Roto 125 FS User manual

TOP FOUR STROKE ENGINES
ROTO 125 FS
OPERATING INSTRUCTIONS
OPERATING INSTRUCTIONS

ROTOmotor Ltd., Czech Republic - Europe ROTO 125 FS ROTOmotor Ltd., Czech Republic - Europe Operating instructions
ROTOmotor manufacturer of top four-stroke engines Page:2
CONTENTS
1. Introduction .................................................. 3
2. Safety instructions .......................................... 3
3. Package contents ........................................... 4
4. Mounting ..................................................... 5
4.1 The engine mount ...................................... 5
4.2 The engine ............................................. 5
4.3 Carburetor .............................................. 6
4.4 Fuel system ............................................ 6
4.5 Waste output ........................................... 7
4.6 Exhaust pipes .......................................... 7
4.7 Propeller installation .................................... 8
5 Ignition ...................................................... 10
5.1 Ignition installation .................................... 10
5.2 Ignition power supply .................................. 10
6 Engine lubrication ............................................11
7 Settings ...................................................... 12
7.1 The valves adjustment ................................. 12
7.2 Carburetor settings .................................... 14
8 Starting the engine ......................................... 15
9 Spare parts .................................................. 16
10 Accessories ................................................. 17
11 Warranty card ............................................... 18
12 Contact / technical support
VERSION 2.6/ENG
Please check the updates of the operating instructions on the website www.rotomotor.cz so that your engine always has the best care.

ROTOmotor Ltd., Czech Republic - Europe ROTO 125 FS ROTOmotor Ltd., Czech Republic - Europe Operating instructions
ROTOmotor manufacturer of top four-stroke engines Page:3
Thank yOu FOR chOOSing OuR pROducT
FOuR-STROke engine
pROduced in The czech Republic.
Introduction
You have purchased a new four-stroke two-cylinder petrol engine that requires the rst few
important steps to successfully start your RC plane model .
The engine has already been tested and started by the manufacturer, everything is ne and
it works as it should!
The engine is basically adjusted and tested with a 28/10 propeller tting and ROTO FS
exhausts.
• Always be very careful when handling the engine.
• The engine can start even when the propeller rotates very slowly and injure you!
• Whenever you start the engine, make sure that you have the model secured so that
there is no movement of the model and possible injury!
• Do not drive the plane with the engine running in between spectators and colleagues
at the airport!
• Do not touch the engine after the ight, it is hot and there is a risk of burns!
• You have one body, take care of it and enjoy ROTO engines.
1.
Safety instructions2.
ADVICE WARNING

ROTOmotor Ltd., Czech Republic - Europe ROTO 125 FS ROTOmotor Ltd., Czech Republic - Europe Operating instructions
ROTOmotor manufacturer of top four-stroke engines Page:4
Please follow the instructions carefully.
Check that all the listed parts are in the box.
Standard package contents:
1. ROTO 125 FS................................ 1 x
2. Ignition ROTO 125 FS....................... 1 x
3. Exhaust pipes .............................2 x
4. Waste oil hose ............................. 1 x
5. Spark plug key CM6 ........................ 1 x
6. Cable ties ..................................4 x
7. Silicone tubes .............................2 x
Package contents3.

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Mounting
4.1 The engine mount
After mounting the engine firewall
occasionally to prevent loosening.
4.2 The engine
It is necessary to provide enough air for the supply to the carburetor. In case of lack of a air, the
engine may have poor performance and may uctuate at maximum speed.
It is necessary to ensure sucient cooling of the cylinder heads and cylinders with a constant
supply of air from the propeller or from the surrounding environment.
To mount the engine in the model, we will use steel strength bolts and lock nuts.
We will use large washers under the nuts due to the pressure distribution on the engine mount,
so that mount is not dented.
For the engine to work properly and its properties to be optimal, the engine must be warmed
up to operating temperature.
The carburettor is set at the factory (ROTOmotor). We do not recommend any disassembly of
the intake manifold or carburetor.
4.

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4.3 Carburetor
Do not remove the nozzle, do not modify it!
It‘s part of the engine, and the correct
operation of the engine depends on it.
A suction nozzle is mounted on the carburettor. We must ensure a sucient air supply for the
correct operation of the engine. Do not cover it!
4.4 Fuel system
It is necessary to connect a hose with fuel supply to the carburettor. A protective plug is atta-
ched to the carburettor fuel tting due to dirt during transport. This plug must be removed
and the gas supply from the model‘s tank connected in its place.
When removing the engine from the model for a longer period of time, it is necessary
to replace the protective plug to prevent the fuel in the carburetor from drying out.
The image is for illustration purposes only

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4.5 Waste output
NO TOOLS ONLY HAND LOCTITE 326
Then install the lubrication waste oil hose on the rear cover of the engine. To seal it we use
Loctite 326 glue or similar to seal the thread.
WAIT
3HOURS
We recommend leading the waste oil hose to the landing gear.
Waste output is very important and must never be blocked.
In any case do not reduce the diameter of the hose, or it will damage the engine.
If the waste output was clogged, the motor will be damaged.

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4.6 Exhaust pipes
The exhaust pipes are made so that they can be rotated around the axis. Therefore, set the
exhaust pipes to the desired position by turning and then secure by tightening the nut.
The exhaust pipes can be
rotated in a small range as
needed.
*A part of the package
± 10°
Beware of damage to the end of the pipe!
The end of the pipe serves as a sealing surface for the
extension tube. If damaged, it will not be possible to
seal the pipes correctly!
The diameter of the exhaust
pipe cannot be reduced!
Silicone pipes* are used to seal the transition between the exhaust pipes and the ROTO
exhausts, or between the extension pipe and the ROTO FS exhaust.
ROTO extension pipe and exhaust not included!
When mounting on the extension pipe or exhaust, the silicone pipe* must be secured with
a cable tie* on each side of the hose to seal the connection well.
There should be no more than 2mm
between the end of the exhaust pipe
and the exhaust.
The silicone pipe seals correctly only if the con-
tact surfaces are clean and free of grease.
When reassembling, the contact surfaces must
be degreased!

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4.7 Propeller installation
It is very important to mount the propeller correctly. 6 strength screws are used for this
purpose. Tighten them evenly! The propeller must be regularly checked and tightened, espe-
cially when using a new wooden propeller.
Check the tightening of the propeller often, especially at beginning, when the
propeller is new!
Loose screws will cause the screws cuts to, exposing you to the risk of injury
as well as damage to your model. This danger is mainly posed by the use of a
wooden propeller.
Direction of rotation of the propeller / Engine

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Ignition
5.1 Ignition installation
Never remove the Hall sensors from the backplate.
5.2 Ignition power supply
The recommended power supply for ignition is 4-9V.
Always charge the batteries before ying.
Do not rely on charging from the last ight!
Ignition installation is an integral part of installing an engine in an aircraft.
Place the ignition in a suitable place where there is no risk of excessive heat from the
cylinder heads or the exhaust system.
If the ignition is heated above 60 °C, the ignition will switched off and the engine stops
working.
Make sure that the ignition is
well and suciently cooled!
Make sure that the connectors are
tted correctly and that there is no
risk of loosening them!
Do not bend the HV cables into sharp
bends, they may be interrupted!
Install the spark plug cup from the ignition to the spark plugs.
5.

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Engine lubrication is provided by adding oil to gasoline in a ratio of 1:50.
For easier application, use this table:
Fuel Oil
L ml
1 20
2 40
3 60
4 80
5 100
6 120
Use gasoline 95 - 98 okt.
+
Failure to follow the recommended oil types will void your warranty.
! DANGER OF ENGINE DAMAGE!
Information about our network of dealers at [e-mail]
Engine lubrication
Fuel Oil
gal oz
1 2.56
25.12
37.68
4 10.24
5 12.8
6 15.36
Metric system Imperial system
Motul 800 oil /1:50 or STIHL HP Ultra oil /1:50
6.

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Settings
First cylinder head
Second cylinder head
Top Dead Center Top Dead Center mark
7.
7.1 The valves adjustment
For the operation and long-term operation of the engine, the correct valve clearance must be
checked after the rst 2-3 hours of operation.
Follow these steps to check and adjust:
Unscrew the rocker arm cover bolts on the cylinder heads and then remove the rocker arm
covers. Adjust the piston to the top dead center so that the mark on the propeller hub is in
alignment with the crankcase dividing plane of the engine on the top of the engine.
Then start adjusting the clearances on the side where the valves are not cut shear! This means
where there is a slight clearance on both rockers.
Valves adjustment:
Loosen the lock nut with a wrench and turn the screw. Set the required clearance with the help
of a feeler gauge.
Then tighten the lock nut again and proceed to adjust the second valve.
Repeat this on the other side of the engine, turning the crankshaft 360 °.
Then complete the engine.
Rotates counterclockwise
Now the rocker arm clearance is adjusted. Future adjustments are only necessary
when disassembling certain important parts.

Tightening torque
Spark plug..............................................20 Nm
Rocker arm cover................................ 2,2 Nm
Rocker arm ..............................................2 Nm
Cylinder head..........................................5 Nm
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Adjusting the first cylinder head
Adjusting the second cylinder head
Valves adjustment
Suction valve .................................. 0,1 mm
Exhaust Valve ................................ 0,2 mm
4
2
E S
S E
1
3
1
2
3
4
S
E
If you have no experience with this type of engine adjustment:
1. Pack the engine and send it for adjustment to your specialist garage, where
the engine will be adjusted for you.
2. Ask the manufacturer by email at [e-mail]

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H needle
L needle
Stop screw
The carburetor is factory adjusted and should NOT need an adjustment before a rst ight.
Should you wish to adjust the carburetor after the Run-in period and ne tune it to the prop
of your choice, please use the following procedure.
Set the High needle „ H „ for the highest RPM. After you are satised with High-end, adjust
the Low „ L „ needle for smooth transition between High and Low range with out any hesi-
tation.
Adjusting servo / idle
The idle speed is set to 1200 ± 200 RPM by the deection at the servo.
Then you can remove the stop screw.
How do we know that the engine is set correctly?
With the propeller 28/10 the engine achieves - 5800 ± 200 RPM. When properly adjusted, the
engine continuously accelerates from idle speed to maximum. The idle speed with a 28/10
propeller is 1,200 ± 200 RPM
These gures may dier when using a dierent propeller.
7.2 Carburetor settings
The image is for illustration purposes only
The motor has been adjusted on the bench. Must be loosen the
stop screw to avoid damaging the servo.
ROTO recommends removing Stop Screw and idle rpm keep by your TX

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Always check that the ignition is off
Starting the engine
We will perform a cold start according to the following instructions:
After ying, do not run out remaining fuel from the aircraft tank.
System will be vented and the engine will start incorrectly.
Switch on the carburettor choke and, if possible, at the same time plug the carburettor intake
with your nger so that the engine intake effect is maximized. Rotate the propeller about ten
times and then release the carburettor intake, turn off the choke valve, turn on the ignition and
start the engine without the choke. We will only use this when the fuel is rst drawn from the
tank into the carburetor.
Allow the engine to warm up to operating temperature and run the engine for 15-20 minutes
with occasional throttle.
Then ne-tune the carburetor to the exhaust system used and propellers. Use the needle mar-
ked „H“ to ne-tune the maximum engine power and the second needle with mark „L“ to adjust
the engine transitions to maximum speed.
The idle speed is set by the throttle servo on the transmitter.
For warm engine starts it is good to use a starting system without a choke
Remember to check the correct function of the on-board system before each
start by testing the range of the transmitter.
The rst way to start:
8.

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Spare parts
03-0127 .....................................................Propeller center bolt
03-0128 .....................................................Prop washer
03-0148 .....................................................Carburetor bolt
03-0180 .....................................................Air intake - long
03-0415 .....................................................Gasket set
03-0715n ....................................................Tappet rod
03-0744 .....................................................Carburetor insulator
03-0148 .....................................................Carburetor bolt
03-0761PS ...................................................Mainfold
03-0772 .....................................................Exhaust pipe
03-0777 .....................................................Sawox servo holder
03-0780 .....................................................Choke control lever
08-0008 ....................................................Ignition system
N0011 ........................................................Spark plug CM6
N0279 .......................................................Carburetor
03-0360 .....................................................Spark plug key
9.

ROTOmotor Ltd., Czech Republic - Europe ROTO 125 FS ROTOmotor Ltd., Czech Republic - Europe Operating instructions
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03-0400A ...................................................TS muer set 85 & 125 FS
03-0589 .....................................................Connector FS 200mm
03-0596 .....................................................Connector FS 300mm
03-0620 .....................................................Muer STANDARD FS
06-0110 .....................................................Propeller drill jig
Accessories
03-0415 ..................................................... Gasket set
10.
Muer STANDARD FS
• Push rod tube O-ring ............ 8x
• Carburetor gasket ............... 2x
• Rocker cover gasket ............. 2x
• Cylinder gasket .................. 2x
• Cylinder head gasket ............ 2x
• Manifold O-ring.................. 2x
For more info visit www.rotomotor.cz
Propeller drill jigTS muer set 85 & 125 FS
Connector FS 200 & 300

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Warranty card
Name of a product:
Type:
Serial number:
Date of purchase:
Dealer’s name, address:
Stamp:
11.

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This product has been tested, inspected and inspected for sale for 24 months
from the date of sale.
The warranty covers defects that occurred during the warranty period due to an
error in the production or materials used.
In the event of a defect, please report the product together with the sales docu-
ment and this, completed and conrmed, warranty card either to the seller or send
the product to the manufacturer.
Attach a description of the defect or how it occurred to the warranty claim.
The right to a free warranty repair expires in the following cases:
►the warranty does not cover defects caused by incorrect installation (eg incorrect
installation, insucient cooling, etc.)
►if the data on the warranty card and sales document dier
►the product has been used for purposes other than those for which it was intended.
►the warranty does not cover normal wear and tear or unauthorized intervention
►damage caused by dirt or when electronic or otherwise sensitive parts of the engine
come into contact with water or chemicals (eg paint, cleaning agents, etc.)
►with regard to a defect caused by mechanical damage to the product (eg model
accident, engine disassembly, etc.)
In the event of an unjustied complaint, the customer will be charged for all costs
associated with this complaint, including any repairs.
The costs associated with the transport of goods to the service are borne by the
customer
The costs associated with the transport of repaired goods under warranty are borne by
the manufacturer. Warranty repairs are performed only by the manufacturer
ROTOmotor accepts no liability for injuries, damage to health or property, when using the en-
gine in violation of the operating instructions manual, the use of common safety principles for
the use of the combustion engine and its accessories.

Developed in the
Czech Republic
ROTO engines Ltd.
Zbecnik 259
Hronov 549 31
Czech Republic
FOllOw uS On SOcial media
[e-mail]
[phone]
www.rotomotor.cz