Coming Soon: SEMTO ST-FL2 8.6cc Inline-Twin Engine Kit
The story of the new ST-FL2 begins with another SEMTO twin-cylinder engine familiar to many Stirlingkit builders: the SEMTO ST-NF2. Following the response to the ST-NF2, SEMTO continued developing its next compact twin-cylinder platform.
In 2026, that work brings us the new SEMTO ST-FL2 — an 8.6cc SOHC inline-twin four-stroke nitro engine designed for DIY assembly, running and future RC projects.
With a new design language, water cooling and a compact layout, the ST-FL2 joins the more approachable side of the functional model engine lineup at Stirlingkit.
One of the Best Entry-Level Nitro Engine Kits to Build
The ST-FL2 is designed for hobbyists who want to move beyond static mechanical models and start exploring a real running miniature engine. Like the ST-NF2, it sits on the more approachable side of Stirlingkit's functional engine lineup.
For builders searching for an entry-level nitro engine kit, a model engine for beginners, or a first DIY four-stroke engine project, the ST-FL2 combines hands-on assembly with the experience of starting and tuning a functional miniature internal combustion engine.
What Is the SEMTO ST-FL2?
The SEMTO ST-FL2 is a new 8.6cc DIY inline-twin four-stroke nitro engine kit for 2026. It features an SOHC valvetrain, water cooling and electric starting, and is designed for hands-on engine building, mechanical learning, collection and potential custom RC applications.
Build a Fully Functional Four-Stroke Engine Yourself
The ST-FL2 is a functional miniature internal combustion engine, not simply an electrically driven simulation. Its 8.6cc inline-twin configuration uses two cylinders, a four-stroke combustion cycle and a single overhead camshaft (SOHC).
Building the engine yourself gives you a hands-on look at how the pistons, crankshaft, camshaft and valves work together. Instead of only watching a finished engine run, you assemble the mechanical system that makes that movement possible.
From Parts to a Running Engine
This exploded view provides a simple look at the overall construction of the ST-FL2 before assembly.
How the ST-FL2 Four-Stroke Engine Works
Like a full-size four-stroke internal combustion engine, the ST-FL2 operates through four basic stages: intake, compression, power and exhaust. The SOHC system controls valve timing while combustion moves the pistons and turns the crankshaft.
Intake
The intake valve opens as the piston moves down, drawing the fuel-air mixture into the cylinder.
Compression
The piston moves upward and compresses the mixture inside the cylinder.
Power
Combustion drives the piston downward, producing the mechanical force that turns the crankshaft.
Exhaust
The exhaust valve opens and the piston pushes the combustion gases out of the cylinder.
An Entry-Level Model Engine With Room to Explore
Approachable Starting Point
Positioned among Stirlingkit's more approachable functional engines for hobbyists beginning to explore running model engines.
SOHC Inline-Twin
An 8.6cc twin-cylinder four-stroke engine with a single overhead camshaft layout.
Water-Cooled
An integrated centrifugal water pump forms part of the engine's water-cooling system.
RC Potential
Its compact layout was developed with 1/8-scale RC and custom mechanical projects in mind.
Build → Start → Tune → Explore
Building the engine is only the beginning.
From Model Engine Kit to Custom RC Project
At approximately 113.1 × 91.5 × 103.4 mm and around 0.9 kg, the ST-FL2 uses a compact layout developed with 1/8-scale RC projects in mind.
Actual installation depends on the RC platform, drivetrain, mounting solution and cooling setup. This leaves room for hobbyists who enjoy designing and modifying their own RC builds.
Possible Uses
- Custom RC projects
- Engine test benches
- Mechanical demonstrations
- Custom drivetrain projects
- Desktop engine collections
A Fresh Look for SEMTO
The ST-FL2 combines metal construction with CNC-machined components, sandblasted surfaces and anodized finishes.
Its new green upper cover creates a distinctive appearance while exposed mechanical elements retain the character of a functional miniature engine.
Two Approachable Ways to Start Exploring Model Engines
The ST-FL2 joins the SEMTO ST-NF2 on the more approachable side of the SEMTO functional engine lineup. Both offer builders the experience of assembling and running a miniature twin-cylinder four-stroke engine.
The ST-FL2 brings a different configuration with its SOHC layout, water-cooling system, updated styling and stronger focus on future RC projects.
Explore the SEMTO ST-NF2 →More Ways to Build Around the ST-FL2
Additional accessories and configurations are planned to expand what builders can do with the ST-FL2.
Be the First to Know When the ST-FL2 Is Available
If this new entry-level twin-cylinder engine interests you, select “Notify Me” on the ST-FL2 page so you don't miss its official release.
View ST-FL2 & Notify Me →SEMTO ST-FL2 FAQ
Is the SEMTO ST-FL2 suitable for beginners?
The ST-FL2 is positioned as one of Stirlingkit's more approachable functional model engine kits and may be a suitable starting point for hobbyists who want to learn engine assembly and operation. It is still a real fuel-powered miniature engine, so correct setup, safe operating practices and appropriate supervision are important.
Is the ST-FL2 a real running engine?
Yes. The ST-FL2 is designed as a functional 8.6cc inline-twin four-stroke nitro engine rather than an electrically driven display simulation.
How does the ST-FL2 engine work?
It operates on the four-stroke principle: intake, compression, power and exhaust. Its SOHC system controls valve operation while combustion drives the pistons and crankshaft to produce mechanical power.
Can the ST-FL2 be installed in an RC car?
The engine was developed with 1/8-scale RC applications in mind. Actual compatibility depends on the chassis, drivetrain, mounting, clutch and cooling configuration used in the individual project.
What fuel does the SEMTO ST-FL2 use?
The current ST-FL2 specification calls for 25% nitro fuel.
Looking for More Entry-Level Model Engines?
The ST-FL2 is one of several options for hobbyists beginning their journey into functional miniature engines. Explore Stirlingkit's engine model kits for beginners to compare more approachable projects and find the right place to start.
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