Slot-controlled, fan-cooled 38 mm (50 ccm) tuned cylinder compatible with Swiss Sachs 50/2 and 502 engines, which were installed in Alpa, Caravelle, Comet, DKW, Eiger, Göricke, Hercules, Prior, Pony Junior, Rico, Rixe, and Walco mopeds.
Chrigi from Gfellers-Zweirad was personally involved in the development of the “Wummer” racing cylinder and tested it extensively. His feedback was directly incorporated into the design. The result is a cylinder that delivers impressive performance, particularly in the mid-range. The focus here is not on peak power, but on smooth, strong power delivery.
The M40x1.5 mm exhaust thread allows for the installation of all standard exhaust systems. Thanks to the stock-style 37x37 mm bolt pattern for the cylinder head, all standard heads can also be mounted here.
The cylinder is camouflaged with the “30 km” lettering.
Notes:
The cylinder is shipped unassembled and without a piston, gasket set, studs, or other components.
The 60x40 mm bolt pattern for the cylinder studs is designed for Swiss engines and is therefore not suitable for German models.
For optimal power output and a precise fit, the cylinder should be used with a 17 mm swiing® tuning carburetor. This should be installed with a short air filter cap, a matching clamp (short), and the corresponding cover plate (long/deep).
You can find all the optional products listed here in the accessories section.
A good, affordable standard replacement part. GPO – GOOD PARTS ONLY.
| Manufacturer | GPO |
| Material | Gray cast iron |
| Displacement | 50 ccm |
| Crankshaft stroke | 42 mm |
| Nominal diameter | 38 mm |
| Ø cylinder neck | 44.8 mm |
| Hole spacing inlet | 32 mm |
| Ø Outlet outside | 40 mm |
| Camouflaged | Yes |
| Number of fixing points | 4 pcs |
| Outlet type | Union nut |
| Sachs | 502 (Saxonette) - AL , AML 50/2 - L CH (0.8 PS) , ML CH (0.8 PS) , MB (2.6 PS) , MLB (2.6 PS) |
Accessories & related products
GPO piston 38 mm | Sachs 50/2, 50/3, 50/4 fan-cooled
Manufacturer: GPO · Nominal diameter: 38 mm · Ø outside piston (A): 37.94 mm · Compression height (C): 27.5 mm · Curvature (D): 3.5 mm · Total piston height (E): 53 mm · Number of piston rings (F): 2 pcs · Piston ring mold: Rectangular ring · Piston ring impact: Flank safety device (FS) · Ø piston pin (B): 12 mm · Piston ring height: 1.7 mm · Thick piston ring: 2 mm · Weight piston kit: 78 g · Alternative version of the Sachs OEM number: 0290 058 025
CHF 33.90
swiing® revival carburetor 17 mm Bing SSB 1/17/69
Manufacturer: swiing® revival parts · Camouflaged: No · Component group Carburetor: Carburetor complete · Material: Aluminum · Carburetor type: SSB · Nominal diameter: 17 mm · Ø fuel hose connection: 6 mm · Mixed oil connection: No · Vacuum connection: No · Choke control: without choke · Nozzle size: 76 · Mounting type: Flange · Hole spacing inlet: 31 mm · Total length: 132 mm · Width: 85 mm · Height: 100 mm · Area of application: Standard · Area of application: Tuning
CHF 126.90
swiing® revival stud bolt set M5x26 inlet (10.9 strength) | Sachs 50/2, 502, 50/3
Manufacturer: swiing® revival parts · Material: Steel · Surface: galvanized (blue) · Thread type: M5x0.8 (standard thread) · Nominal diameter (thread): 5 mm · Total length: 26 mm · Thread length: 7 mm · Thread length: 14 mm · Width across flats: 8 mm · Strength class: 8 · Strength class: 10.9 · Drive: External hexagon
CHF 5.70
swiing® revival exhaust manifold 28 mm chrome | Sachs 50/2, 50/3
Manufacturer: swiing® revival parts · Material: Steel · Surface: chrome-plated · Ø inside: 25.7 mm · Total length: 368 mm · Color: Chrome · Ø outside: 28 mm · Mounting type: Union nut · Ø External connection: 32.25 mm · Sachs OEM no.: P5005
CHF 44.90
GPO 41 mm "Wummer" Cylinder Kit (slot-controlled) | Sachs 502, 50/2 (CH)
Nominal diameter: 41 mm · Manufacturer: GPO · Material: Gray cast iron · Displacement: 55 ccm · Crankshaft stroke: 42 mm · Ø cylinder neck: 44.8 mm · Ø Outlet outside: 40 mm · Ø outlet inside: 30 mm · Inlet window: 18 x 15 mm · Thread inlet: M5x0.8 (standard thread) · Hole spacing inlet: 32 mm · Ø piston pin (B): 12 mm · Outlet type: Union nut · Number of fixing points: 4 pcs · Hole pattern [mm]: 60 x 40 · Decompressor: No · Camouflaged: Yes
CHF 159.90
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GPO piston 38 mm | Sachs 50/2, 50/3, 50/4 fan-cooled
Manufacturer: GPO · Nominal diameter: 38 mm · Ø outside piston (A): 37.94 mm · Compression height (C): 27.5 mm · Curvature (D): 3.5 mm · Total piston height (E): 53 mm · Number of piston rings (F): 2 pcs · Piston ring mold: Rectangular ring · Piston ring impact: Flank safety device (FS) · Ø piston pin (B): 12 mm · Piston ring height: 1.7 mm · Thick piston ring: 2 mm · Weight piston kit: 78 g · Alternative version of the Sachs OEM number: 0290 058 025
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swiing® revival stud bolt set M5x26 inlet (10.9 strength) | Sachs 50/2, 502, 50/3
Manufacturer: swiing® revival parts · Material: Steel · Surface: galvanized (blue) · Thread type: M5x0.8 (standard thread) · Nominal diameter (thread): 5 mm · Total length: 26 mm · Thread length: 7 mm · Thread length: 14 mm · Width across flats: 8 mm · Strength class: 8 · Strength class: 10.9 · Drive: External hexagon
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