Second hand 2-Stroke Petrol Engine Sachs 4.2 / Sachs-Dolmar 4.2 Large-Scale R/C Petrol Engine – MAHLE Cylinder

Sachs 4.2 / Sachs-Dolmar 4.2 Large-Scale R/C Petrol Engine – MAHLE Cylinder

Vintage German Sachs/Dolmar 4.2 cu in two-stroke petrol engine adapted for large-scale radio-control aircraft. The engine is fitted with a genuine MAHLE cylinder assembly and Tillotson-style diaphragm carburettor, with the characteristic Sachs/Dolmar construction and heavy-duty crankcase.

The Sachs 4.2 is approximately 69 cc in displacement and is a single-cylinder, air-cooled two-stroke petrol engine originally developed from the Sachs/Dolmar chainsaw power unit. These engines became popular in large-scale R/C modelling because of their substantial torque, robust construction and ability to swing large-diameter propellers.

The MAHLE marking visible on the cylinder is significant. MAHLE has a long-established reputation as a German manufacturer of pistons and engine components, with its engineering history dating back to the early 1920s. The Sachs/Dolmar engines used MAHLE cylinder and piston components.

Sachs 4.2 engines were particularly associated with large-scale aerobatic and scale aircraft during the late 1980s and 1990s. Contemporary R/C competition and modelling literature records Sachs 4.2 engines powering aircraft such as the Ultimate, Extra and large-scale warbirds. Propeller sizes around 21×12 and 22×12 were used in documented applications, although the appropriate propeller depends on the particular engine configuration and setup.

This is a substantial vintage model-aircraft engine intended for large-scale models rather than conventional sport models. The engine incorporates a large finned aluminium cylinder, Tillotson-style carburettor, petrol ignition system, heavy-duty crankshaft and large propeller driver.

Condition: Used vintage engine showing age-related cosmetic wear, oxidation and staining consistent with its age and previous use. The engine turns over freely. It has not been tested by me running, so no guarantee of starting or running performance is made. The ignition wiring is present but has loose wire ends and should be checked before use. The carburettor and fuel system would also benefit from inspection/service before attempting to run the engine.

A particularly interesting engine for collectors of vintage large-scale R/C equipment, Sachs/Dolmar engines and early petrol model-aircraft powerplants.

Technical details

One useful point for your listing: don't describe it simply as a “Mahle engine.” MAHLE is the component manufacturer visible on the cylinder; the complete engine is best described as a Sachs/Dolmar 4.2. MAHLE's own history confirms its long-standing role as an engine-component and piston manufacturer.

The Sachs 4.2 was a serious large-scale R/C powerplant. Contemporary sources show it being used successfully in aircraft weighing roughly 30 lb and above, including large P-51s, P-47s and aerobatic models.

Manufacturer / origin Sachs / Sachs-Dolmar, Germany
Engine type Single-cylinder, air-cooled 2-stroke petrol
Displacement Approx. 4.2 cu in / 69 cc
Cylinder MAHLE
Carburettor Tillotson-style diaphragm carburettor
Ignition Petrol ignition system
Propeller Approximately 21×12 to 22×12 commonly documented
Application Large-scale R/C aircraft
Era Primarily late 1980s–1990s R/C use
Condition Used/vintage; turns over freely; running untested