The first RD350 model introduced in 1973 was a
347cc, two-stroke twin, featuring a seven-port engine with Torque Induction.
It had Yamaha’s Autolube lubrication system, which meant no pre-mixing of
the gas and oil, a primary kick starter and a 6-speed constant mesh
transmission. It also sported some neat features of the period such as a
steering damper, stop lamp outage indicator, and a panel type
instrumentation dash. Front wheel disc brake was standard as well.
By 1974, the RD 350 had already earned a spot in the hearts and minds of
sport-bike riders who really appreciated its nimble handling and responsive
two-stroke engine. It was nicknamed in some circles, “The Giant Killer” for
its overall performance against much larger machines.
In 1975, the RD 350 was the biggest version sold
and its list of loyal riders grew with every passing year. The RD 350 was
dropped at the end of the model year of 1975, and in 1976, Yamaha introduced
the RD400, increasing the stroke of the little RD 350 to 399cc. The US
market was changing due to pollution issues but Yamaha decided to move
forward with the larger RD400. In 1979 came the RD400F and then, a limited
special edition series called the Daytona Special were sold. These are now
highly collectible
New for 1984 was the RZ350L, and this model was targeted at buyers who
missed the powerful little two-stroke street machines of years gone by. For
the 1984 release, Yamaha used a much cleaner and quieter engine, and this
time it was liquid cooled. The trick yellow and black Kenny Roberts paint
did not sell well in Europe, but was a big hit in the USA for obvious
reasons. In 1987, the RZ350 was pulled and would not return.
Road Test 1974
Charles Darwin's island animals could not have
followed a more clearly defined course of evolution than have the 350 Yamahas. A
line of fairly well adapted and very well established 250s have watched new
generations of bigger brothers first mutate ever so slightly into 305s and then
to full 350s.
From the primordial soup of German Adlers, whence
came the first Yamaha twins, it was almost impossible to distinguish between
racing and touring as parent/child. In 1967 Trevor Deeley, then the Canadian
Yamaha Importer, brought to the Indy National a 350 road racer that had been
converted from a 250 in his shop. Before the bike expired with a terminal case
of teething bothers, then little-known Yvon duHamel had unceremoniously raced it
through the pack and momentarily passed the race-winner, Cal Ray; born, on his
750 Harley. A lot of people either didn't see that historic event or refused to
believe their eyes. The unbelieving were given another demonstration at the
following Spring's Daytona: Mike Duff qualified a 350 second-fastest at over 147
mph, and two other Yamahas finished the race in second and third places behind
Rayborn's big H-D. So it has been ever since: Yamaha 350 racers have been
beating bikes with engines twice as big and the street counterparts have gotten
better and faster just as steadily.
A first, even casual ride immediately drives home
the essential nature of an RD 350B. It is stiff and taut and at times has a
shade of race-bike reluctance. The first display of this reluctance is met in
the engine's starting. Or perhaps it simply is more lethargic than reluctant.
Two-strokes get twitchy during starting when the carburetor mixture is not rich
enough or if there is not enough of it. Mikuni blessed the world of the
two-stroke with a completely separate metering system for cold-engine starts.
Most Japanese bikes have one of these cold-start systems in each carb. But
Yamaha embraced economy and simplicity by using a cold-start device only in the
left carb and connecting it to the right carb with a length of hose.
When the starting device is actuated by a thumb
lever on the left carb, the Yamaha is ready to start after the ignition switch
(conveniently located between the instruments at the handlebars) is on and the
fuel valve handle is vertical. Normally a Mikuni-equipped two-stroke will fire
immediately if the throttle is left completely closed. But the siamesed system
does not provide enough mixture to easily rouse both cylinders. This causes the
rider to have to alternate between closed and barely-opened throttle until the
engine catches and clears. On a brisk morning, we found that the best procedure
was to push the kickstart pedal through four times to prime the shared system
and then crack the throttle slightly when the engine sounded ready. The number
of engine revolutions per kickstart stroke is relatively high, so the pedal
resistance is considerable. But not so great one has to leap up in the air
before each try, as with a big four stroke.
Once the engine cold-naturedly coughs to life, it
remains balky but does not attempt to die unless the enriching lever is
prematurely closed. Pre-dawn staggers fade quickly with the light of engine
heat, however, and exhaust sound steadies into a romping, insistant,
bramp-bramp-bramp that is strongly reminiscent of the first 500 Kawasaki
triples. One can't simply motor away smoothly on an RD 350B: the revs must be
held at about 3000 while the clutch is gradually engaged to couple the
transmission and engine. At about 4000 rpm the engine begins to cackle along
happily at constant throttle. Twisting the throttle open in low gear produces a
gradual, easily controllable wheelie. A full-power shift to second brings the
wheel back up about a foot. Through third and into forth gets you to 60 mph in
less than five seconds and the scenery is beginning to blur at the edges. In
just over 14 seconds, the bike is approaching its rpm red line and is hurtling
along at over 90 mph. The tach needle easily touches 8000 rpm in high gear
(sixth!) and you back off the throttle to keep the engine from fragging itself.
So little noise and vibration accompany such a
spurt that the rider must -rely on his feel of accelerative force and visual
judgment to perceive how quickly he has attained a high rate of speed. It is
extremely unusual for a high-performance bike to be so smooth and quiet. The
lack of commotion makes the speedometer and tach readings difficult to believe.
Blasting along twisty, deserted roads proves the
RD 350B's suspension to be almost as good as the engine and gearbox. Both the
forks and rear shocks have high damping rates to control the rebound movement of
their springs. The front springs are stiff, and keep the front of the bike from
diving far enough to cause sudden clearance problems when the throttle is closed
approaching a downhill curve. Three possible preload settings are provided on
the rear shock springs and the stiffest setting was required to match the fixed
fork preload for our 160 pound rider. Thus adjusted, the machine will not
oscillate in high-speed sweeping turns.
Ground Clearance is limited by the steel footrest
mounting bars. These bars hit just after the ends of the rubber footrest rubbers
drag on flat turns, but give no warning before sending the sparks flying on
hog-back curves. Fairly hard riding is required to find the clearance limits.
The standard Japanese Dunlop tires are much
better than the rubber that usually comes on 350 street bikes. A ribbed-pattern
front (3.00-S18) gives extremely sensitive steering response with almost neutral
feel through the handlebars. Dunlop's designation for this tire is F7. The rear
tire has a universal pattern, is designated K95, and the size is listed as
3.50-S18. We have as yet to hear an official explanation for the new S sizing
designation, but the tires seem to have a wider tread profile for a given
cross-sectional carcass size as compared to conventionally proportioned tires.
The K95 rear gives first-rate directional stability and allows plenty of
cornering traction within the bounds of the clearance dictated by the footrest
bars. When traction does get scarce, the tire begins to feel crawly and the rear
end of the bike slides predictably.
During fast road riding and our instrumented
braking tests at the drag strip the brakes performed completely without fault.
The rear has a good, strong, progressive feel and the front disc is absolutely
incredible. Until we got this year's RD 350, the quickest stopping bike we had
ever instrumented was last year's RD 350 in a stop that corresponded to an
average g-force of .998. Thanks to the nice wide footprint laid down by the
front tire, and the tire's unwillingness to distort laterally, this year's model
established a new record by decelerating at an average rate of 1.04 g from a
true 60 mph to a complete stop. A good hard squeeze is required to keep the
front tire on the verge of locking, but you don't have to pull so hard that no
sensitivity remains to monitor the possible consequences. Nothing unusual about
the brakes was noted during the test other than their ability to stop the Yamaha
in the shortest 60-0 mph distance we've ever recorded.
The combination wrought of the stiff suspension,
good street tires, and fairly neutral steering geometry of 27.5 degrees rake,
4.17 inches trail, and a rather short 52-inch wheelbase gives the RD 350B a very
precise but quickish feel that is underlined at all times with unshakeable
stability. The rider can feel every pebble and seam in the road but quickly
learns to ignore them. This stability and sure-footedness combine with perfect
body-to-bike fit to leave one's senses free to experience the rush of wind and
road.
When the six-speed gearbox was introduced in the
Yamaha 250s and 350s three years ago, many of us figured it was merely a ploy to
legitimize the arrangement for the purpose of AMA-ruled racing. And such may
have been the case, for many countries still get five-speeders as the standard
retail fare. But ploy or not, the six-speed gearset gives an RD 350B the extra
dash of the spice of performance that transforms it from a mere sporting
middleweight into a genuine middle-weight Superbike. An examination of the
performance chart will show that the standard gearing is set for the engine to
just peak in high gear at the end of a quarter-mile. The six speeds allow the
engine to keep within its most efficient rpm range from a tire-smoking start to
the peak in high. The result was best quarter-mile run of 14.12 seconds at 93.21
mph. Those figures utterly overshadow any generated by the Yamaha's immediate
price/engine-size competition and put the RD 350B on performance-par with many
650s and 750s.
Back out on the country roads, the right gear is
always available to prevent any instances of the dread Lazy Tach Needle. Any
time the rider gives the grip a twist with the tach reading between 5500 and
7000, a really gratifying surge of acceleration is right there, ready and
waiting.
Several aspects of the RD 350B's character make
it rather compromised as a general transport mount. The stiff forks and shocks,
which gave good cornering control at high speeds, also provided our 160 pound
rider with punishing jounces from freeway seams. A 200 pounder found the bike
too soft on the country backroads and about right on the freeway. Our 130-pound
art director developed eyeball-rattle and split vision either place, because for
him the springs wouldn't yield at all. True progressive-rate springs in the
forks and shocks would be the answer, but the cost and manufacturing difficulty
involved in making the springs will keep them from being standard equipment. The
big and little RD 350B owners will be obliged to hunt out fork and shock springs
to suit their own needs.
The engine also contributes a bit toward everyday
touring bothers. A combination of the highly-tuned cylinder breathing and a pair
of genuine low-quality ignition coils give the bike a high rpm misfire that is a
cause of some concern when there is a loaded gravel truck to overtake in the
only passing zone for 20 miles. Yamaha's specified spark plug for the RD 350B is
an NGK B8HS, which is supposed to have a very wide heat range electrode. If the
plugs are new, they function okay for a while. But after a day's normal
cruising, enough deposits built up on the plugs to cause the had misfire when
the rider downshifts to make a full-throttle pass. We fiddled around with the
engine for a couple of days trying to trace the malady to its source. A look at
the ignition coil output trace with an ocilloscope showed that the output
voltage of the coils is about 40 percent below what is delivered by a normal
automotive coil. Our scope is not designed to give kilovolt readings in numbers,
but it does a good job of comparing coils. In such a situation there are a
couple of immediate solutions: increase the spark voltage by changing the coils,
or decrease the spark plug resistance. The plugs were not excessively oily or
fuel-fouled so it wasn't simply a case of installing a hotter heat range.
Several of the spark plug manufacturers make a special group of plugs for
two-strokes which have fine-wire center electrodes composed of an alloy (gold,
palladium, etc.) which will cause a spark to jump a given distance at a
considerably lower voltage than conventional plugs.
We use Champions in our shop because that
company's local field representative can supply solid information and plugs in
any size, type or heat-range. Champion L-3G plugs allowed the Yamaha to start
easier and run under varied conditions for three weeks without once misfiring.
So what's the big deal, you ask. Just screw in
the jazzier plugs, go on your way and stop ranting. It is no big deal, really,
we suppose. But the economics involved are a classic example of any
manufacturer's constant vacillating between cost-savings and quality. Better
coils which would fire normal sparkplugs would cost the manufacturer maybe an
extra buck each. And the unobtanium-alloy plugs cost the bike's owner that much
extra each time he changes to a fresh set. That leaves the coil manufacturer and
the spark plug maker pointing the finger of blame at each other, with the biker
somewhere in between. If an extra dollar were spent on very many of the bike's
critical components, it could sell for twice its present price. And that price
is already overblown beyond recognition, as we will see later.
It really is grossly unfair to niggle about the
quality of the coils for so long. There are many components on the RD 350B which
are excellent. The alternator is the excited-field type, which means that its
output is governed by the rate of battery drain. No fuel-eating power is
generated without being used. With a capacity of 160 watts, the alternator is
more than capable of powering the high—output coils that are put on the RD 350s
by those who run them in production races. And finally the Yamalube automatic
oil metering pump meters the prescribed amounts to each carburetor instead of on
the street, garage floor, and rider's shoes as did many in recent years. The
instruments are reasonably accurate, the finish quality is good, and the seat is
just that right combination of resiliency and firmness. Our only real
reservation about any of the RD 350B's external fixtures concerns the
gonad-gouger Yamaha has made of the bike's locking gas cap.
As indicated by the performance figures and our
comments about smoothness and relative quietness, we think that the Yamaha 350
twin engine has become a mature and settled powerplant, while by nature and
heredity remaining a hard-nosed hotrod. Nonetheless, quality control problems
still arise at times. Our first test bike suffered a big power loss when its
second ring seized to the piston. The replacement was a rocket that fizzled only
when ignition demand exceeded coil output.
As all enthusiasts who have visited a dealer's
showroom this year have noted, the price of bikes (especially Japanese' bikes)
has soared. Last year the price of a RD 350 was $839: now ,the virtually
identical RD 350B is a staggering $121 1. But everything is relative. That price
will buy you a stiff-legged road-sports machine whose engine produces almost 100
brake horsepower per liter of piston displacement, whose 10.35 lbs. per brake
horsepower (at curb weight) make it accelerate with an authority that belies its
displacement, and whose magnificent brakes will stop harder than every other
vehicle on the street. If the cruel clutch of inflation has grasped you less
firmly than most, buy an RD 350B for the ride of your life. And complain like
hell about any little faults that show up until the dealer fixes them.
One last thing: if the kind of performance
described above appeals to you, and if you think a 350cc-sized motorcycle will
feed your particular rat, you better buy an RD-350B some time soon. Hot, perky
two-strokes have a way of producing unburned hydrocarbons that the Environmental
Protection Agency finds unattractive. When and if smog legislation is enacted,
you can bet your bottom dollar that hi-perf two-stroke street machines will be
the first to drop. So get one, as they say, while they're hot. It might be your
last chance.
Any corrections or more information on these motorcycles will be kindly appreciated.