Manual for the KMD 2.5 ccm russian diesel engine

Not directly related to cars, but as I got hands on that vintage diesel engine and I found that the manual is available nowhere. I'll post here pictures of that manual as well as a (AI generated) translation to english.

Most important was for me the break-in procedure and the stock needle settings.

1. Technical Data

Cylinder diameter: 14.5 mm
Piston stroke: 15 mm
Displacement (working volume): 2.48 cm³
Power (hp), at least:
- with a 3.2 mm nozzle: 0.35 hp
- with a 4.0 mm nozzle: 0.39 hp
Speed with an air propeller (Ø160 mm, pitch 200 mm): ~14,000 rpm
Compression ratio: 12–16
Direction of rotation: counterclockwise (viewed from the propeller side)
Engine mass: ~180 g
Fuel mixture (by volume):
- 45 % kerosene
- 31 % ether
- 8 % castor oil
- 16 % MS‑20 oil
Service life (minimum): 5 hours

2. Scope of Delivery

The KMD 2.5 micro-engine is packaged in a box and includes the following components (quantity in parentheses):

KMD 2.5 micro-engine (1)
Open-end wrench (1)
Nozzle inserts:
- 3.0 mm (1)
- 3.4 mm (1)
Screws (M3×22) (4)
Nuts (M3) (4)
Oil- and fuel-resistant rubber tubing (length ~150 mm) (1)
Operating instructions (1)

3. Safety Requirements

The engine must only be attached via the mounting lugs on the crankcase.
Clamping the engine in a vise is not allowed.
Before each start, verify that the engine is securely fastened.
Use only wooden or plastic propellers. Metal propellers are not permitted.
Never stand in the plane of rotation or directly in front of the propeller while the engine is running.
Starting and operating the engine are allowed only outdoors or in a well-ventilated indoor area equipped with supply and exhaust ventilation.

4. Engine Design & Operation Principle

The engine operates on a two-stroke cycle:

Fuel intake
- Fuel enters through fitting 1 and is metered by the adjustable needle 2.
- Air flows in via the intake nozzle 8 and, in the diffuser, atomizes the fuel, creating a combustible air–fuel mixture.
- This mixture, when the channels in the slide valve 7 and carburetor body 9 line up, passes into the crankcase 6.
Crankcase vacuum & transfer
- As the piston 10 moves toward top dead center (TDC), a partial vacuum forms in the crankcase, drawing the mixture inside.
- Moving the piston downward (toward bottom dead center, BDC) closes the intake port, compresses the mixture in the crankcase, and then routes it via the transfer (scavenge) ports into the cylinder space above the piston, pushing out residual exhaust gases and introducing a fresh charge.
Compression & ignition
- As the piston moves upward to TDC, the mixture in the cylinder is compressed and heats to ignition temperature.
- The mixture ignites, pressure rises, and forces the piston downward (power stroke).
Exhaust
- Toward the end of the power stroke, the exhaust port 5 opens, allowing burned gases to exit to the atmosphere.
- The cycle repeats.

5. Preparation for Operation

Remove protective (preservative) grease
- Rinse all external and internal surfaces of the engine with clean gasoline (petrol) to remove any conservation lubricant.
Mount the engine
- Attach the engine securely to the model or a suitable test stand/fixture.
Connect the fuel tank
- Use the provided rubber fuel line to connect the tank to the engine.
- The tank should be placed close to the engine, and both the tank outlet and carburetor inlet should lie at approximately the same height.
Install the propeller
- Attach a suitable wooden or plastic propeller.
Close the carburetor needle
- Turn the carburetor adjustment needle 2 fully clockwise until it gently seats (do not overtighten).
Fill the tank
- Use pre-filtered fuel (kerosene/ether/castor/MS‑20 oil mixture as per the specified proportions).

6. Starting the Engine

Open the needle
- From the fully closed position, unscrew the adjustment needle 2 by about 1.5–2 turns.
Prime with a few drops of fuel
- Drip several drops of fuel into the cylinder through the exhaust port 5 (optional step if extra priming is needed).
Finger-choke the intake
- Cover the intake nozzle 8 with a finger while turning the crankshaft 2–3 revolutions (counterclockwise from the propeller side) to draw fuel into the engine.
Uncover the intake
- Remove your finger from the nozzle and allow air to flow normally.
Attempt to start
- Flip the propeller (or use a starter) to spin the engine.
- If there is no ignition (no sign of fuel igniting), turn the regulator screw 4 by ½–¾ of a turn and try again.
Adjust for minimal stable RPM
- Once running, use the needle 2 and screw 4 to achieve the lowest stable idle or low-speed setting.

7. Break-In (Running-In) Procedure

Initial break-in period
- Let the engine run for a total of 20–30 minutes in short intervals (e.g., 2–3 minutes running, then a cool-down pause).
- Prevent overheating by running the engine slightly “rich” (turn the needle out 2–3 turns more than normal).
- Each time you restart, you may gradually increase RPM, aiming to reach maximum RPM only toward the end of the break-in period.
Cooling pauses
- After every 10 minutes of continuous operation, shut off the engine for at least 10 minutes to cool down.

8. Maintenance

Foreign matter prevention
- Make sure no external objects or dirt can enter the crankcase or other internal cavities of the engine.
Regular checks
- Periodically check the tightness of the screws on the cylinder head, carburetor body, and carburetor jet/nozzle fittings.
Choosing a propeller for racing models
- Recommended propeller diameter: 180–190 mm, pitch: 190–195 mm, especially if installing on a high-performance or racing aircraft model.
Changing the nozzle diameter
- The standard nozzle is 3.2 mm. A larger-diameter nozzle can increase engine power but also raises fuel consumption.
Using additives
- You can increase engine performance by adding certain additives (e.g., nitro compounds) to the fuel.
- Some references mention up to 2 % “ash” components or up to 2 % aminonitrite.
Extended operation & removing deposits
- After many hours of operation or when carbon deposits noticeably reduce power, partially disassemble the engine.
  - Carefully remove the carbon deposits.
  - Rinse all parts with gasoline.
  - Lubricate with MS‑20 oil.
  - Reassemble.
Disassembly & assembly notes
- Refer to the provided exploded diagram for correct teardown/assembly order.
- When reinstalling the cylinder head, ensure the alignment slot in the upper cylinder liner matches the stop screw (which prevents the liner from rotating).
- A small set screw (often secured with epoxy) locks the liner in place.
Piston orientation
- The piston should be oriented so that its slot/notch faces toward the propeller. Avoid dismantling the engine unless necessary.

9. Long-Term Storage

Thoroughly rinse the engine’s internal cavities with gasoline, then dry.
Lightly coat all surfaces with mineral oil (or similar corrosion-preventative oil).
Plug the carburetor intake and exhaust port.
Wrap the engine in paper or cloth.
Store in a dry, enclosed area, away from substances that may cause corrosion.

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