Overview
Żak
Manufactured by Zakłady Wyrobów Metalowych (ZWM), 1960-1963
A cheaper version of the Ryś moped, the Zak was fitted with a 50cc two-stroke SM38 engine.
Żak History
Żak MR2
The design office of Zakłady Metalowe in Wrocław - Zakrzewo developed a simplified version of the Ryś moped. The main goal of the new design was to reduce production costs, and thus the price of the machine. Side covers, headlamp housing and valanced mudguards were abandoned, and a bicycle-type saddle was used. The vehicle was equipped with a new S38 engine, the production of which was launched by Zakłady Metalowe in Nowa Dęba. The designer of this engine was Eng. Wieslaw Wiatrak. The moped was named Żak MR2, and its production began in 1960.
Engine - Type S38, spark ignition, two-stroke, with backwash, rigidly mounted in the frame of the moped. Cylinder diameter 38 mm, piston stroke 44 mm. Number of cylinders l. Engine capacity 0.498 days3. Compression ratio 6.5. Maximum power 1.3 kW (1.8 hp) at 5000 rpm. Maximum torque 2.9 Nm (0.30 kGm) at 3500 rpm. The crankcase housing, cast in light alloy, divided in the vertical plane, was also the housing of the clutch, gearbox and magneto. Ribbed cast light alloy cylinder with cast iron cylinder liner. Ribbed light alloy head. Crankshaft forged, folded, supported on three ball bearings. Forged connecting rod with double-row roller bearings. Piston were of light alloy, with a slightly convex crown, equipped with two sealing rings. Gudgeon pin embedded floating. Piston port timing controlled the gas flow through the edges of the piston. Lubrication of the engine by petroil: oil ratio 20 : l. Air cooled. Fuel supply: horizontal carburetor, type 012, throat diameter 12 mm. Metal mesh air filter with start-up cover. Dry weight of engine with accessories and gearbox 8.5 kg.
Electrical installation - Data as for the MR1. Drive system - Friction clutch, wet, double disc, mounted on the right journal of the crankshaft. Friction discs with cork inserts. Central helical pressure spring. Transmission of drive from the engine to the gearbox via a toothed gear. Gear ratio 4.75 (57/12). Gear box with two ratios. Constantly meshing gears. Ratios in individual gears: Ib-1.68, IIIb-1.00. Shifting gears with a rotary handle, located on the left side of the steering wheel. Rear wheel drive output on the left side of the vehicle.1. Transmission of the drive to the rear wheel with a single-row roller chain with dimensions of 1/2"X4.88. Number of links - 114. Gear ratio 2.68 (35/13). Chain tension adjustment.
Carrying system - Data as for the MR1.
Braking and steering system - Data as in Ryś MR1 moped.
Bodywork - as for the MR1, with the following changes: Shallow mudguards pressed from pressed metal. The front mudguard is attached to the movable part of the fork. A bicycle-type saddle, with a steel skeleton, with a rubber cover, with the possibility of height adjustment. Tool bag attached to the back of the saddle. Side covers made of plastic, covering the junction of the frame tubes. Pedals with rubber overlays, equipped with reflective lenses.
Dimensions - Wheelbase 1234 mm. Length 1860 mm, width 690 mm, height 1040. Fifth wheel rise 800 mm, ground clearance within the wheelbase 140 mm.
Weight - Own vehicle 47 kg. Permissible load 96 kg. Permissible total weight 143 kg. Permissible boot load 5 kg.
Capacities - Data as in the moped Fig. MR2.
Operating data - Top speed 55 km/h. Fuel consumption 2.0 dn3/100 km. The smallest turning circle to the right is 1.94 m, to the left 1.56 m. Air pressure in the tyres: front wheel 0.175 MPa (1.75 kG/cm2), rear wheel 0.225 MPa (2.25 kG/cm2).
Sources:
Polish History Archive
Zabytkowemotocykleirowery Poland
