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1982-83 Yamaha XJ650 Lj/Lk Seca Turbo |
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| Suggested price in 1982 | $4,999 |
| Suggested price in 1983 | $3,500 |
| ENGINE | |
| Type | Air-cooled transverse turbocharged four-stroke in-line four |
| Valve arrangement | DOHC, 2 valves per cylinder, adjusting shims on top of buckets |
| Carburetion | Four 30mm pressurized Mikuni CVs |
| Displacement | 653cc |
| DRIVE TRAIN | |
| Clutch | Wet, multi-plate, 5-speed |
| Final Drive | Shaft. 4.179:1 |
| CHASSIS | |
| Front suspension | 36mm Showa ('83: 37mm), 5.5 in. travel, adjustments for air pressure |
| Rear suspension | Dual Showa dampers, 3.1 in wheel travel, adjustments for air pressure, rebound damping |
| Front tire | 3.25 V19 Bridgestone Mag. Mopus L3030 |
| Rear tire | 120/90 V18, Bridgestone Mag. Mopus G508 |
| Wet weight | 565 lbs. (257 kg) |
| Fuel capacity | 4.2 gal. (15.75 L), '83: 5.2 gal. (19.5 L) |
| PERFORMANCE | |
| Average touring range | 198 miles ('83: 246 miles) |
| Best 1/4 mile acceleration | 12.68 sec., 106.13 mph ( Cycle World , June 1982) 12.06 sec. 109.89 mph with wastegate deactivated ( Cycle World , July 1983) |
| 200 yd. top-gear accel. from 50 mph | 74.5 mph terminal speed |
| Total production | '82: approx 6500, '83: approx 1500 |
| Total imported into U.S. | ? |
Best press quote:
"The Turbo Seca transforms itself from motorcycle
to superbike and back again with ease, and the transformation
is simply controlled by the right wrist."
Cycle World, June 1981
Hot on the heels of Honda's CX500 Turbo, the Yamaha 650 Seca Turbo, despite its futuristic looks, was something totally different. With air instead of water cooling, four instead of two cylinders, and, interestingly of all, pressurized carbs in place of fuel injection, the blown Seca took an entirely different approach to what a turbocharged motorcycle should be.
Many expressed doubts as to the durability of an air-cooled engine under duress of a turbocharger; those reservations would prove unfounded (80,000+ mile Seca Turbos that have never had major engine work or even blown a turbocharger are quite common). The pressurized carbs worked very well ("Best carbureted bike I've ever ridden" -- Bob Miller, President, T.M.I.O.A.).
Where the Seca T failed was in the chassis department. Unlike the other factory Turbos Yamaha simply used a stock XJ650 frame for the LJ -- big mistake. A little more effort in this area could have made a world of difference in handling.
'82 Seca Turbos suffered from weak performance when they were initially introduced. Tired of being embarrassed by Honda CX500 Turbos in head-to-head tests Yamaha rushed out a "Power-Up" kit (free of charge!) that consisted of a stronger turbocharger wastegate spring and a washer that you stuck at the end of your right-side muffler to increase back pressure. Both measures were designed to increase boost pressure and keep it in the cylinders longer. Peak boost went from an anemic 7 psi to a respectable 12 psi. The bad news for '82 Seca Turbo owners ('83 models came with the modification) is that Yamaha ran out of the kits in 1985. The good news is that you don't need it. Simply disconnect the vacuum hose leading to the wastegate actuator, clamp it shut, close up the hole in the actuator and experience the thrill of 14 psi. The poppet valve in the surge tank now serves as your "wastegate" to keep the engine from exploding. This also solves the problem of turbocharger wastegates failing to close, a common cause of power loss in Yamaha Turbos (blame it on the placement of the unit under the engine where it collects all sorts of road debris).
Thicker forks in 1983 helped things somewhat but a price drop of $1,400 (or more) help clear the floors of unwanted Seca Turbos. Well kept, low mileage bikes bring about $1,500 to $2,500 today. Showroom examples may fetch $3,000 or more, but Seca Turbos in such a state are extremely rare. '83 models, with their 1mm thicker forks and 1 gallon larger gas tank, are more desirable.
Last Modified March 06, 2007, 18:41:38 Eastern Standard Time
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