Nitro RC Twin Cylinder 4 Stroke RC Engine Beginners Guide | Stirlingkit

Nitro RC Twin Cylinder 4 Stroke RC Engine Beginners Guide | Stirlingkit

Nitro RC Twin Cylinder 4 Stroke RC Engine Beginners Guide | Stirlingkit

Still looking for the Ideal entry-level nitro engine kits to build? As the Christmas holiday is around the corner, some of you might consider buying some gifts for your kids or nieces. You might sometimes find it hard to buy something for yourself, especially for multi-children families. Consider this, Stirlingkit has got a killer line-up in our 2022 Engine Gift-Giving Guide, which is the Otto Motor FS-L200AC engine, a 2-cylinder 4-stroke engine kit just for someone like you with a cool motor head. Just only 149.99usd, make your dream come true to have a memorable motorhead holiday.


How to Build & Setup Your Nitro Twin Cylinder Engine?

Follow Johnny Q90‘s video, you will find it's easy to find basic steps to build and set up your Nitro Engine. It's an absolutely pefect model engine for a desk of the young car enthusiast.



For the sake of safety, it is strongly recommended not to disassemble the engine and start the mechanism. If any starting problems, please contact your local dealer or OTTO technician to solve them. If return to the factory for testing, OTTO will provide you with high-quality after-sales service.

If any problem caused by unauthorized disassembly, you will bear the corresponding responsibilities

and expenses

1 Glow plug

Model FS-L200AC-OT requires 2 special glow plug for a four-stroke methanol engine, which is started by using 1.5 volt power supply. When the battery is disconnected, the heat retained in the chamber is still enough to heat the filament to keep the engine running. When top center compression position is reached, an "automatic" ignition burst is achieved, while the spark plug remains at high temperature, allowing for higher rotational speeds while the load is reduced. In contrast, if the RPM is low, the spark plug will cool, and if the RPM is too low, the ignition will stop, and then the engine will stop. Therefore, you can control the engine speed by adjusting the damper to achieve the best effect you want.


Please use quality guaranteed methanol model engine fuel. Self - dispensing or counterfeit fuel will greatly reduce the performance and life span of the engine. Since it is a four-stroke engine, in order to ensure the normal operation of the engine, we require the only 20-25% nitro methane fuel can be used. If high nitro fuel is used, the ignition time and cylinder pressure of the engine will be greatly affected, and the normal and stable operation cannot be maintained.

When the nitro content of the fuel increases or the brand of fuel change , it is recommended to use oil-rich needle adjustments to run the engine so that the optimal setting for the new fuel can be rechecked, (please adjust the ratio of gasoline fuel to 1:25 to 1:30, and use 2T engine oil).


If the engine is running at very high speeds and on high nitro fuel,The life of the spark plug does not last long. Please note that engine fuel is toxic. Keep it out of contact with eyes or mouth and always store it in a clearly marked container and place, and keep out of reach of children. It is highly flammable. Keep away from open fires, overheating or any source of


3.Fuel tank

It is recommended to use a 100cc tank. The tank should be installed on the same flat as the engine.

The gap between the fuel inlet & outlet of the fuel tank and carburetor should be kept within 1 cm (the carburetor must be higher than the fuel inlet & outlet of the fuel tank). If the gap is too high, the carburetor's working efficiency will be reduced and the engine will be started adversely. To ensure clean fuel supply, pls use standard 5mm silicone tubing and properly install oil filters. Since the engine itself relies on negative pressure to absorb oil, it is recommended the muffling exhaust pipe can be used to pressurize the fuel tank

4.Start power supply

The series FS-L200AC-OT has been installed with a start motor, which can be started with one button. You only need to purchase standard 7.4v 25C lithium battery to realize quick start. Too low or too high voltage of starting battery will not guarantee the service life of the starting

motor, do not use incorrect voltage starting battery

5.Environment for starting

Please start the engine in an open, airy environment to avoid discomfort from burning gases

6.Platform for Starting

Since the engine will produce some vibration after starting, please place it on a stable and flat platform

7.Heat dissipation

Since the engine has been cooled by a fan, high-speed rotating fan blades will be dangerous,do not touch. If you find cracks in the blade during use, please replace in time


Every time you start the engine, please carefully check whether there are cracks in the blades.

we must replace new if any cracks to avoid the danger of blade spread out during high-speed



 Q: Did anyone fit the gas conversion kit into an L200-AC? I've got as far as assembly the L200 with the different flywheel with the 2 magnets. The flywheel had 2 slots cut in for the pin 90 degrees apart - I guess this is so you can either mount the hall effect sensor at the bottom or side? I'm new to these but is it just as case of making sure 1 magnet aligns with the hall effect sensor as a piston reaches top dead centre? i want to know the different positions the flywheel can be fitted and also the relative position of the hall effect sensor.

A: There is no fixed position to install the hall, customers need to fix it according to their own needs, because not everyone will buy the base, we use this metal sheet to fix the hall. The installation position of the hall needs to be fixed by yourself if you have not purchased the Metal Fixing Base for SEMTO ENGINE ST-NF2 / TOYAN Single Cylinder Engine FS-L200, and it is not easy to unify the fixed position. It is recommended that you hire a small iron piece to fix it as shown in the picture below.

Generally, we use to fix the Hall on the bottom, and use an iron piece like the one shown below to fix the Hall. The best ignition setting for a four-stroke engine is when the piston completes the compression stroke and is about to enter the power stroke. The magnet and the Hall first Second induction ignition.


7.  How much torque I should use for tightening? 

 Torque specification reference (unit N*M):
M2 0.333
M2.5 0.73
M3 1.38
M3.5 2.15
M4 3.12




Four-stroke engines have stronger torque output than two-stroke engines, so the corresponding measures should be taken during operation

In order to extend the service life and improve the performance, each engine has been tested at

the factory. You need to do proper running-in and cleaning after receiving the engine. After

continuous running in, the cylinder pressure will be gradually strengthened. Due to the high

simulation degree of this engine and the large number of various parts, we do not recommend

you to fully disassemble the engine, we will provide a variety of effective sales to help you

maintain and stable use

  1. Check the timing belt and CAM axle box

Please make sure that the marking points on the two pulley can be down at the same time,see P43.

Open the hood and add the grease. Since the mounted CAM is used, please add the solid grease to ensure

stable operation and avoid dry friction of the CAM.

  1. Check the power supply

Please confirm that the voltage of 7.4v universal ignition power supply is normal, and full

of electricity

  1. Initial Oil Needle Setting

The prerequisite is adequate lubrication and cooling. The engine is run with very important oil

needle settings: The excess oil not only provides rich lubrication, but also conducts heat from

the surrounding metal and further assisted by the fuel nitro methane. the two-stroke model engines in pre-heating into the cylinder through the crankcase on a longer trip. But The four-stroke engine, with its intake pipe and carburetor mounted high on the cylinder cap, means that the rich mixture of cooling fuel and air will flow directly into the cylinder directly.With the help of fan cooling, it can provide excellent operation experience for every enthusiasts. You can also buy the OTTO series of water cooling accessories, so that your engine will be able to maintain stable operation for a long time.


When leaving the factory, each engine has completed the oil needle setting. If you have misadjusted the oil needle during the use, it is recommended to adjust the main oil needle to 2.0 laps and the auxiliary oil needle to 1.5 laps. Since the methanol engine needs to maintain the temperature of the spark plug filament to achieve ignition, when the engine is in the oil rich state for a long time at low speed, the temperature of the filament will gradually reduce, resulting in ignition difficulty. Therefore, it is necessary to up the speed for cleaning oil at intervals to avoid oil enrichment at low speed


Please keep the throttle opening larger than 1.5mm

Loosen the throttle screw and adjust the size of the throttle

  1. Start


It is important to put the throttle in the right position before starting the engine. It is recommended that the throttle be opened at 30% to start, the engine is not allowed to open the throttle too far under "no load" conditions, which can quickly overheat and can seriously damage the engine piston ring and cylinder sleeve.

Connect the spark plug battery and press the start button. Once the engine starts, disconnect the spark plug battery and keep the engine running slowly under the oil-rich needle setting. (If necessary, gently adjust the throttle lever to keep the engine idle steady.)

Since a four-stroke engine requires a lot of air intake, it is important to set throttle screws , the minimum throttle opening (idling setting) is about 1.5mm.,For the use of all kinds of engine enthusiasts. do not use a strong force to twist the throttle valve screws to adjust the size of the throttle door opening, but using valve screws to loose throttle, and then pull the throttle rocker arm to adjust. As shown in figure

The prerequisite is adequate lubrication and cooling. The engine is run with very important oil needle settings: The excess oil not only provides rich lubrication, but also conducts heat from the surrounding metal and further assisted by the fuel nitro methane. the two-stroke model OTTO Motor

If the engine stops, cooling it for 15 seconds before restarting. Please hold down the start key within 5 seconds for each start, so as to protect the start motor life. Allow the engine to warm up for 30 seconds after starting so that the oil in the fuel can be fully lubricated to each working part. When the engine rapidly drops from high speed to low speed, or when low speed rapidly rises to high speed, the engine is unstable or the throttle control is slow or flashover, please confirm the carburetor working status

Rich oil

When the engine has more fuel , smoke is emitted or accelerates slowly, indicating that the engine has excessive oil, please turn the main oil needle clockwise, 15° as a unit, gradually reduce the main oil needle, until the sound of engine exhaust is soft and strong, and the exhaust pipe slightly smokes and the lubricates fuel spray out

Lean oil

If the sound of the engine is too sharp, like the sound of dry friction between metals, the temperature rises rapidly, and the engine is stopped immediately after acceleration, indicating that the engine has low oil, please turn the main oil needle counterclockwise, 15° as a unit, gradually reduce the main oil needle, until the sound of engine exhaust is soft and strong, and the exhaust pipe slightly smokes and the lubricates fuel spray out

Idling Stop

When the engine speed changes rapidly, suddenly adjust from the high speed to the low speed, the flameout occurs, please confirm whether the throttle is closed less than 1.5mm, or gradually reduce the auxiliary oil needle, (clockwise rotation) gradually adjust the auxiliary oil needle, 20°as units, until the engine maintains a steady idle speed. In the debugging process, the auxiliary oil needle should not be excessively reduced, so as not to cause engine have lean oil, we recommend that the minimum value of auxiliary oil needle should not be less than 1 turn.



The series of FS-L200AC is a very precise machine that you need to clean timely. Due to the impact of environment and the fuel when using, the engine parts have a certain amount of wear and corrosion. So, OTTO will also provide you with long-term maintenance services. You can also complete the basic cleaning and maintenance

Carefully clean the carburetor and remove dirt and grease from the inlet

If an air filter is used, make sure the filter is clean and free from blockage

Recommended that the air core used for more than one hour should be replaced in time.

Be careful to remove contaminated filter elements to ensure that dirt does not enter the carburetor

Do not remove timing synchronous belt, you can use alcohol as a cleaning agent to wipe the belt. Do not use corrosive detergent to clean synchronous belt, to avoid damage

Glow Plug must be treated as consumables. Long running glow plug will not ensure the normal operation of the engine and you can extend its life maintain the performance of the engine if you use it carefully,

Use appropriate tools for disassembly for Your FS-100AC


Use fuels containing a moderate percentage of nitromethane

Do not overtilt the engine and do not connect the battery while adjusting

The time to replace the glow plug. expect burned, It also need to be replaced on these situations because it no longer provides optimal performance,

For example:

a.The surface of the filament becomes rough and white

b.Filament curl deformation

c.External material adhered to the filament or plug corrosion

d.The engine will power off when idling

e.The power went out after the engine started

At the end of each operation, empty the fuel tank, energize the glow plug, and try torestart the engine to burn the possible left fuel in the fuel tank. Repeat this process until the fuel is cleared from the engine.

Inject some antiseptic oil and briefly start the motor to distribute the oil to the working parts. Do not inject this oil into the lubricator nozzles, as this may cause the O ring of the carburetor to deteriorate Add solid lubricant to camshaft and valve tappet to ensure that the CAM axle box has enough lubricant for each operation


These maintenance programs will be stored after a period of time, and there is a risk of corrosion or startup difficulties, if you need someone to deal with, please contact us

Replacement of running parts

After long-term operation, the friction between the engine components will cause wear and too large gap, the replacement of related parts will help you maintain your engine better. When you are in the process of use, there is not flexible start, power reduction, idle speed instability and so on, please feedback your usage process and poor performance of the engine to the local dealer or OTTO, we will serve you wholeheartedly. Parts replacement, we will provide professional equipment and experienced team. Please do not disassemble the engine without professional tools to avoid the risk of uncontrollable damage to the engine



If the engine fails to start, check the following carefully:

Whether the battery voltage is normal, whether the power is full

Whether the glow plug has failed

Whether the fuel can reach the carburetor smoothly

Do not start the engine when it is flooded. Remove the glow plug, close the oil needle and press the start button to drain the excess fuel. (Cover the plug hole with a piece of woolen cloth so that the fuel doesn't spill on you.) If forced to start without removing the excess fuel, it may cause irreversible damage to the starting system, as well as the connecting rod and crankshaft to strain and deformation

Timing belt adjustment

All OTTO Motor have been tested for timing belt position before they leave the factory.

After several hours of execution, the operating power loss or engine running instability is found, the timing belt needs to be tested and adjusted to get the correct ignition information for the engine. Please check against page 11 of "timing belt timing diagram"

When Turn off at low speed, do not keep it at too low speed a long time. Since the methanol engine needs to maintain the temperature of the spark plug filament to achieve ignition, when the engine is in a rich state for a long time at a low speed, the temperature of the filament will gradually decrease, resulting shutdown. Therefore, it is necessary wait a while to up the speed oil and clean the oil to keep the temperature of the filament


Common Questions People Might Ask


1. how about the durability of these miniature engines?You could do some testing on that. I'm always afraid of buying those for a model car and the engine breaking beyond repair after a couple of runs.

Answer: You don't need to worry about quality issues, as we have several examples of modified model cars, and they are all very successful, as long as they are maintained carefully after usage.

2. why did JQ 90 choose 30% nitro on this engine when Toyan calls for 20-25 % and what % of oil do he use in his nitro mix . Does he use 30% in his FS L200 also ? 

Answer: We have many years of modeling experience and believe that the best methanol fuel is 20% castor oil + 5-30% nitromethane + the rest is methanol. This ratio is the best performance we have tested

3. Hello, why don't you place a gasket between the lower two parts of the engine block? Also, what is the brand and type of your torque screwdriver please? Nice air-cooled four stroke engine. Won't this type overheat at max. rev if it's only air-cooled? 

Answer: Gaskets are required and are included in the engine kit. Screwdrivers can be purchased at stirringkit.

4. can I ask what type of connectors did you use to attach the glow plugs and starter motor to the battery at once ? What capacity 3s did you use ?

 Answer: This 3-in-1 starter ESC can be purchased directly from stirringkit, taking care of ignition and motor start at the same time. The battery is a 3s lithium battery

5. What's the red fluid in the assembly process and what type of grease for the cam and valves at the top

 Answer: The red liquid is lubricating oil, and the blue one is grease, both of which can be purchased at model hobby shops.

6. One common problem with almost all tiny engine kits, regardless of who makes them, is that their rotating mass is way too small. Replacing the stock flywheel with one that is 2 to 3x heavier makes a world of difference in low RPM operation and general stability.

Answer: Different engines have different applicable scenarios. Some engines follow the simulation route, so it is more suitable for appreciation as a desktop handicraft; but some engines follow the performance route, which is more suitable as a power source for the model.

7. Did I see a different head gasket vs the aluminum used on the l200?.

Answer: We made some changes. The head gasket has been changed because the original water cooling structure has been abandoned.

8. To be clear, this was 7500-8000 RPM. For every full revolution of the 4T engine, the crankshaft rotates 720 degrees. That's why tachometer reading is taken from either the camshaft or distributor, not from crankshaft.

Answer: You are very correct, a complete stroke of a 4 stroke engine is 720°, so the tachometer reading should be divided by 2

9. so does this have a timed spark or does a glow plug just glow all the time and it just timed by the intake cam?

Answer: When you turn on the ESC, the glow plug will be heated until you turn it off

10. How's the crankshaft lubrication done in this FS-L200AC engine ?

Answer: Splash lubrication. Just add the lubricating grease commonly used in the model when assembling

11. What powered screwdriver and torque wrench screwdriver do you use?

Answer:You can find all the essential tools for every engine builder here.
12. Is there something like a diesel RC engine? If so would be cool to buy one and run it on something like oil. If not try to make one? You should have the mashinery to make a RC engine.Just an idea

Answer:The diesel engine is in our plans and is expected to be launched by the end of this year.

13. can you put an airplane propeller in it? the rotation speed is perfect, how is it cooled?

Answer:Natural air cooling. As long as it is not running at high speed all the time, its temperature is within a controllable range. After all, air cooling is more better.

14. Why has the idler pully got so much more contact area with the cam belt than the cam shaft pully?

Answer:What pully contact is not with the toothed side of the belt, which reduces the chance of idler pulley slipping

15. Is anyone else concerned about how little support that camshaft has?

Answer:We've tested it and it's good enough.

16. On every single one of these mini engines I see assembled. The builder just slaps the grease over top of the rockers where it is useless instead of in and around the moving parts. 

Answer:As it spins, the grease is carried where it should by the crankshaft or camshaft.

17. What are the ports on the side? Water cooled? Website says air-cooled

Answer:Air cooling. On the side is the port for taking out waste oil.

18. Why u use glow plugs instead of spark plugs?

Answer:The debugging of methanol fuel is simpler than that of gasoline engine

19.  If it's strong metal, something hardened then annealed back to a softer state, it should work just fine. I mean, by the same metric... think how hard F1 rods last. Those are so small and light yet they can sing God Save the Queen on those engines...

Answer:In order to improve or eliminate various structural defects and residual stress caused by steel casting, forging, rolling and welding, and prevent deformation and cracking of workpieces, all materials are annealed and carefully developed. We strive to use superior materials but control lower costs, so we can do more, you know

20. Plus I'm sure it might also be made with lower friction materials since these don't have oil pumps like the more detailed engines

Answer:This engine model does not have an oil pump, but uses a 2-in-1 carburetor. We have made it as cheap as possible in a number of ways, so that it can meet the budget of all players and enthusiasts.

21. i‘m wondering how the rods survive at those RPM, then again its the weight, just like in a car engine its balanced.and this is super light weight so.. not as much stress?

Answer:As long as the load is not too large and too heavy, the rotation will not have a large torque that will damage the connecting rod. The pressure will not be great under high speed operation .

22. how do the volt regulators work? How much volt do they need to actually have 1.5V at the output for the glow plugs?

answer: you can buy the ignition modules from Stirlingkit. You need to bring your own 7.4V lithium battery. Use it with our ignition module to provide stable voltage to the glow plug.

23. I'm curious, my timing skipped and worried that the valves ran into the pistons. anyone have a thought on that. Otherwise waiting for new starter belts for mine.


Re-adjust the timing system and align the marking point on the crankshaft to the corresponding position.

24. I’m struggling to get the Semto engine started at all. Tried with the glow plugs, no success. Now trying woth gas but still, it won’t start. The spark plugs work well and the hall sensir is accurately placed. It just won’t start. Any videos on this would be useful.


It is recommended to use methanol first. Methanol is easier to debug than gasoline. First check whether the glow plug is glowing. After checking it is normal, install the glow plug to the engine. At this time, start the engine and press the carburetor air outlet once or twice with your hand to suck in the oil. If it still doesn't start, re-adjust the carburetor. Turn the main oil needle to the bottom and then turn it back two turns. Turn the auxiliary oil needle to the bottom and turn it back one and a half turns. After the adjustment, it will run normally.

25. I purchased the Otto 2 cyl motor awsome build I love it great product for the money and a blast to build. However I’m lookn for a starter drive belt or to can not find anywhere any help would be greatly appreciated Ty again great product !!!

you can buy the start belt from Stirlingkit

26. I see some people using torque wrenches. Is there a recommended torque for construction of my semto 2 cylinder? 

Torque specification reference (unit NM):



M2 0.333
M2.5 0.73
M3 1.38
M3.5 2.15
M4 3.12

27. Hey could you also send me a single gear clutch kit for it. I saw you have them on your website and I'd like to try to put this in an RC car. Not sure if I'm going to be able to but I'll need that clutch kit to try. Thanks!

answer: There are three types of clutches: pulleys, gears, and sprockets. It is recommended to use gears.




  • Johannes Golob: July 27, 2023

    how do the volt regulators work? How much volt do they need to actually have 1.5V at the output for the glowplugs?

  • Daniel : April 23, 2023

    I’m struggling to get the engine started at all. Tried with the glow plugs, no success. Now trying woth gas but still, it won’t start. The spark plugs work well and the hall sensir is accurately placed. It just won’t start. Any videos on this would be useful.

  • Robert: March 17, 2023

    I purchased the Otto 2 cyl motor awsome build I love it great product for the money and a blast to build. However I’m lookn for a starter drive belt or to can not find anywhere any help would be greatly appreciated Ty again great product !!!

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