Cobra Y173V User manual

MODEL: Y173V
COBRA ENGINE
SERVICE MANUAL
Cobra Garden Machinery
Henton and Chattell Ltd., London Road, Nottingham NG2 3HW UK
www.cobragarden.co.uk

CONTENT
CONTENT
1. INTRODUCTION...............................................................................................................1
1-1 Parts Description......................................................................................................... 1
1-2 Specifications ............................................................................................................. 2
1-3 Service Limit .............................................................................................................. 2
2. DIMENSION AND TORQUE ...........................................................................................4
2-1 Dimension................................................................................................................... 4
2-2 The Position Of Installing Hole.................................................................................. 5
2-3 PTO Installing Drawing.............................................................................................. 5
2-4 Torque Value.............................................................................................................. 6
2-5 Standard Torque Value............................................................................................... 7
3. MAINTENANCE ...............................................................................................................8
3-1 Maintenance Schedule................................................................................................ 8
3-2 Engine Oil................................................................................................................... 8
3-3 Air Cleaner................................................................................................................ 10
3-4 Wash The Strainer .................................................................................................... 11
3-5 Spark Plug ................................................................................................................ 11
3-6 Valve Clearance Adjustment.................................................................................... 12
3-7 Governor................................................................................................................... 14
4. DISASSEMBLING AND SERVICING...........................................................................15
4-1 Troubleshooting........................................................................................................ 15
4-1-1 Starting Difficult............................................................................................ 15
4-1-2 Power Lack.................................................................................................... 17
4-1-3 Speed Unstable.............................................................................................. 18
4-1-4 Unable Igniting.............................................................................................. 18
4-1-5 Gasoline Engine Is Overheat......................................................................... 19
4-1-6 Abnormal Sound ........................................................................................... 19
4-2 Preparation Of Servicing .......................................................................................... 20
4-2-1 Safety Precautions......................................................................................... 20

CONTENT
4-2-2 Special Tools................................................................................................. 21
4-3 Dismounting Chart.................................................................................................... 22
4-4 Gasoline Engine........................................................................................................ 23
4-4-1Recoil starter / fan cover ................................................................................ 23
4-4-2 Muffler .......................................................................................................... 26
4-4-3 Fuel Tank....................................................................................................... 27
4-4-4 Air Cleaner.................................................................................................... 28
4-4-5 Governor........................................................................................................ 30
4-4-6 Carburetor...................................................................................................... 32
4-4-7 Flywheel........................................................................................................ 37
4-4-8 Cylinder Head / Valve................................................................................... 41
4-4-9 Crankshaft / Piston ........................................................................................ 49
4-5 Electric Diagrams ..................................................................................................... 58
TRANSFORMATION POINTS............................................................................................. 59

1. INTRODUCTION
1
1. INTRODUCTION
1-1 Parts Description
START HANDLE
OIL DIPSTICK SPARK PLUG
MUFFLE
AIR CLEANER FUELTANK COVER

2
1. INTRODUCTION
1-2 Specifications
MODEL
ITEM
Y173V
L×W×H(not including crankshaft
output terminal)
415×345×280(mm)
Dry Weight
13.45Kg
Engine Type
Single Cylinder Horizontal,4-Stroke, OHV
Displacement
173cc
Bore × Stroke
70mm×45mm
Theoretical Maximum Power
3.6kW/3,600r/min
Recommended Using Power
3.0Kw /2800r/min
Maximum Torque
10N·m/2,800r/min
Fuel Consumption
395g/kW·h
Cooling System
Forced Air
Ignition System
Capacitance Discharge Type
PTO Shaft Rotation
Vertical Shaft Output
1-3 Service Limit UNIT：mm
PARTS
ITEM
STANDARD
SERVICE
LIMIT
Engine
Maximum Speed (No Load)
2850±100rpm
--
Idle Speed
2100±100rpm
--
Cylinder Compression
1.40Mpa/1200rpm
--
Cylinder Head
Sleeve I.D
70
70.165
Cylinder Head
Warpage
--
0.10
Piston
Skirt O.D.
69.980
69.865
Piston–to-Cylinder Clearance
0.020-0.050
0.10
Piston Pin Bore I.D.
18.002-18.010
18.040
Piston Pin O.D
17.994-17.998
17.954
Piston Pin-to-Piston Pin Bore Clearance
0.004-0.016
0.08
Piston Rings
Ring Side Clearance：second
0.030-0.065
0.15
Ring Enc Gap: second
0.2-0.4
1.0
Ring Width：second
1.497-1.499
1.397

1. INTRODUCTION
3
Connecting Rod
Small End I.D
18.004-18.012
18.052
Big End I.D
Big End Clearance
30.015-30.025
0.017-0.032
30.050
0.1
Small End Clearance
0.006-0.018
0.08
Crankshaft
Crankshaft Pin O.D
29.993-29.998
29.94
Valve
Valve Clearance IN
EX
Stem O.D IN
EX
Guide I.D IN/EX
Stem Clearance IN
EX
Seat Width
Spring Free Length
0.10±0.02
0.15±0.02
5.465-5.480
5.465-5.480
5.500-5.512
0.020-0.044
0.050-0.077
0.8
64.0
--
--
5.315
5.315
5.562
0.10
0.12
2.0
63
Camshaft
Cam Height IN
EX
Journal O.D
27.70
27.75
13.965-13.990
27.45
27.50
13.915
Crankcase Cover
Camshaft Bracket I.D
14.0-14.018
14.048
Carburetor
Main Jet
#68(DL)or#70（KAMA）
--
Float Height
13.7
--
Pilot Screw Opening
2-5/8turns
--
Spark Plug
Gap
0.7-0.8
--
Spark Plug Cap
Resistance
4.5-5.5kΩ
--
Ignition Coil
Resistance Primary coil
1.0-1.3Ω
--
Secondary coil
10.5-11kΩ
--
Air Gap （at flywheel）
0.30-0.40
--

2. DIMENSION AND TORQUE
4
2. DIMENSION ANDTORQUE
2-1 Dimension

5
2. DIMENSION AND TORQUE
2-2 The Position Of Installing Hole
2-3 PTO Installing Drawing
Q161 Shaft

6
2. DIMENSION AND TORQUE
2-4 Torque Value
ITEMS
FASTENERS
TORQUE VALUE (N·m)
Connection-Rod Bolt
M7×32
15±0.5
Governor Gear Bolt
M6×12
11±1
Crankcase Cover Bolt
M8×50
26±2
Spark Plug
M14-1.25
18±2
Cylinder Head Bolt
M8×50
26±2
Rotation Shaft Locked Nut
M6 × 0.5
11±1
Cylinder Head Cover Bolt
M6×14
10±2
Ventilation Chamber Cover Bolt
M6×12
7±1
Side Shield Bolt
M6×10
10±2
End Shield Bolt
M6×10
10±2
Brake Bolt
M6×35
11±1
Flywheel Nut(Cast Iron)
M14×1.5
80±6
Ignition Wire Bolt
M6×25
11±1
Fuel Tank Support Bolt
M6×12
10±2
Fuel Tank Bolt
M6×22
8±1
Recoil Starter Reel Nut
M6
10±2
Throttle Control Sub Assemble Bolt
M6×10
10±2
Air Cleaner Nut
M6×1.0
10±2
Muffler Cover Nut
M6×1.0
10±2
Engine Cover Nut
M6×1.0
10±1
Drain Plug
M10 × 1.25
18±2
For unspecified bolt, screw and nut, refer to the standard torque value.

7
2. DIMENSION AND TORQUE
2-5 Standard Torque Value
FASTENERS
SPECIFICATION
TORQUE VALUE(N·m)
Bolt, Nut
5mm Bolt, Nut
4.5-6
6mm Bolt, Nut
8-12
8mm Bolt, Nut
18-25
10mm Bolt, Nut
29-34
12mm Bolt, Nut
49-59
4mm Screw
1.5-2.6
5mm Screw
3.5-5
6mm Screw
7-11
5mm Flange Bolt
3.6-6.9
6mm Screw
7-11
5mm Flange Bolt
3.6-6.9
6mm Flange Bolt
10-14
8mm Flange Bolt
20-26
10mm Flange Bolt
35-45

3. MAINTENANCE
10
3. MAINTENANCE
3-1 Maintenance Schedule
FREQUENCY
ITEM
EACH
TIME
FIRST MONTH
OR 20 HRS
EACH SEASON
OR 50 HRS
EVERY 6
MONTH OR 100
HRS
EACH YEAR
OR 300 HRS
Engine Oil
Oil Level
Check
√
Replace
√
√
Air Cleaner
Check
√
Clean Replace
√
Oil Alert
System
Check
√
Spark Plug
Clean,Adjust
√
Replace
√
Oil Strainer
Clean
√
Valve
Clearance
Check-Adjust
√*
Cylinder
Head
Clean
√*
Fuel Tank
Replace
Every three years
*These items should be serviced by company authorized dealer, unless you have the
proper tools and mechanically proficient.
3-2 Engine Oil
●Engine oil is a key factor in deciding the engine’s
performance. Do not apply engine oil with additives or
2-stroke gasoline engine oil, because they haven’t enough
lubrication, and may shorten the engines service life.
●Check the engine with it stopped on a level ground.
●Engine oil capacity: Y173V 0.6L
Engine oil recommended: SAE 10W-30

3. MAINTENANCE
11
When the temperature in your area is in the frame of the above chart, you can use other
viscosity of engine oil.
CHECK METHOD
1. Remove the dipstick and clean it.
2. Reinsert the dipstick into the oil filling hole without screwing it, and check oil level.
3. If the oil level is too low, add the recommended engine oil up to the oil upper limit.
4. Reinstall the dipstick.
OIL CHANGE
Used engine oil contains substances that have been identified as carcinogenic. If
repeatedly left in contact with the skin for prolonged periods, it may cause skin cancer.
Wash your hands thoroughly with soap and water as soon as possible after contact with
used engine oil.
Please dispose of used oil in manner that will pollute the environment. We suggest you
take it in a sealed container to your local service station or recycling center for
reclamation. Do not throw it in the trash or pour it on the ground.
a) Screw the oil dipstick off.
b) Tilt the engine to drain the oil from the hole.
SEALING RING
(Don’t Refuse)
OIL UPPER LIMIT
OIL LOWER LIMIT
OIL DIPSTICK
OIL HOLE

3. MAINTENANCE
12
3-3 Air Cleaner
BREATHE TUBE
GASKET
CASE
NUT M6
PAPER FILTER ELEMENT
FOAM FILTER ELEMENT
COVER
Wash the engine each 50 hrs (or 3 months). (Wash more frequently in dust area)
Remove the air cleaner cover and take the element out.
Change the damaged element.
Clean the element before reusing.
Clean the element：
Foam Element
Wash the element with detergent and dry it.
Immerse the element into the oil and squeeze the excessive oil. The element should
be wet, but not drop the oil.
Paper Element
Blow the compressed air from the inner side or lightly tap to move the dust. If dirty
badly, replace in time.
Be careful to prevent dirt from entering the air duct that leads to the carburetor.
Place the foam element over the paper element, and cover the case cover on.

3. MAINTENANCE
13
FUELTANK
CLIP
OILTUBE
STRAINER
SIDE ELECTRODE
3-4 Wash The Strainer
Don’t smoke or use fire near the flammable solvent.
a) Fill the fuel into the container
b) Remove the fuel tube, screw the
strainer bolt off.
c) Check the strainer for damage and
clean the strainer.
d) After Cleaning, install the strainer on
the fuel tank and connect the fuel tube.
e) Check for leaking.
3-5 Spark Plug
a) Remove the spark plug cap. Clear away dirt around
the spark plug base
b) Dismantle the spark plug with a spark plug wrench.
SPARK PLUG SOCKET WRENCH
SPARK PLUG CAP
c) Visually check the spark plug. Clean with a Steel brush.
If the insulator is damaged, replace the spark plug
instead.
d) Measure the spark plug clearance with a
feeler. The clearance should be 0.7~0.8mm.
If adjustment is necessary, bend the side
electrode carefully.
0.70~0.80mm

3. MAINTENANCE
14
e) To avoid cross-threading, first, screw in spark plug by hand,
then tighten with a spark plug wrench to compress the gasket.
f) If a new spark plug is used, more twist 1/2 turns after
compressing the gasket.
g) If reinstalling the used spark plug, just more twist 1/8-1/4 turns.
Spark plug torque value：18±2N·m
Spark Plug Type：F7TC
The spark plug must be tightened securely, or it may become very hot to damage the
engine. Only use recommended spark plug or the equivalent. Incorrect heat range of
the spark plug may damage the engine.
3-6 Valve Clearance Adjustment
Measure the valve clearance in the cold of the engine state.
SPARK PLUG
SPARK PLUG CAP
a) Remove the bolt（M6×14）, cylinder head cover, gasket, spark plug cap and spark plug.
GASKET
CYLINDER HEAD COVER
BOLT M6×14

3. MAINTENANCE
15
FEELER
After the cylinder head cover is removed, engine oilmay flow. Be
sure to wipe up any flowed oil.
b) Pull the starting rope lightly and set the piston at top dead
center of the compression stroke (Insert a feeler gauge
between the rocker arm and valve to measure the valve
clearance).
c) Measure the valve clearance with feeler.
d) Valve clearance adjustment method:
Loose the locking nut, turn the adjusting nut to get the correct
valve clearance. Screw down the locking nut. Torque value：
10N.m
e) Recheck the valve clearance
f) Set the new gasket with the projection of the cylinder head
g) Install the cylinder head cover and tighten the four bolts to the specified torque.
Torque value ：6N.m
Standard Valve Clearance
Intake Valve
0.10±0.02mm
Exhaust Valve
0.15±0.02mm
Adjusting Nut
Value Clearance
Screw Down
Decreasing
Screw Off
Increasing

3. MAINTENANCE
16
THROTTLE VALVE
GOVERNOR SUPPORT
GOVERNORARM
NUT M6
Clearance too big: Intake and exhaust valve opening delay will shorten the intake and
exhaust time, lower the opening height of the valve and change normal distributing phase to
result in power lowering from the intake lack and exhaust uncompleted. Furthermore, also
make vale train parts knock increasing and wearing quickly.
Clearance too small: After running, engine parts will be heated to expand and push the valve
open, which will make the engine not closing tight and result in leaking, power lowering,
serious carbon deposit or burn on the valve surface, even valve impacting the piston.
3-7 Governor
Governor
adjustment
a) Remove the air cleaner.
b) Loosen the nut (M6). Be sure that
the carburetor throttle valve is
fully open.
c) Rotate the governor support shaft
fully to the right (governor fully
closed position), and tighten the
nut.
TORQUE VALUE: 10-12N.m
d) Check to see that the governor support and throttle valve move freely.
e) Check the maximum engine speed
Maximum SpeedAdjustment
a) Start the engine and allow it to warm up to normal operating temperature.
b) If the maximum speed not conforming to specified value, adjust the adjusting bolt
M4×30.
Engine maximum speed：2850±100rpm
Speed too big
Turn the bolt counterclockwise.
Speed too small
Turn the bolt clockwise

17
4. DISASSEMBLING AND SERVICING
4. DISASSEMBLINGANDSERVICING
4-1 Troubleshooting
4-1-1 Starting Difficult
TROUBLE
CAUSE
REMEDY
Normal cylinder compression
Normal spark plug spark
Something wrong with the fuel system.
Fuel supply is not smooth or no
fuel supply.
There is no enough fuel in fuel tank and
fuel cock is closed.
Fill fuel, open fuel cock.
Air vent in the fuel filler cap is clogged
Dredge air vent.
Improper or clogged main oil flow hole.
Readjust or clean, blow to
get through.
Needle valve is not closed properly or
start hole is clogged.
Dismantle needle valve and
repair, clean, blow to get
through.
Float is damaged or sticking.
Repair float
Fuel supply is normal.
Fuel is too filthy or deteriorated
Replace
There is water in fuel.
Replace
Too much fuel in engine
Drain extra fuel, dry up spark
plug electrodes.
Wrong fuel brand
Select proper fuel brand
corresponding with the
requirements.
Normal fuel supply system.
Normal high
–tension line
spark.
Spark plug is in
bad conditions
Too much carbon deposit and dirt around
electrodes.
Clear away.
Electrodes are burn damaged seriously
or insulators damaged.
Replace spark plug.
Improper electrodes gap.
Adjust to proper value.
High-tension line
no spark
Normal spark
plug
High –tension line is damaged.
Replace
Ignition coil is damaged.
Replace
Magneto loses magnetism.
Replace
Abnormal gap between the ignition coil
and flywheel.
Adjust gap

18
4. DISASSEMBLING AND SERVICING
TROUBLE
CAUSE
REMEDY
Abnormal cylinder compression.
Normal fuel supply system.
Normal spark plug.
Piston ring is worn to or even over its
wear limit
Replace
Piston ring is broken.
Replace
Piston ring is sticking.
Clear up carbon fouling.
Spark plug is not installed tighten or
without a gasket.
Tighten with a gasket in.
Air leakage between cylinder block
and cylinder head.
Check cylinder gasket, and the flatness of the
surface by which cylinder block contacting with
cylinder head
Tighten cylinder head bolts in stipulated order to
stipulated torque.
Air leakage in the valves
Check valve. Clearance and tightness, repair if
necessary.
If still can’t starting, have the engine to our authorized dealer for repairing.
●Spark plug testing
Make sure there is no spilled fuel outside the engine and that the spark plug isn’t
dipped with fuel.
When testing the spark plug, never hold the high- tension line of the spark plug
with wet hand.
To prevent fire, keep sparks far away from the spark plug mounting hole.
SPARK PLUG,SPARK PLUG CAP
RECOL STARER GRIP