For years Yamaha has built bikes with shaft drive: nice, but without
impressive handling. Now the 900 Seca eye-popper: This time Yamaha really got it
How good can a shaft-drive sporting motorcycle be? Judging by Yamaha's new
XJ900 Seca, very good indeed. You sporting purists might take one look at the
drive shaft and immediately dismiss the Seca from consideration. A big mistake:
this Seca is a great sidearm for Captain Canyon Courageous. The 900 Yamaha has a
sporty riding position, a strong, wide power spread, responsive steering,
abundant ground clearance and well-balanced suspension components. Yet the basic
motorcycle is flexible enough for wide-range, all-round duty, thanks to a
tractable engine and hassle-free suspension tunability.
The 900 resembles other Yamaha four-cylinder machines; the engine
configuration and cases are identical to the company's 650, 650 Turbo, and 750
powerplants. As with the smaller XJs, Yamaha engineers have located the 900's
alternator and starter behind the crankshaft. Consequently, the engine can be
narrower than traditional transverse-four designs, which hang the alternator on
one end of the crank. The 900 also uses many drivetrain pieces and deep engine
components common with the smaller XJs, a strategy further reducing design,
development and production costs. The 900 shares most of its drivetrain pieces
with the Turbo 650, standard strengthened components upgraded for turbo use. The
big bike's transmission is identical to the Turbo unit, except for the secondary
reduction pairing: the Seca 900's is slightly taller (49/36) than the 650/750's
(48/37). As a result, the 900 turns 4222 rpm at 60 mph, about 300 rpm slower
than the smaller-displacement XJs. The 900's transmission shafts stagger in the
vertical plane for shortened engine length, and its clutch is identical to the
Turbo's strengthened unit. Final drive ratios are also identical, even though a
new final-drive housing alters the big XJ's appearance. Furthermore, the 900 has
a magnesium oil pan, lighter and slightly larger than the aluminum pans on the
From the base gasket up, the 900 is new. Yamaha's new low-pressure casting
technique for the cylinder block minimizes the number of air pockets and
improves quality control and heat transfer. The Seca's bore and stroke of 67.0 x
60.5mm give an actual displacement of 853cc. (The 750 measures 65.0 x 56.6mm for
a displacement of 748cc, and the 650, 63.0 x 52.4mm for 653cc). The longer
stroke puts crankcase space at a premium; the 900's rod bolts go in upside down
to conserve crankshaft-to-case clearance.
In the cylinder head a single roller chain drives the double overhead
camshafts. The combustion chambers have two valves each: 36mm intakes and 30mm
exhausts. (The 650/750 inhales through 33mm poppets and exhales through 28mm
pieces.) The 900's camshafts spin directly in the aluminum head and ride in four
journals (not three as per 650/750 practice).
The 900 head also incorporates the Yamaha Induction Control System (YICS).
The YICS head uses a series of interconnected sub-intake ports to swirl the
incoming air/fuel mixture within the combustion chamber, thereby promoting fuel
economy through improved burning efficiency.
Like the 650 Turbo, the 900 has four Mikuni constant-vacuum carburetors.
These 35mm Mikunis work exceptionally well; cold-starting is instantaneous, the
Seca runs willingly when only half-warm, and once up to full operating
temperatures the XJ meters fuel without a hitch. A tiny, almost undetectable bit
of CV lag shows itself at very small throttle openings.
Yamaha arranged the XJ's power-band ideally for a 900-class bike. The Seca,
though lacking the lightning punch of an 1100cc
sport bike, feels much stronger mid-range than 750-class machines. Informal
roll-on comparisons with a Honda Interceptor, an exceptionally torquey 750,
revealed a Yamaha superiority at low engine speeds. In mid-range roll-on
contests, the bikes run dead even, but when the Interceptor finally gets into
the upper portion of its powerband, it leaves the Seca behind.
The 900's drag-strip performance mirrors these findings. With a best run of
11.82 seconds at 113.78 mph, the Yamaha is strong without being breathtaking,
roughly in league with this year's premium 750 sport bikes. Though the 900
buzzes a bit as the engine nears redline speeds, for the most part the Seca runs
smoothly. The five-speed gearbox matches well the Yamaha's broad power, and
shift and clutch action are good. More important, the Seca has precious little
driveline lash, and the nearly dead-nuts-perfect carburetion conceals most of
that. The power train engineers did something equally impressive with the old
up-and-down torque-reaction bop-and-bob of shaft-drive motorcycles: they got a
When designing shaft-equipped motorcycles, manufacturers face a difficult
choice: Either make the rear suspension stiff to control the inherent
shaft-induced rise and fall, or sacrifice rear-end control for comfort's sake.
Most engineering departments compromise, but where others have aimed and missed,
Yamaha hit dead-on.
The all-new suspension components at both ends were designed specifically for
the 900. The twin-shock rear suspension system features five-position spring
preload adjusters and 12-way-adjustable rebound damping. True, Yamaha's off-road
machines have long had multiple damping settings, but the Seca's impressive
range of damping adjustability raises the standard for street bikes.
Even a wide range of adjustability can offer useless suspension options if
the settings are grouped on the borders of the ideal window. With the Yamaha's
shock springs set on the softest preload position and the dampers turned to the
soft side of the standard sixth position, the XJ900 has a comfortable,
responsive ride. Compared to the interstate-only touring rigs, the Seca is a bit
firm, but all our testers agree—the Seca is fine for day-long or even week-long
journeys. Up front, a crossover tube connects the two legs of the air-adjustable
fork. Yamaha recommends a range from zero to 17.1 psi, with 5.7 psi as the
For fast sport riding we set the fork to maximum pressure, jacked the shock
springs to the fourth-highest setting, and turned the damping adjuster three
clicks stiffer than standard. This setup produces a stiff ride, but faultless
suspension action; the Seca never wallows, wobbles or pogos through fast
sweeping corners or bumpy, nasty hairpins. The stiff rear suspension settings
control the shaft's torque reaction well. The XJ900's rear end kicks up mildly
during slam-bang upshifts, and the bike never loses significant ground clearance
unless the rider slams the throttle shut halfway through a corner. Since the
Seca has such generous ground clearance, anyone who scrapes the undercarriage
would presumably be skilled enough to compensate for this mild drive-shaft
The Seca's pegs touch down before anything else grinds, and expert riders
eventually touch the centerstand and sidestand tangs on the left of the bike.
The rear Bridgestone tire provides plenty of traction; as you press the front
toward the outer limits of traction, however, it squirms and wanders a bit,
diminishing cornering confidence. The Mag Mopus-L303 has long been a standard
front tire on Japanese bikes, but as OEM rubber improves, the 303 grows more
Like the new suspension components, the Seca's steering geometry and
wheelbase dimensions are unique to the 900; at 58.3 inches the 900 measures 1.3
inches longer than the 650 Turbo and 750. This increase, as well as a wider
front rim and tire, would make the big Seca steer more slowly were it not for
altered steering geometry. The 900 has 27.0 degrees of rake with 4.5 inches of
trail (the 650T and 750 measure 28 degrees and 4.5 inches). Consequently, the
900 feels like a nimble 750 rather than a big one-liter. The 900 weighs a modest
534 pounds fully gassed, and in physical dimensions could easily pass for a 750.
By seat-of-the-pants feel, the big XJ, with its fairly quick and light steering,
falls between the quick-responding Honda Interceptor and the slower-steering
The Seca 900 also rates highly in the brake department. Yamaha outfitted the
XJ with three new-generation disc brakes - ventilated rotors and dual-piston
calipers. The rear brake has progressive action with good feel; it's not overly
sensitive. The front dual-disc setup is simply excellent, ranking with the best
street bike brakes available today. The brakes feel firm and positive through
the lever, provide strong and linear stopping power, yet require only modest
lever pressure. Though linked to the front brakes, the hydraulic anti-dive
doesn't hurt brake performance in the least. Wink-adjustable, this system lacks
sufficient resistance for our testers even on its full-resist position. More
range, please. Get those rear suspension guys working on anti-dive!
All riders should applaud the Seca's excellent seating position. The 900
places the pilot in a light forward crouch; the flattish bars sweep backWard a
bit, and the pegs sit directly beneath the rider's torso, exactly where we think
they should. This seating position works splendidly under all conditions; the
rider sits poised, ready for active riding, yet he is well-balanced against the
oncoming windblast. Our range of testers, from five-eight to six-one, judged the
900's seating position as nearly perfect as anyone is likely to build into a
mass-produced motorcycle. Our shortest testers would have liked the bars better
moved back a touch; our tallest rider would have preferred to move the bars
forward just a pinch. In both cases, the riders were picking nits. Incidentally,
the two-way adjustable handlebars have very coarse adjusting splines that permit
only gross changes in bar position. Finer splines would expand the adjustment
range, further improving ergonomics.
The small quarter-fairing deflects windblast well, completely protecting the
rider's torso. Shorter riders may find the windscreen ducting air at their chins
and directing some turbulence into their helmets. Our smaller staffers moved
back on the seat or sat more upright for temporary relief. Here's more reason
for a finely adjustable bar.
The 900 holds a healthy 5.8 gallons of fuel, giving the XJ a long-legged
range of 255 miles at our average fuel consumption rate of 44.0 mpg. One
mild-mannered freeway cruise netted 56.7 mpg; restrained riders will cover 300
miles with a full tank.
Long-term, steady-state cruising reveals a light buzz in the bars, becoming
mildly irritating after a couple of hours. The mirrors, with very short stalks,
force the rider to work for a view rearward, and after a while, most people tire
of seeing their arms. Day-trippers will like the storage area found in the tail
section, the digital clock, and the best self-cancelling turn signals in the
business. Most important is the go-forth-and-forget-it shaft drive.
And that's the heart of the matter— the Seca 900's real attraction is its
never-think-about-it nature. Plenty of high-performance sport bikes just glut
the market; shaft-equipped Specials, standards and touring rigs abound, too. But
precious few shaft-drive bikes earn genuine sport bike status. With the Yamaha
XJ900 Seca, you get the sport and the shaft, and will be delighted with both.