Yamaha YDS-7 (1972) vs Yamaha RD 250 (1972) vs Yamaha SR 250 (1978-79)
Comparison technical specifications
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| Make: | Yamaha | Yamaha | Yamaha |
| Model: | YDS-7 | RD 250 | SR 250 |
| Years: | 1972 | 1972 | 1978-79 |
| Engine: | Two stroke, piston-port, parallel twin | Two stroke, torque induction, parallel twin | Four stroke, single cylinder, SOHC, 2 valve |
| Capacity: | 247 cc / 15.0 cu-in | 247 cc / 15.0 cu-in | 239 cc / 15.2 cu-in |
| Bore x Stroke: | 54 x 54 mm | 54 х 54 mm | 73.5 x 56.5 mm |
| Compression Ratio: | 7.5;1 | 6.7:1 | 8.9:1 |
| Cooling System: | Air-cooled | Air cooled | Air cooled |
| Induction: | 26mm Mikuni | 2x Mikuni VM28 SC carburetor | 34mm Mikuni carburettor |
| Ignition: | Mitsubishi contact breaker | Battery and coil with breaker points | Electronically |
| Starting: | Kick | Kick | Electric |
| Max Power: | 30 hp @7500 rpm | 30 hp / 22.3 kW @ 7500 rpm | 21 hp / 15.7 kW @ 7700 rpm |
| Max Torque: | 21 ftlb @ 7000 rpm | 21 lb-ft / 2.9 kgf-m @ 7000 rpm | 18.7 ft-lb / T25.5 Nm @ 7000 rpm |
| 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. | 6 Speed | 5 Speed |
| Final Drive: | Chain | Chain | Chain |
| Front Suspension: | 34mm Telescopic forks | Telescopic forks | 32mm Telescopic forks |
| Rear Suspension: | Twin shock | Dual shocks | Dual shock 5-way preload adjustment. |
| Front Brakes: | 180mm twin leading shoe drum | Drum | Drum |
| Rear Brakes: | 180mm single leading shoe | Drum | Drum |
| Front Tyre: | 300 x 18 | 3.00S-18-4PR | 3.00-18 |
| Rear Tyre: | 3.25 x 18 | 3.50S-18-4PR | 120/90-16 |
| Wheelbase: | 1300 mm / 51.1 in | 1325 mm / 52.1 in | 1340 mm / 52.75 in |
| Fuel Capacity: | 11.4 Litres / 3.0 gal | 16.5 Liters / 4.2 US gal | 10.8 Litres / 2.7 US gal |