Zenoah G320PUM User manual

OWNER'S MANUAL
115767226 (508)
Model: G320PUM for radio control Boat
Model code: 967289101
WARNING
•This engine is designed for radio controlled boat use.
•When replacing parts, use only parts which have been certified by
Zenoah.
•Zenoah assumes that no responsibility for this engine that is modified
or used for any other applications.
•Purchaser has all responsibilities against any laws and regulations
existing in the country, Zenoah is exempt from such laws and
regulations.
•Read and completely understand this OWNER'S MANUAL before
operating this engine.

2

3
Safety Precautions ....................................................4
Engine Assembling....................................................5
Engine Mounting........................................................6
Screw Propeller and Exhaust System .......................7
Fueling System..........................................................8
Starting ......................................................................9
How to Stop The Engine............................................9
Carburetor Adjustment ............................................10
Engine Break-In.......................................................12
Operation.................................................................12
Maintenance............................................................13
Special Tools...........................................................18
Service Guide..........................................................19
Trouble Shooting .....................................................22
Parts List..................................................................24
Warranty..................................................................27
Contents

4
Safety Precautions
•This manual describes the engine. For its mounting and control, see the
instruction manual provided by model boat manufacturer.
•This engine is designed for model boat use. If it is used for any other purpose,
we cannot be responsible for its reliability, safety and any laws/regulations in
the country.
•Use genuine parts for replacement.
•Check the rotor and screw-propeller every time. If it is damaged, replace it
with a new one.
•If the screw-propeller hit something while the engine is in operation,
immediately stop the engine and check it.
•Start the engine on a flat surface without pebble stones.
•Never modify the rotor.
•Check the rotor. If it is damaged, replace it with a new one.
•When mixing the fuel, or operating the engine, carry it out in a well-ventilated
place.
•The fuel is toxic. Do not let it get into your eyes or mouth. Store it in a cool
place, out of the reach of infants and children.
•To prevent electrification, never touch the high-tension wire of the spark plug
during operation.
•The engine metal parts can burn your skin. Never touch the engine and
muffler during operation or right after stopping the engine.
•Please wear clothing that facilitates your safety. Remove all scarves, overly
long sleeves, neckties and like. Failure to do so could result in injury.

5
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34
6
57
1
The carburetor and air-funnel are not assembled at factory.
Make sure that the assembling for such parts are done according to the Fig.1.
Make sure that gasket and carburetor are mounted as described in fig.1.
The engine does not start if carburetor is mounted upside down position.
CAUTION
Engine Assembling
1. Engine
2. Gasket (1140-13141)
3. Gasket (T2075-14120)
4. Carburetor SET (585879701)
5. Air-funnel (848ES08300)
6. Spacer (1142-83110)
7. Bolt (8488455000)
Fig.1
G320PUM

6
Engine Mounting
Make sure that the engine is to be mounted according to the instruction manual
provided by model boat manufacturer.
In case such instruction manual is not available, make sure that the engine should
be mounted at least by 4 points both at engine's PTO side and recoil starter side.
[ Note ]
1) Be sure to set flat washers or metal plates on the reverse side of the
mount to prevent bolts from sinking into the mount.
Be sure to check if the bolts are securely fastened.
2) The fuel head between carburetor and the bottom of fuel tank must be less
than 100 mm (4 inches)

7
The exhaust system (e.g., muffler) is not equipped with this engine as standard.
When you select the exhaust system, check the engine speed (rpm) when the
maximum output is generated by using the exhaust system you are going to select.
And then decide the appropriate screw-propeller that would meet such engine
speed (rpm) that the exhaust system requires.
In general, contact your boat manufacture to select appropriate screw-propeller and
exhaust system.
Screw-Propeller and Exhaust System

8
•Mix gasoline (octane over 95) and high grade 2 cycle engine oil (mixing use
type; JASO FC grade or ISO-L-EGC grade) at mixing ratio 25:1.
•The mixing ratio is according to the oil recommendation.
[ NOTE ]
1) Gasoline may contain maximum of 10% Ethanol (grain alcohol) or up to 15%
MTBE (Methyl tertiary-butyl ether).
Gasoline containing Methanol (Wood Alcohol) is NOT approved.
2) Gasoline is very flammable. Avoid smoking and any fires near fuel.
3) To prevent all possible problems on fueling system, make sure to use the fuel
filter which has more than 300 mesh or equivalent and gasoline proof rubber
pipe or equivalent.
Incorrect fuel filter may cause engine trouble like fuel passage stuffing in
carburetor, or piston surface scratching etc.
4) When fueling, make sure that no fuel touches the hot parts.
5) Assemble the fuel line so that it does not touch the hot parts. Also, check that
there is no fuel leakage due to cracks, or hardening.
Fueling System

9
How to Stop The Engine
●How to start
a. Fill the fuel tank with the fuel.
b. Push the priming bulb upper the carburetor until fuel appears in the priming bulb.
c. Choke the engine and open the throttle valve approximately 1/4~1/3 of the full
open position.
d. Quickly pull the starter cord until the initial combustion noise is heard.
e. When the initial combustion noise is heard, open the choke, set the throttle valve
at the idle position or at the position slightly open from the idle position and
quickly pull the starter cord a few more times. Then the engine starts.
Starting
For stopping the engine, the red lead wire
from the coil should be grounded to the
engine body, or the throttle valve should be
closed completely.
Red
Lead
Black
Lead
Kill Switch

10
Carburetor Adjustment
The carburetor is provided with 3 adjust screws they may need a little adjustment
depending on the temperature, atmospheric pressure (altitude), and an exhaust
system, etc. of the area where the engine is used. Start the engine without making
any adjustments. Make readjustments only when the engine shows any mal-running.
Standard opening at the begining of each needle as follows;
Low Speed needleHigh Speed needle
Idle Screw
HL
1 7/8±1/41 3/8±1/4

11
Carburetor Adjustment
Idle Screw:
Turning this screw clockwise increases the idling R.P.M. Turning it
counterclockwise decreases the idling R.P.M
Low Speed needle:
This is the fuel adjust screw (not the air screw). Turning this needle clockwise
makes the mixture gas leaner and turning it counterclockwise makes it richer.
Set this needle at a position which is 1/4 open from best mixture (maximum
R.P.M.) position.
High Speed needle:
Turning this needle clockwise makes the mixture gas leaner and turning it
counterclockwise richer. Set this needle at a position which is 1/8~1/4 open
(counter clockwise) from the maximum R.P.M. position.
1. Do not tighten the High and Low Speed needles too firmly.
2. When the unit has just started and the engine is not warm enough, there
may be insufficient acceleration and the engine may be stopped. Be sure
to perform idling before operation.
CAUTION

12
Engine Break-In
Operation
No specific break-in is required.
The engine is gradually broken-in as it is used and the output is also gradually
increased.
For checking the whole conditions of the boat, it may be better to operate the
engine at slow RPM for 1/3 tank and mid-high RPM for 2/3 tank.
•The engine is already tuned up to get high performance, and needs correct
maintenance to keep such high performance.
•The details of operating model boat shall be provided by model boat
manufacturer.
•Always keep the engine well according to the Maintenance clause described in
this owner's manual.

13
Maintenance
1) MAINTENANCE CHART
Before Every Every
Items Action Use 25 hours 100 hours Note
Leakage, Check ✔✔✔
Damage/Crack
Idling Speed Check/Adjust ✔✔✔
Spark Plug(gap) Check/Adjust ✔✔Replace if necessary
Cylinder(barrel) Check/Cleaning ✔✔ ↑
Piston, Ring Check/Cleaning ✔✔ ↑
Muffler & Bolt Check/Cleaning ✔✔✔ ↑
Bearings Check/Cleaning ✔✔ ↑
Crank Shaft Check/Alignment ✔↑
Rotor Check ✔✔ ↑
Water Jacket Check/Leakage ✔✔✔ ↑

14
Maintenance
2) SPECIFICATIONS AND TECHNICAL DATA
Items Unit G320PUM Remarks
Bore x Stroke mm 38 x 28
Displacement cm331.8
Effective Compression Ratio 9.7
Type Walbro WT
Carburetor Venture(mm) ø13.5
Starting Recoil Starter
Type CDI
Ignition Timing BTDC 30°/7000rpm
Standard CMR7H NGK
Option(Hot Type) CMR6H ↑
No load max Speed rpm 20000
Idling Speed rpm 4000
Max. Net Power kW/rpm 3.31/14000 Without muffler
Max. Net Torque N.m/rpm 2.35/10000 ↑
Carburetor H 1 7/8 ± 1/4
Standard Opening L 1 3/8 ± 1/4
Spark Plug

15
3) MAINTENANCE SPECIFICATIONS
G320PUM
Items Standard Limit Measuring Device Remarks
Bore (mm) ø38 Plating damaged Eye Checking
Diameter (mm) ø37.97 ø37.87 Micro Meter
Piston Ring 1.01 1.11 Thickness Gauge
Groove width (mm)
Piston Pin Hole (mm) ø9.01 ø9.05 Cylinder Gauge
Clearance between
Piston and 0.03~0.06 0.15
Cylinder (mm)
Clearance between
Groove and 0.02~0.04 0.1 Thickness Gauge
Piston Ring (mm)
End Gap (mm) 0.1~0.3 0.5 Thickness Gauge
Width (mm) 0.98 0.93 Micro Meter
Piston Pin Diameter (mm) ø9 ø8.98 Micro Meter
Connecting Rod Small end (mm) ø12 ø12.05 Cylinder Gauge
Crankshaft Dia. at Main Bearing (mm) ø12 ø11.98 Micro Meter
Eccentricity (mm) — 0.07 Dial Gauge
Axial Play (mm) — 0.5 Thickness Gauge
Gritty orr
Main Bearing — —
Feels Flat Spot
At the skirt end and
the right angle to the
piston pin.
When inserted in
a new cylinder.
Piston
Cylinder
Piston
Ring
Micro Meter
Cylinder Gauge
Maintenance

16
Maintenance
4) CARBURETOR
Items Standard Limit Measuring Device Remarks
Metering Lever set (mm) 1.65 ± 0.16 Vanier
Inlet Valve Opening Pressure (kg/cm2)1.3~2.3 Leak Tester
Inlet Valve Closing Pressure (kg/cm2)0.7~1.7 Leak Tester
5) IGNITION SYSTEM
Items Standard Limit Measuring Device Remarks
Spark Plug Air Gap (mm) 0.6~0.7 0.7 Thickness Gauge
Ignition Coil/Flywheel Air Gap (mm) 0.5 0.6 Thickness Gauge
1.76 kΩ—Sparkplug Wire – Stop Core
Coil Resistance (Ω)294 Ω—Volt Meter Stop Core – Coil Core
1.46 kΩ—Coil Core – Sparkplug Wire

17
Maintenance
6) TIGHTENING TORQUE
Items Screw Size Standard (N·m) Limit (N·m) Remarks
Carburetor M5 (P=0.8) 3.4 2.9~3.9
Insulator M5 (P=0.8) 4.4 3.9~4.9
Pully Assy M8 (P=1.0) 12.7 9.8~14.7
Cylinder M5 (P=0.8) 7.9 6.9~8.8
Crankcase M5 (P=0.8) 5.8 4.7~6.9
Spark Plug M10 (P=1.0) 10.8 8.8~12.8
Muffler M5 (P=0.8) 8.8 6.9~9.8
Ignition Module M5 (P=0.8) 6.4 4.9~7.8
SO Coil M4 (P=0.7) 1.8 1.5~2.0
Recoil Starter M4 (P=0.7) 1.8 1.5~2.0
Water Jacket M3 (P=0.5) 1.5 1.0~2.0
Mount Plate M5 (P=0.8) 3.9 3.4~4.4
Cover, TR M4 (P=97) 1.3 1.0~1.5
Apply Three Bond TB1342H
(Low Strength) or Equivalent

Part Name Part No. External Appearance Usage
1Puller Assy 577409701 To remove rotor.
2Piston Stopper 4810-96220
3Hex Wrench 3304-97611
4Snap Ring Pliers 5500-96110 To remove snap ring.
5Puller 581965501 To remove pulley assy.
To hold crankshaft when
disassembling/assembling
the rotor.
For socket screw of
4mm, 5mm and 6mm.
18
Special Tools

19
Service Guide
Puller
(14mm Hex.)
Piston Stopper
1. REMOVING ROTOR
1) Remove the spark plug, fit the piston stopper
(P/N: 4810-96220) into the cylinder.
2) Remove the pulley assy by puller (P/N: 581965501)
and ratchet. (Fig.2, Fig.3)
3) Remove the rotor using puller assy (P/N: 577409701).
(Fig.4)
Fig.2
Puller
Pulley
Assy
Fig.3
Puller
Assy
Fig.4

20
2. ASSEMBLING ROTOR / IGNITION MODULE (Fig.5)
1) Insert the 0.5mm plate in between the rotor magnet
metal and the coil iron core.
2) Tighten bolts (M5x2) while pressing the ignition
module toward rotor.
3) Remove the 0.5mm plate and confirm that the air gap
is 0.5~0.6mm by thickness gage.
3. REMOVING PISTON PIN (Fig.6)
1) Remove snap rings from both sides of the piston pin.
2) Push the piston pin by socket.
Service Guide
Bolt (M5)
Ignition
Module
Rotor
Plate
Fig.5
Piston
Pin
Socket
Fig.6