| MODEL | YAMAHA XJ 650 SECA 1981 |
| Year | 1981 |
| Engine Type | Four stroke, transverse four cylinder, DOHC, 2 valves per cylinder |
| Displacement / Capacity | 653 cc / 39.8 cu in |
| Bore X Stroke | 63 x 52.4 mm |
| Compression Ratio | 9.2:1 |
| Cooling System | Air-cooled |
| Max Power | 51.8 kW / 71 hp @ 9400 rpm |
| Max Torque | 57 Nm / 42 lb-ft @ 7500 rpm |
| Ignition | Transistorized |
| Induction | 4x 32 mm Hitachi carburetors |
| Start System | Electric |
| TRANSMISSION SPECS | |
| Lubrication | — |
| Gear Box | 5 Speed |
| Clutch | Wet multiplate, 7 steel / 8 friction plates |
| Final Drive | Shaft |
| CHASSIS SPECS | |
| Frame | Tubular steel dual cradle |
| Front Suspension | 36 mm Kayaba forks, 142 mm / 5.5 in travel |
| Rear Suspension | Twin Kayaba shocks, 93 mm / 3.6 in travel |
| Front Brakes | 2x 268 mm discs, single-piston calipers |
| Rear Brakes | Drum |
| DIMENSION SPECS | |
| Overall Length | — |
| Overall Width | — |
| Overall Height | — |
| Seat Height | 780 mm / 30.7 in |
| Wheelbase | 1445 mm / 56.8 in |
| Ground Clearance | 145 mm / 5.7 in |
| Dry Weight | 206 kg / 465 lbs |
| Wet Weight | — |
| WHEEL SPECS | |
| Front Tyre | 3.25-19 |
| Rear Tyre | 120/90-18 |
| FUEL SYSTEM | |
| Fuel Capacity | 19.5 Litres / 5.1 US gal |
| Fuel Consumption | 48.6 mpg |
| Top Speed | — |
The Seca is the conventional, standard-style version of Yamaha's shaft-driven air-cooled 650 four, with a tall 19 inch front wheel and twin front discs. Period testers praised its comfort, seat and brakes, but found the engine needed revs and felt flat in the mid-range, with the Suzuki Katana and GT rivals sharper. Standing quarter mile was about 12.6 s in the page's figures.
