CISON FL4-175 Flathead Inline 4 Cylinder Four Stroke 9,000rpm RC Water-cooled Gasoline Engine 17.5cc

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CISON FL4-175 Flathead Inline 4 Cylinder Four Stroke 9,000 rpm RC Water-cooled Gasoline Engine 17.5cc

Shipping update on 2022/10/14:  this engine is in stock now, 6pcs for kit version, and 2pcs finished version. hurry up or it will have no stock. any problems please contact



Miniature Engineering Models that Run on Fuel

This small silver engine, called FL4-175, is a 17.5cc water-cooled flathead side-valved engine that burns gasoline on CDI ignition. A small amount of oil is added to the crankcase for internal lubrication and caster oil is added to the fuel for upper end lubrication. Aluminum CNC precision machining is used to make the main body of the engine. It features bi-metal piston rings made out of cast iron, high-performance hardened cylinder liner, one-piece crankshaft. Sandblasting oxidation on the engine surface makes a good metal texture and sense of mechanical engineering.

As we all know, a flathead engine is also called as a sidevalve engine or valve-in-block engine that is an internal combustion engine with its poppet valves contained within the engine block, instead of in the cylinder head, as in an overhead valve engine. In the past, Sidevalves were widely used internationally by automobile manufactures from the late 1890s until the mid-1950s but were replaced by more efficient overhead valve and overhead camshaft engines. 

To provide an impressive performance, this unique FL4-175 engine features a simple and reliable construction, a compact small size but with large displacement. It's a good combination of retro and modern machinery. 

Long stroke and high torque

the engine is designed with a side valve structure for lower gravity and lighter weight and offers higher torque output based on the long stroke. Having higher torque allows for greater horsepower at lower rpms.

Responsive and powerful

the engine boasts metal stainless steel integrated printing inlet pipes and exhaust pipes and independent single carburetor for easy calibration, more sensitive throttle response, deep and powerful sound.  

Effective and lasting work

the external oil pump is utilized for crankshaft supplement and superior independent lubrication when matched with mini oil filters. The engine is cooled with water cycle for longer operation and lifespan.  

Convenient ignition

the self-developed four-cylinder electronic igniter with a compact size and strong anti-interference makes the engine ignition more stable and more friendly to remote control electronic device users.  


the oil bottom shell is reserved for observation window which is modifiable into a transparent window for real-time crankshaft operation observation. The flywheel end is reserved for the installation of simulated automobile mechanical manual clutch for users to upgrade.  

RC compatibility

the lightweight engine is compatible with RC models and is an incredible "heart" for low torque demanding 1/8 and 1/10 scale model crawlers.


Collection and gift

the engine makes a perfect addition for machine enthusiasts, engine model aficionados and collectors, an excellent choice for RC oil models and a high-end personalized gift for family and friends.


base, CDI igniter, spark plugs, battery and oil filter are not included. buy it here.

i recommend you use the 2S-3S lithium battery (7.4-12V battery). Please use the engine in line with the instructions to avoid damage by improper operation. Please feel free to contact us if you have any questions.  
Buy other accessories here.


.Material: Metal
.Brand: CISON
.Model: FL4-175
.Form: assembly version
.Cylinder Dimensions: 96 x 43mm
.Weight: 1100g
.Displacement: 17.5cc
.Bore: 16.7mm
.Stroke: 20.0mm
.Torque: 1600-9000RPM (or adjusted to lower idle speed)
.Power: 2.5PS
.Lubrication Method: splash lubrication/independent lubrication
.Cooling Method: water cooling
.Ignition Method: self-developed four-cylinder CDI electronic ignition
.Start Method: electric
.Power Supply/Battery: 6-12V / 2-3S lithium battery
.Fuel: gasoline
.Suitable Age: 14+  
.Product Dimensions: 13.5 x 4.3 x 9cm
.Product Weight: 1500g
.Package Dimensions: 20 x 15 x 15cm
.Package Weight: 1700g
.Packing: Graphic Carton

Customer Reviews

Based on 3 reviews
Another GREAT engine from Cison

My FL4-175 came as a kit, I like that wery much ! The parts of this tiny four cylinder 17cc engine looks great, nicely packed in a wooden box. This engine is a flat head with valves on the side in the cylinder block, like most engines before the WWII used in the Willis jeep etc. I want to run mine in a mahogany Gentlemans Racer 1/4 scale, there seems to be a real clutch ( not centrifugal) under developement, this will be great, a reverse would be even nicer!
I'm really looking forward to build this kit, and install it in the kit. (Unless the in line 6 will fit.) Aneyway I really think this is great value for your money if you like small engines. Mine was number 53 out of 100.

Larry B

What a fun project putting this little engine together. Everything is made just like a real automobile engine. I wish the instructions were better but there some videos on Youtube that detail its construction. Enjoy!

Sven Jantzon
Uber exciting!

This little engine is incredible. The workmanship and attention to detail is next level. I have promised myself to wait to assemble so that I can do so with my infant daughter once she is old enough. Will make for great memories and learning experience for a show and tell exhibit. Thank you so much for offering such a great model and project. Very well packaged and the beautiful wooden box is a bonus. Cheers!