Did it work? The Seca 550’s test fuel consumption of 53mpg suggests it did. The idea was to create extra swirl in the combustion chamber and therefore more efficient combustion. Cast into the head was a second, smaller set of intake ports connected across all cylinders, so that each cylinder received two simultaneous charges of fuel/air mixture - one from its own intake port, and one at much higher velocity from the YICS “sub-intake” port positioned just above the valve head. The novel cylinder head design featured Yamaha’s YICS induction control system. Also conventional was the non-adjustable front fork, with dual shocks (adjustable for preload) at the rear. A conventional steel tube frame and swingarm ran on cast alloy wheels fitted with a single front disc brake and rear drum. ![]() And while the 650’s final drive was by shaft, the more sporting 550 used a chain. The jackshaft provided gear drive to the 6-speed transmission, which, unlike the stacked shafts of the 5-speed 650, was laid out horizontally. Unlike the 650, which used gears for primary drive, the Seca 550 crankshaft drove a hydraulically tensioned Hy-Vo chain to a jackshaft carrying the clutch and alternator. More than just a 650 on a diet, the Yamaha XJ550 Seca was essentially all new. The first XJ was the 650, launched in 1980, with the 550 joining it a year later. In continuous production from 1980 to 2008, the air-cooled, eight-valve DOHC inline four has been available around the world in 400, 550, 600, 650, 750 and 900cc form. ![]() If the test of a good design is longevity, the XJ engine line must be considered one of the best. Yamaha XJ550 Seca Claimed power: 50.46hp (rear wheel) 10,000rpm (period test) Top speed: 110mph Engine: 528cc air-cooled DOHC inline four Weight: 424lb (with half-tank fuel) Price then/now: $2,529/$1,300-$2,700
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |