
metallic brush.

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Chapter V Disassembly & Repair
Outer diameter of piston skirt

Measure and record the outer diameter of piston skirt at the

place 10 mm away from the maximum lower edge of the
piston skirt; the measuring direction is perpendicular to the
piston pin hole.

Standard Maintenance Limit

79.965-79.975 mm 79.755 mm

Clearance between piston and cylinder

The difference between the maximum diameter of cylinder and
the diameter of the piston skirt is the clearance between piston and cylinder.

Standard Maintenance Limit

0.025-0.045 mm 0.255 mm

Clearance to the side of piston ring

Standard Maintenance Limit

Gas ring 1
0.02-0.06 mm 0.11 mm
Gas ring 2
Oil ring 0.03-0.08 mm 0.15 mm

Width of piston ring

Standard Maintenance Limit

Gas ring 1 2.9 mm 2.77 mm
Gas ring 2 3.3 mm 3.17 mm
Oil ring 2.6 mm 2.07 mm

Clearance to the end of piston ring

Standard Maintenance Limit

Gas ring 1 0.2-0.4 mm 0.7 mm
Gas ring 2 0.3-0.5 mm 0.8 mm
Oil ring 0.2-0.7 mm 1.0 mm

Before measuring the clearance to the end of piston ring, locate the piston ring with the top of the piston to make
it not erect in the inner hole of the cylinder.

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Chapter V Disassembly & Repair

Inner diameter of piston pin hole

Standard Maintenance Limit

17.002-17.008 mm 17.12 mm

Clearance between piston pin hole and piston pin

Standard Maintenance Limit

0.004-0.016 mm 0.029 mm

Detection of connecting rod

The connecting rod shall be scrapped to change a new one when it is bent or warped, or there is abnormal wear to
the larger end and small end hole or there is crack of one side.

Inner diameter of the small end of connecting rod

Change the connecting rod if the inner diameter is less than the
standard or more than the maintenance limit.

Standard Maintenance Limit

17.006-17.017 mm 17.05 mm

Inner diameter of the big end of connecting rod

Change the connecting rod if the inner diameter is less than the

standard or more than the maintenance limit.

Standard Maintenance Limit

40.015-40.025 mm 40.065 mm

Detection of crankshaft
Conduct 100% inspection to the cleaning condition inside the oil passage prior to the installation of crankshaft and
clean the oil passage with blow gun to ensure there are no impurities in the oil passage.

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Chapter V Disassembly & Repair
Outer diameter of the crankshaft journal

Standard Maintenance Limit

39.966-39.991 mm 39.906

Side clearance of the big end of connecting rod

Standard Maintenance Limit

0.203-0.403 mm 1.0 mm

Oil-film clearance of big end of connecting rod (radial direction)

1) Clean the surface of crankshaft journal and the inside oil.
2) Set plastigauge on crank journal then assemble the connecting
12 N.m±1 N.m
rod, and fasten the bolt as per the specified torque.

Fastening torque: 12 N.m±1 N.m

Note

Don’t rotate the crankshaft when fastening the connecting-rod bolt.

Calibrate with torque wrench in N+1 way and conduct 100%
inspection to the crankshaft to see if it rotates flexibly.

3) Disassemble the connecting rod and measure the thickness of

Plastigauge
plastigauge.

Standard Maintenance Limit

0.024-0.059 mm 0.115 mm

4) When the clearance exceeds the maintenance limit, replace

the connecting rod and check the clearance again. If the clearance
still exceeds the maintenance limit after using new connecting
rod, grind the crankshaft journal and use the connecting rod less
than the standard value.

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Chapter V Disassembly & Repair
Detection of camshaft

The camshaft is the main engine drive element of valve mechanism of gasoline engine, controlling inlet or
exhaust valve to open or close in a regular manner.
For appearance, check whether the cam surface and the height is damaged, whether the camshaft and bearing is
loose and worn. If yes, change the whole unit.

Height of camshaft
Maintenance
Standard
Limit
Inlet 29.95-30.05 mm 29.75 mm
Exhaust 29.95-30.05 mm 29.75 mm

Outer diameter of camshaft

Standard Maintenance Limit

15.966-15.984 mm 15.916 mm

Note the position of depression mechanism and check to

ensure its flexibly.

Inner diameter of camshaft bearing hole

Standard Maintenance Limit

16.0-16.018 mm 16.068 mm

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LONCIN MOTOR CO., Ltd.

Add: No.99 Hualong Road, Jiulongpo District, Chongqing, China

Tel: 86 23 8906 7577/7599

Fax: 86 23 8906 7533

Web site: www.loncinengine.com

E-Mail: marketing@loncinengine.com

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