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►Promises, promises. Last
year three of the Big Four manufacturers unveiled the world's first production
turbocharged motorcycles, heralding the dawning of a new age in two-wheeled
travel. It sounded too good to be true; sure enough, it was. Turbochargers on
the boost gave middle-displacement machines wondrous power, yet the trade-offs
resulted in a net loss. Two shortcomings—limp-wristed power off the boost and
annoying turbo lag—handicapped the first-generation turbos. Though these
machines showed promise, they weren't functionally superior to 1100cc
Superbikes. The turbo bikes were successful despite their turbocharged engines,
not because of them. How green these first-year efforts were has become apparent
in their second year of production. Honda's 1983 CX-Turbo is vastly improved,
enough that some riders will consider the 650 Turbo a viable alternative to a
normally aspirated 1100cc sport bike.
Many of the 500TC's shortcomings arose from its modest
displacement; off the boost it felt somewhere between a normally aspirated 250
and 400. Honda has logically increased the displacement of the CX-Turbo, and as
a 650 the CX-T has considerably greater off-boost power than the old 500 or the
Yamaha and Suzuki 650 Turbos. Consequently, the Honda is a pussycat in town.
Once the engine hits the boost, however, the CX turns into an absolute animal
with stunning mid-range punch. In roll-on contests from 60 mph against the
Superbike King, the Suzuki GS1100, the Honda easily jets away. That, friends,
makes the CX650T the all-time roll-on champ.
Like the
other 1983 CX/GL V-twins, the 650 Turbo displaces 674cc on an 82.5 x 63.0mm bore
and stroke. Honda engineers also bumped the Turbo's compression ratio, further
increasing off-the-boost power. The CX500 Turbo made do with 7.2:1 pressure, the
650 Turbo runs 7.8:1, and, for comparison, the normally aspirated GL650 has a
9.8:1 compression ratio.
The CX650T's
valves are larger in diameter than the 500's: 32mm intake and 28mm exhaust
compared to the 500's 31mm and 24mm poppets. As before, the CX uses four-valve
heads and pushrod-actuated valves, but the 650's intake valves have greater lift
than the 500's, and the 650 intake ports and injector bores are further
enlarged. Airbox volume is also up.
To feed the
larger engine, Honda enlarged the IHI turbocharger: the 650's compressor wheel
is 51mm in diameter, up three millimeters from the 500's, while the exhaust
turbine remains 50mm in diameter. The 650's waste gate begins to open at 16.4
psi of boost, down one psi from the 500. Nevertheless, the Honda has
impressively high boost pressure.
Last year's
CX-T had a dazzling array of fail-safe backup elements built into its turbo and
fuel injection systems. This year the factory engineers simplified and
rationalized the 650's control systems. They incorporated the ignition-curve
control system into the main fuel injection computer, and dropped a number of
safeguard components, including an air pressure sensor, an ignition sensor and
the resonance-damping "Helmholtz" chamber. The fuel-injection computer has
picked up the extra tasks with little detriment to engine operation.
One notable
exception is starting. Although last year's Turbo started eagerly, hot or cold,
the 1983 version starts reluctantly when cool. Unlike the 500, the 650 has a
choke lever; in reality, this lever opens the throttle butterfly valves a crack
and lets the computer adjust fuel mixture. When the CX is cold the starter
button actuates an enriching circuit. Our 650 required a bit of cranking in the
morning, and it stumbled under low throttle openings until reaching temperature.
Once warm, the CX starts hesitantly at times, but it runs cleanly. Aside from
the low-speed, cold-engine glitch, the Honda meters fuel accurately.
 A
674cc engine and revamped suspension components make the new Turbo a
well-rounded mount. 
Launching
the Honda 650 Turbo from a dead stop is much easier than launching the 500 CX-T.
The 500 rider had to allow for the Turbo's leisurely pickup when turning in
front of oncoming traffic or leaving stop signs. The 650 CX-T has adequate,
though not impressive, power before hitting the boost, and enough off-idle
strength to handle walking-speed parking-lot duty. This improvement in low-end
power complements the new Turbo's taller overall gearing and wider fourth/fifth
jump.
Seriously,
though, nobody buys a Turbo to plonk along at trials-riding speeds. People buy
Turbos for that onthe-boost rush of big horsepower. In this, the Honda surpasses
every other bike on the market. The 1983 Turbo changes make the 650 CX-T much
more rpm-dependent than the old version; as engine speed increases, turbo lag
decreases proportionally. Lag might last as long as two seconds if you hit the
throttle when the engine is lugging way down low, but only a second passes when
the engine is turning around 5000 rpm. At 6000 rpm and above, power arrives
instantly. At all rpms, when power comes on the boost it arrives suddenly,
forcefully and unmistakably. Nothing matches the CX650T for mid-range power.
The Turbo's
savage immediacy is a mixed blessing for serious sport riders. Like last year's
bike, the 650T works best on wide-open backroads filled with broad, sweeping,
high-speed turns, where you have plenty of working room and can see far ahead to
plan cornering strategy; the Honda's huge power surplus is breathtakingly fun,
and reduced turbo lag makes the 650 a joy to ride fast. The CX-T also works well
on moderately tight roads. When the 500 fell off the boost, it simply crawled
out of tight corners. The 650, in contrast, accelerates reasonably well at low
boost pressure, and comes on power much sooner than the 500. On these tighter
roads, though, too much throttle will cause a strong and abrupt shift from
off-boost to on-power that makes the rear end drift out in mid-corner. The Turbo
rider must adapt: When the CX starts to come on the boost he must nick the
throttle back to avoid the sudden power surge, then slowly redial to feed in
power controllably. These demanding power traits divided our staffers: some
worked easily around the Turbo's demands; others never completely adapted to the
CXT's power delivery. Everyone could ride the Honda briskly down backroads, but
some never trusted the CX enough to step up the pace. Even with the improved
engine characteristics, the CXT's turbo-related power will hinder all but the
most talented riders on extremely tight and twisty roads. Though yards ahead of
the 500 Turbo, the CX650T engine remains less flexible than a big normally
aspirated powerplant.
Substantial
improvements to the Turbo's suspension components upgrade the CX's backroad
handling markedly. On the 650T, the TRAC-equipped 37mm air-adjustable fork has a
brace connecting its legs and stiffening the front assembly. Greater rebound
damping (40 percent stiffer than last year) was a much-needed change. Last year
the 500 had a nonadjustable shock; now the Pro-Link rear suspension system
features a shock with three-way adjustable rebound damping. The 650's lightest
setting matches last year's single damping rate—a good compromise setting but
insufficient for hard sport use; the new number two setting stiffens damping 14
percent, the number three setting 29 percent. Honda engineers also increased
shock compression damping a whopping 4.4 times. These combined changes make the
CX-T much more stable and taut-feeling than before.
The 650 CX-T
exhibits no hobby-horsing through fast, bumpy corners—it handles winding roads
with a composure the 500 lacked. With eight psi in the fork, 40 psi in the rear
shock, and the damper set on number four, the CX carves through fast canyon
roads with hardly a bobble. Through 100-mph-plus sweepers, the 650 shimmies just
a wisp—nothing to raise your pulse rate above its backroad level. On knotty
roads, the
Honda can be
cumbersome; at 571 pounds fully gassed, the CX weighs as much as an 1100cc sport
bike, and the CX-T's 58.9-inch wheelbase makes it just a touch shorter. The 650
Turbo feels as if it carries a lot of weight high in the chassis; this, together
with the nature of turbocharged power, can prevent the CX-T rider from feeling
relaxed when the road becomes as tight as scrambled pasta. Only a deft throttle
hand and a good sense of timing will overcome that clumsy feeling and allow a
rider to begin to exploit the 650T's power.
The 650's
triple disc brakes are quite good, though they fade with brutal use. The front
dual-disc offers strong stopping power directly proportional to lever pressure,
and lever pull is solid. Honda's excellent anti-dive fork valving system—we set
the TRAC adjusters on the number four (heaviest) position and left them
there—enhances the Turbo's above-average ground clearance. Eventually, the
exhaust pipe hits on the right side, and the centerstand tang scrapes on the
left.
The new Turbo Honda also serves admirably as a
long-distance mount. Soften up the damping and air-adjustable suspension
components, and the CX delivers a remarkably plush ride—not Gold Wing
caliber, but close. An excellent seating position adds to the Turbo's
freeway comfort, and a new handlebar cures one minor complaint we had
with the 500T Our tallest rider (six-foot) felt a touch cramped on the
650, but other staffers loved the seat/peg/bar relationship. That same
six-footer also disliked the seat shape; the rider's portion of the seat
slopes downward slightly near the mid-seat hump, forcing him forward as
he tried to stretch in the saddle. For everyone else the seating
position was an ergonomic success. The CX-T's swoopy fairing shields the
rider's torso almost completely, and the turn signals protect his hands.
Honda shortened the windscreen about an inch to reduce buffeting—the
face-level air blast is still mildly annoying. Between the lower portion
of the fairing and the jutting cylinders, the Turbo provides plenty of
leg protection. Much warm air from the radiator and engine flows back
onto the rider; it is welcome on chilly days, unwanted on hot.
Honda controlled vibration well. The Turbo transmits a distinctive,
non-objectionable Vee rumble; a light buzz through the handlebars tires
the rider's hands after long stints in the saddle, but that's it. Some
of the credit for the 650's smoothness must go to the Turbo's new
gearing: the 650 turns a leisurely 3876 rpm at 60 mph; the 500T spun a
busy 4496 rpm.► |
Bike Tests 
