Yamaha YDS7 (1966-67)

The Yamaha YDS7 is a motorcycle produced in 1966-67 with a two-stroke, 247cc parallel twin engine. It has a compression ratio of 7.5:1 and is air-cooled with two Mikuni VM24SC carburetors. The electrical system includes a Mitsubishi 65-watt dc generator, six-volt battery, and coil ignition. The YDS7 has a maximum power of 24 hp at 7500 rpm and a maximum torque of 18.1 ft-lb at 7500 rpm. The clutch is wet and mounted on the left side of the crankshaft, and it has a 5-speed transmission with a top gear engine rpm of around 2500 at 30 mph. The front suspension includes telescopic forks with hydraulic damping, while the rear suspension consists of dual shocks and a pivoted rear fork controlled by spring-and-hydraulic units with three-position load adjustment. The YDS7 has drum brakes both in the front and rear and runs on 3.00-18 front and 3.25-18 rear tires. Its dimensions are 2006mm x 792.5mm x 1066.8mm, with a wheelbase of 1470.5mm and a wet weight of 145kg. Its fuel capacity is 11.4 liters.

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Technical specifications:

Make Model: Yamaha YDS-3C

Year: 1966-67

Engine: Two stroke, piston-port, parallel twin, Crankshaft supported in four roller bearings; needle-roller small-end and big-end bearings. Light-alloy cylinder head;

Capacity: 247 cc / 15.0 cu-in

Bore x Stroke: 56 x 50 mm

Compression Ratio: 7.5;1

Cooling System: Air-cooled

Induction: 2x Mikunis VM24SC with air filter. Direct-operating, coupled air slides.

Ignition: Generator

Starting: Kick

Electrical Equipment:: Mitsubishi 65-watt dc generator charging six-volt battery through automatic voltage regulator. Coil ignition. 6in-diameter headlamp with pre-focus light unit; 35/35-watt main bulb.

Max Power: 24 hp @ 7500 rpm

Max Torque: 18.1 ft-lb 4.2 kgf-m @ 7500 rpm

Clutch: Wet, multi-plate clutch mounted on left side of crankshaft

Transmission: 5 Speed Helical-gear primary drive. Rear chain % x %in with top guard. Engine rpm at 30 mph in top gear, approximately 2,500.

Final Drive: Chain

Gear Ratio: 1st 2.545 2nd 1.533 3rd 1.167 4th 0.950 5th .0773

Front Suspension: Telescopic forks with hydraulic damping.

Rear Suspension: Dual shocks swinging arm, Pivoted rear fork controlled by spring-and-hydraulic units with three-position adjustment for load.

Front Brakes: Drum

Rear Brakes: Drum

Front Tyre: 3.00 -18

Rear Tyre: 3.25 -18

Dimensions: Length 2006 mm / 79 in Width 792.5 mm / 31.2 in Height 1066.8 mm / 42 in

Wheelbase: 1470.5 mm / 51.9 in

Wet Weight: 145 kg / 320 lbs

Fuel Capacity: 11.4 Litres / 3.0 gal