S51 / S51 Enduro [M531, M541, M542] Parts

Simson S51 / S51 Enduro - Technical data and information

The Simson S51, produced from 1980 to 1989 by VEB Fahrzeug- und Jagdwaffenwerk “Ernst Thälmann” in Suhl (GDR), is one of the most iconic and durable mopeds of all time. With over 1.2 million units produced, this model was a complete redesign compared to earlier versions. It featured a compact 3.7 hp air-cooled engine that was 10% more fuel efficient, met strict ECE emissions requirements and had an innovative multi-plate oil-bath clutch that was exceptionally reliable even in the toughest conditions.

The S51 range included many variants, from the basic S51 N without battery for use in the countryside to the premium S51 C (Comfort) with adjustable shock absorbers and refined design details. The most iconic variant, however, is the S51 Enduro, which was specially developed for off-road use with a high-mount exhaust, shortened mudguards, reinforced suspension with 130 mm travel at the front and 90 mm at the rear, an enduro-style handlebar and tires with better grip. Considered by many fans as "the best moped in the world", the S51 stands out for its legendary robustness, easy maintenance, a huge range of original and aftermarket parts and an extraordinarily active community that is still keeping tens of thousands of examples running even after more than 40 years.

Engine - Simson S51

The S51 is equipped with a single-cylinder two-stroke engine that is air-cooled and delivers 3.7 hp (2.72 kW) at 5,500 rpm. Maximum torque is 5.0 Nm at 4,800 rpm. Power is transmitted via a manual gearbox with three gears on the basic models (N, B1-3) and four gears on the higher versions (B1-4, B2-4, Enduro, Comfort), allowing a top speed of 60 km/h. Fuel consumption is exceptionally low at around 2.5 liters per 100 kilometers.

The two-stroke engines of the S51 run on a fuel-oil mixture at a ratio of 50:1 (50 parts gasoline to 1 part two-stroke oil) to ensure the internal lubrication and the cooling of moving parts. The rotary disc intake system and multi-plate oil-bath clutch contribute to the engine’s exceptional reliability, which can exceed 100,000 km with proper maintenance.

Engine: Air-cooled 2-stroke single cylinder (2T)
Displacement: 49.9 cc
Maximum power: 3.7 hp (2.72 kW) at 5500 rpm
Maximum torque: 5.0 Nm (0.51 kpm) at 4800 rpm
Bore x stroke: 38 mm x 44 mm
Compression ratio: 9.5:1
Cooling: Air
Fuel: Carburetor BVF 16N1-11 / 16N3-4 (from 1986)
Intake: without reed valve
Lubrication: 2-stroke mixture (ratio 1:50)
Starter: Kick starter
Transmission: 3-speed manual gearbox (N, B1-3) or 4-speed manual gearbox (B1-4, B2-4, E, C)
Clutch: Multi-plate clutch (0.4 liter)
Ignition: 6V contact ignition (old models) or 6V/12V electronic ignition (newer models)
Spark plug: Type 260, electrode gap 0.4 mm
Final drive: Roller chain 1/2" x 5.4 mm (110 links)
Top speed: 60 km/h
Average fuel consumption: 2.5 L/100 km

Chassis and components - Simson S51 moped

The chassis of the Simson S51 was designed for maximum robustness and durability, qualities that earned it its legendary reputation. The reinforced steel-tube frame integrates a fuel tank with a capacity of 8.7 liters (including 1 liter reserve), providing a range of about 300 km. The extremely solid construction with generous tolerances and high-quality steel components explains why tens of thousands of units are still operational after more than four decades.

The telescopic fork is equipped with a hydraulic travel limiter (34 cm³ oil per rod) for stability on the road, while on the Enduro models the suspension travel is extended to 130 mm to absorb shocks on uneven terrain. The rear swingarm with hydraulic shocks (90 mm travel on the Enduro version) offers adjustable preload on the C (Comfort) and E (Enduro) models. Drum brakes at the front and rear ensure progressive and reliable braking performance and are extremely easy to maintain thanks to simple adjustment of the brake shoes and brake cables.

Frame: Reinforced tubular steel frame with integrated fuel tank
Front suspension: Telescopic fork with hydraulic limiter (130 mm for Enduro)
Rear suspension: Swingarm with hydraulic shock absorbers (90 mm on Enduro), adjustable on C and E models
Front and rear brakes: Drum brakes with brake cable
Tires: 2.75 x 16" (K30/K35 standard models, K32 Enduro models)
Unladen weight: 75.5 kg (S51 N) / 79.5 kg (B models)
Tank capacity: 8.7 liters (including 1 liter reserve)
Luggage rack load: 10 kg
Towing capacity: 60 kg (maximum speed with trailer 40 km/h)
Minimum turning radius: 3.25 meters
Number of seats: 2 seats
Cockpit: Speedometer up to 60 km/h (100 km/h for Enduro), indicators (models B2-4, C, E)

Customizing and spare parts S51

The Simson S51 is very popular in Europe for tuning and restoration projects. The simple two-stroke engine in combination with the robust chassis and the almost unlimited availability of original, aftermarket and tuning parts allows individual modifications and custom projects ranging from subtle cosmetic improvements to powerful conversions that can double or triple the original power.

There are also many styling parts for customizing and restorations: Seats, sports handlebars in various designs, modern LED lights, tanks in various designs, chrome parts and complete restoration kits with seals and bearings. You can find all this and much more in our online store!