Tuoyang Toyan FS-S100 four-stroke engine debugging tutorial

Once upon a time, internal combustion engines still dominated the model market. But with the development of technology, electric motors engines gradually replaced them and became the main driving force in modern models. Compared with electric motors, when using internal combustion engine, it can’t operate normally without undergo very tedious debugging because of its relatively poor stability during operation. And it’s also hard to maintain it after use. Most of the model fans will prefer electric one . However, the internal combustion engine has one significant advantage that the electric engine can’t fight against with. That is, it has a long-lasting life. In addition, in recent years, more and more model friends have begun to prefer simulation car models, and even the engine is required to be simulated as much as possible. in this case, the internal combustion engine has begun to come back to life gradually.

As we know, if a new internal combustion engine is to run normally, it has to undergo very complicated debugging first. So in this article, I will share some tips with you for debugging the internal combustion engine,taking the Tuoyang FS-S100 four-stroke engine as an example. Let’s see how it works!

Material preparation

To turn this engine on, first please prepare the above equipment,like fuel, fuel tank, igniter, starter motor ESC, and spark plugs etc..

The Tuoyang FS-S100 four-stroke engine has a maximum displacement of 3.5cc, an actual speed of 2500-13500 rpm, and a maximum power of 0.5 horsepower (11500 rpm).

The fuel i choose this time is 20% nitromethane. Tuoyang officially recommends 20% -25% concentration of nitromethane. You can also choose 25% -30% gasoline as fuel. As for the fuel tank, a common 100ml is acceptable. Please note that The upper intake pipe is connected to the engine exhaust pipe, and the lower fuel pipe is connected to the engine's fuel inlet. During operation, the engine uses a part of the exhaust gas to be re-injected into the fuel tank, so that the pressure of the fuel tank is increased to "press" the fuel into the engine.

Tuoyang FS-S100 four-stroke engine has been equipped with a brushless motor of the inner rotor pn the manufactured date. And then add and install one more 3S brushless ESC. Toyang recommends using 3s 11.1v battery as the starting power.

The throttle is controlled by a steering gear. Since there is no dedicated steering gear mounting frame, the engine is still a self-made rudder frame. Since the stroke of the steering gear is larger than that of the throttle, after the installation finish, the stroke of the steering gear can be controlled by adjusting the volume of the unilateral steering gear of the steering gear to avoid burning the steering gear.

The internal combustion engine is mainly divided into compression ignition type (such as diesel engine) and ignition type (such as gasoline engine) according to the different ignition methods. Tuoyang FS-S100 four-stroke engine is ignitable type, so the spark plugs are naturally indispensable. However, unlike our common automotive spark plugs, the four-stroke spark plugs used in the model have a platinum heating wire inside. Each time the engine ignites the fuel to expand the work through a heating wire, and at the same time stores part of the heat of the work in the heating wire, so that the next stroke continues to ignite the fuel for work. Because the fuel is ignited by the high temperature generated by the heating wire (similar to the car cigarette lighter), this spark plug is also called "hot plug" or "fire head" in the mold circle.

PS: even though four-stroke’s “hot plugs” look similar with that of the two-stroke in appearance , they still have slight differences in the working principle. Therefore, special glow plugs should be used to avoid damage to the engine.

In practice, Tuoyang's FS-S100 four-stroke engine requires the same ignition device as the ordinary two-stroke model engine. The glow plug is first heated through the internal contacts. When the engine is turned on, the igniter can be removed then.

In terms of lubrication, the Tuoyang FS-S100 four-stroke engine is lubricated by the lubricating oil carried in the fuel, and the excess lubricating oil will be discharged through a drain nozzle at the bottom of the engine.

When everything is ready, and can the engine runs normally when the fuel is turned on? Obviously not, we also need to debug the needle and throttle before it’s turn on.

Commissioning before starting

Due to the different combustion effects of each fuel, there will be differences in the specific adjustment. Here we use UOYIC's 20% nitromethane fuel.

In addition, due to the difference in engine structure, the FS-S100 four-stroke engine has one less oil needle compared with the ordinary two-stroke one, so only one oil needle is needed when adjusting.

Tighten the oil needle clockwise before running, and then loosen it two turns counterclockwise. Generally, the oil needle will remain slightly rich, which can prevent the engine from pulling or expanding cylinders due to lean overheating.

Before starting the engine, keep the throttle at about 20-30% and keep the throttle adjustment screw in the factory position.

Then plug in the igniter and run the motor to start the engine.

At the beginning, because there is still some air in the fuel pipe, it takes some time to completely exhaust the air in the fuel pipe before the fuel reaches the cylinder engine to make it start.

If the engine fails to start, please check if the igniter battery is still charged, whether the glow plug is working properly, whether the fuel reaches the intake nozzle, the throttle size, etc. If everything is normal, if you still can't start the engine, please try to rotate the oil needle of the engine half a counterclockwise, or close the throttle after the starter motor is running to allow more fuel to enter the engine cylinder.


After hearing the engine has a deflagration sound like “pong pong pong”, it means the engine gets started. At this time, turn off the starter motor, unplug the igniter, and warm up the engine (about 20 seconds) to the normal operating temperature. Then you can fine-tune the oil needle and damper of the engine.


Before adjusting the oil needle, first briefly describe what it feels like to use rich oil and lean one one it: running in rich state, the engine will emit a dull sound, its speed will be slightly reduced. and in severe cases, the exhaust port will spray out incompletely burned fuel; under lean conditions, the sound of the engine is relatively crisp and its speed will also increase.

Needle adjustment:

After the engine is running normally, first make a rough adjustment of the oil needle. Adjust the oil needle to keep the engine stable until the throttle is fully open. When the engine is running at high speed, you’d better to keep the engine in a slightly lean state.


Keep the throttle fully open, then immediately lower the throttle to the idle state, and listen carefully to the sound of the engine in the process. If an abnormal noise occurs during the process of lowering the engine throttle, you need to finely adjust the oil needle of the engine to make the engine have enough oil. When the engine emits a relatively stable and consistent sound, the oil needle of the engine is basically adjusted.

Idle speed adjustment:

to adjust the engine's idle speed,  mainly adjust the throttle, which is connected to the engine, and reduce the engine throttle to the minimum, and adjust the screws on the throttle (increasing the idle throttle clockwise and decreasing the idle throttle counterclockwise). The engine idle speed is adjusted until the engine speed is at a minimum and will not stall.

Finally, after running in the two tanks of oil, make fine adjustments according to the running state of the engine to make the engine reach the optimal running state. In addition, due to the different chemical properties of different brands of fuels, the needle needs to be readjusted each time if a different brand of fuel is replaced.

In general, it’s not too difficult to adjust this four-stroke engine because it can run stably after simple adjustment. This is also the most obvious advantage of Tuoyang's FS-S100 four-stroke engine. In terms of noise and smoke pollution, it is much lower than the traditional two-stroke model, especially when the smoke is almost invisible. However, since it is a single-cylinder engine, the vibration is relatively large.