1983 Nighthawk 550
The Little Cruiser with Power!
A great article on the 1983 Honda Nighthawk 550.
1983 CB550SC Nighthawk
Everybody likes power, whether they prefer their handlebars wide and
tall or narrow and low, and some of the biggest skirmishes in the
horsepower war are being fought in the 550 class.
Which introduces the Nighthawk 550, Honda's horsepower entry in the
non low-bar 550 market, a bike with cruiser styling and high
performance.
There's no mistaking the styling-there's chrome everywhere, a short
chrome front fender on long, leading-axle forks; chrome headlight,
carburetor caps, rear shocks, turn signals, instrument covers, and
pullback handlebars; chrome exhaust with rakish, diagonal-cut mufflers.
What isn't chrome is likely to be polished aluminum, like the headlight
mounts, the instrument panel, the grab bar outlining the stepped seat,
the cam cover, the fork sliders, the footpeg bases, the rear footpeg-and-muffler
hangers, the engine covers.
If there's still any doubt, it's displaced by the tiny teardrop gas
tank, the stubby tail section, the cut-back sidecovers and the fat,
16-in. rear wheel.
This is a cruiser. What about performance? Look at the horsepower and
torque figures, 75 bhp at 9500 rpm, 36.5 lb.-ft. at 8000 rpm. Potent
stuff for a 550 Four, and the reasons for that power output lie in the
engine's genealogy.
Air-cooled, DOHC, link-plate cam chain, four valves per cylinder,
offset rocker arms with hydraulic lash adjusters, plain bearing
crankshaft, helical primary gears, hydraulic multi-plate wet clutch,
six-speed transmission, shaft final drive. This is the smaller version
of Honda's newest inline Four, introduced in the Nighthawk 650 and
Nighthawk 550 for 1983. The engines share crankcase castings, clutch,
transmission and cylinder head. The 572cc 550 has lower primary gearing
and the same 60mm bore as the 650; stroke is shorter; 50.6mm to 58mm. To
work with the 50.6mm stroke, the 550 has shorter connecting rods,
crankshaft throws and cylinders. The crankshaft, designed for the 572cc
version, is lighter with 1mm smaller diameter journals; the cases are
machined to fit.
The engine is designed to be compact. It is narrow, the alternator
mounted behind the cylinders, overdriven off the crankshaft by a
link-plate chain. It is short, the transmission shafts staggered
vertically instead of laying one behind the other.
It's also designed for low maintenance. The hydraulic lash adjuster
automatically take up clearance between valve stems and rocker arms -
meaning no valve adjustment is necessary - and pump down if the engine
is over-revved, increasing clearance and reducing the chances of a mis-shift
bending the valves. The transistorized electronic ignition is not
adjustable, and has electronic advance. The hydraulic clutch, like
hydraulic disc brakes, is self-adjusting.
Low maintenance doesn't mean low performance. The 550 has the same
cams as the 650, and, used with the smaller engine, those cams are
closer to the high-performance grinds sold by aftermarket engine
builders than are most stock camshafts. The four Keihin CV carbs have
oval throats, 26.8mm at the venturi, 30mm at the throttle plate, with
lightweight throttle slides and thin diaphragms for instant throttle
response. Combine the cams and the carbs with the lighter crankshaft and
you've got a quick-revving, free-winding 550 that feels faster than
anything in the class.
It feels fast because it has a big jump in horsepower and
acceleration at 7000 rpm, gaining engine speed from there at an
astonishing rate right up to the 10,000 rpm redline. It pulls well from
4000 rpm, well enough to leave lights quickly and have fun gaining
speed, but then there's that kick at 7000 when the Nighthawk comes on
the cams, and off it goes.
There's nothing to distract the rider from that magic rush of the
tach needle toward redline, since the rubber-mounted engine is one of
the smoothest ever put in a motorcycle. That glass-smoothness adds an
eerie quality to the soaring tach and the kick-in-the-pants
acceleration.
Slam the 550 into second gear at redline and the front wheel comes up
and floats a foot or two off the ground, slowly settling as the bike
continues to gain speed. Keep the Nighthawk near the redline, shifting
quickly, and a rider on anything short of a sporting 1100 will have to
work to keep up or pass. Street impressions send a strong message, that
this is the most potent, quickest, fastest 550 around.
A trip to the dragstrip brought some surprises. ?The Honda Nighthawk
isn't the fastest 550, with a best pass of 12.64 seconds and 102.27 mph.
That's about as fast as a 1982 GPz550 and not as fast as a 1983 Suzuki
GS550, even though the Nighthawk feels quicker than both.
The caveat here is that the Honda may be quicker than the Suzuki or
the Kawasaki, or at least may have the potential to be quicker. The
problem is that the 550's clutch is like other hydraulically-activated
clutches - using a master and slave cylinder connected by an
easy-to-route hydraulic hose - from Honda: grabby and imprecise. Add a
grabby clutch and a peaky engine without the torque of say, a VF750F,
and you've got a handful at the dragstrip. Ridden by the same rider, the
Suzuki is quicker than (and the Kawasaki about the same as) the Honda.
Both the Suzuki and the Kawasaki have cable-operated clutches with broad
engagement points and easy-to-modulate release.
As for top speed, the 550 reached 116 mph in the running half mile,
eight mph slower than the GS550.
That's as fast as the Nighthawk will go, since 116 mph equals 10,000
rpm (redline) in fifth gear. It won't go any faster in its extra-tall
sixth gear (Honda calls it Overdrive), and it will only go that fast in
sixth if the Honda is first run to the redline in fifth. Start
accelerating at 60 mph I sixth and the Nighthawk struggles to top 100
mph under the best conditions.
What we have in the Nighthawk is a typical 550's five-speed
transmission with an additional, taller cruising top gear added. Look at
the GS550 - it's also geared for 116 in fifth (top), happily revs past
redline to 124 mph in the half mile, and turns 5200 rpm at 60 mph. The
Nighthawk's tall sixth gear, on the other hand, is made for highway
cruising at a leisuerly pace, bringing engine rpm at 60 mph down to 4400
rpm from fifth gear's 5200 rpm.
Which makes it easy to understand why the Honda's top-gear
acceleration times are much slower than the competition. The Nighthawk
needs 6.6 seconds to accelerate from 40 to 60 mph in top gear (the GS550
takes 4.7 seconds) and 10.8 seconds to run from 60 to 80 mph in top (the
GS 550 needs 5.6 seconds).
At 60 in sixth, the Nighthawk is relaxed on the highway, but
accelerating quickly around slower traffic demands at least two
downshifts, and headwinds or upgrades often require fifth gear. Cruising
above 70 mph usually means spending more time in fifth than sixth gear,
which, despite the 550 having a lower primary ratio than the 650
Nighthawk, is close to being too tall for the engine.
The carburetors, which work very well at most engine speeds, have a
lean spot right at 4500-5000 rpm, the engine just a bit reluctant to
pull, hesitating when the throttle is rolled on in that range. It takes
full choke to get started in the morning, and at least half choke for a
mile or two before the engine warms up, even in the summer.
That stylish, sleek gas tank makes the rider pay for its looks with a
small, 3.2 gallon capacity. Under the best conditions, the tank holds
enough fuel for 153 miles before reserve. Typical riding demands reserve
after 120 or 130 miles, and the hardest open-road running saw the main
tank sucked dry in just 73 miles!
The steel frame is conventional, built to be inexpensive, a single
large backbone tube tied into the steering head with gusset plates, and
twin downtubes cradling the engine. The steering stem uses ball
bearings. The steel swing arm pivots on tapered roller bearings and uses
tow shock absorbers, which have spring pre-load adjustments only. The
leading-axle, air-adjustable front forks have a forged aluminum alloy
brace between the sliders, and there's a single hydraulic disc brake.
TRAC anti-dive is not used. Wheels are cast aluminum, a 2.15 x 19 inch
front and a 3.00 x 16 inch rear, and the rear wheel houses a mechanical
drum brake. The 550 is essentially a version of the 650. It is a little
smaller, the wheelbase measuring 56.7 inches to the 650's 57.5 inches,
thanks to a shorter swing arm. The 550 has 29 ° of rake (the 650 has
28.5°) and 4.2 inches of trail (the 650 has 3.9 inches). The 550 is
lighter, 440 lb with a half tank of gas, compared with the 650's 465 lb
with half a tank.
The 550's shorter swing arm has a couple of noteworthy effects.
Because the rider and the engine are closer to the rear wheel, the 550
is more liable to wheelie under hard acceleration than the 650. Because
the swing arm is shorter, stiffer shock springs and damping must be used
to control jacking of the drive-shaft rear end under power, and the
stiffer suspension is choppy over repetitive bumps.
The 550 has noticeable driveline snatch, especially at moderate
speeds around town. The light carburetor diaphragms, which do so much
for crisp, snappy response, are partially to blame here. The slightest
movement of the twist grip has an immediate action at the carburetors,
and any slack in the driveline is taken up instantly. There's a
spring-loaded, ramp-and-cam damper built into the driveshaft. The damper
helps isolate the transmission from road shocks but also contributes to
the slop in the driveline.
Anybody taking the 550 farther than the corner grocery will find that
the seat is hard enough to attract the rider's attention after 20 or 30
minutes. The seating position is much better than we've come to expect
of cruisers, the relationship between the pullback bars, the forward
footpegs and the stepped seat reasonably comfortable for most riders.
Despite being decked out as a cruiser, the 550's handling is as good
as its engine. It is stable, turns easily, and has good cornering
clearance - the footpegs touch first as an early warning system, and
then only during the most spirited riding. Pushed beyond that, the 550
wallows slightly in sweepers with a 150-lb rider, the result of
over-sprung, under-damped rear shocks.
Remember all those chromed and polished parts, such as the headlight
and its brackets and the instrument panel? Ride the 550 east during late
afternoon and all those polished parts reflect the sun into the rider's
eye, producing a terrific glare and making it almost impossible to read
the instruments. Under other conditions, the instruments are easy to
read, although they are prone to outrageous optimism. The speedometer
reads 60 mph at an actual 53 mph. All the usual lights are provided, the
headlight doing a fine job of illuminating the road, the
manually-canceling turn signal maintaining a constant tempo in the face
of changing engine rpm. The choke control is on the left handlebar,
right at the thumb's reach, rotating up and down. The control buttons,
such as the one for the reasonably-loud horn, are chromed plastic, as
are the screw-on covers for the fork air caps.
On the other hand, the helmet locks are nothing more than hooks under
the seat. To secure a helmet the rider must remove the seat, slip the
helmet's D-rings over a hook, and replace the seat. The battery must be
removed from its niche under the airbox before water can be added, the
air filter is hidden behind a cover secured by three screws, which is in
turn hidden under the right-hand plastic sidecover.
On the plus side, the rear wheel axle clears the mufflers and
removing the rear wheel isn't a major chore. And the Nighthawk's light
steering, narrowness and engine response earned I several weeks duty as
the commuter-of-choice for one man known to split lanes in bumper-to
bumper freeway traffic.
This 550 Nighthawk, then, is a combination of glitter and glitz and
solid function, providing a base of performance under all that style and
chromed plastic. It's proof that motorcyclists can have it both ways,
not giving up power for the cruiser look.
