At a first glance, the Yamaha Seca 400′s spec sheet reads similar to the GS450 spec sheet: an air-cooled, 2-valve, double overhead cam, 180 degree parallel twin with 34mm Mikuni CV carbs, gear primary, counterbalance shaft, transistor ignition, braking form 30 mph in 32 feet, 14.1 second standing quarter at 92 mph, and a 100 mph maximum speed.
Prime differences were the monoshock rear suspension, box-section spine frame, manual cam chain adjustment, cast wheels, separate jack shaft for the alternator, self-canceling turn signals – and the Seca’s party-piece, Yamaha Induction Control System, designed to boost swirl for a better combustion to intensify power at low revs.
However, when compared to the GS450, the Seca did things in a much different way. To compensate for its relative shortage of cubes the Seca’s torque output peaked at 8000rpm and power peaked at the bike’s 10000rpm redline. Despite the YICS, — we rarely let the Seca’s engine speed drop below 5000rpm, because there’s nothing there,- Cycle World said. Yet they liked the Seca’s long fuel range and 60 mpg-plus economy, its comfortable seat and riding position, and found the suspension to be -as good as – maybe better than – anything else in its class.- In terms of handling, -The Seca changes direction easily and is easy to ride quickly,– the Seca is a serious, competent motorcycle worth of any rider’s attention.-
1982-’83 Yamaha XS400RJ Seca
Price then/now: $1999/ $800-1600
34hp @ 10000rpm/100mph
399cc air-cooled DOHC parallel twin
372 lbs. (dry)/55-65 mpg
Wear a cool custom painted full face helmet to match the old school Yamaha XS400RJ Seca, or wear a sturdy carbon fiber helmet.
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