Editing Yamaha TX 650-II

{{Infobox Motorcycle
|name             = [[Yamaha]] TX 650-II
|image            = [[File:Yamaha-TX650-77.jpg|frameless|Yamaha TX 650-II]]
|aka              = 
|manufacturer     = Yamaha
|parent_company   =
|production       = 1977 - 79
|model_year       =
|predecessor      =
|successor        =
|class            =
|engine           = Four stroke, parallel twin cylinder, SOHC, 2 valves per cylinder.
|bore_stroke      =
|compression      = 8.4:1
|top_speed        = 185 km/h / 115 mph
|power            =
|torque           =
|fuel_system      =
|ignition         = Battery, [[induction]] coil
|spark_plug       =
|battery          =
|transmission     = 5 Speed
|frame            =
|suspension       =Front: Telescopic forks <br>
Rear: Dual shock absorbers
|brakes           =Front: Twin [[hydraulic]] discs, 267 mm <br>Rear: Drum
|front_tire       = {{tire|3.50H-19 4PR}} 
|rear_tire   	  = {{tire|4.00H-18 4PR}} 
|rake_trail       =
|wheelbase        = 1435 mm / 56.5"
|length           =
|width            =
|height           =
|seat_height      = 810 mm / 31.9"
|dry_weight       = 191 kg / 420 lbs
|wet_weight       = 217 kg / 478 lbs
|fuel_capacity    = 15 Litres / 4.0 US gal
|oil_capacity     = 2.5 Litres / 2.6 US qts
|fuel_consumption =
|turning_radius   =
|related          =
|competition      =
}}

It could reach a top speed of 185 km/h / 115 mph.  

==Engine==
The engine was a Air cooled cooled Four stroke, parallel twin cylinder, SOHC, 2 valves per cylinder.. The engine featured a 8.4:1 [[compression ratio]].  

==Chassis==
It came with a 3.50H-19 4PR front [[tire]] and a 4.00H-18 4PR rear tire. Stopping was achieved via Twin hydraulic discs, 267 mm in the front and a Drum in the rear. The front suspension was a  Telescopic forks while the rear was equipped with a Dual shock absorbers. The TX 650-II was fitted with a 15 Litres / 4.0 US gal fuel tank. The bike weighed just 191 kg / 420 lbs. The wheelbase was 1435 mm / 56.5" long.  
== Photos ==
[[File:Yamaha-TX650-77.jpg|600px|Yamaha TX 650-II]]

== Overview ==
Yamaha TX 650























Source Cycle Guide magazine September, 1974 issue

This year's TX650 gets an A on its name...and a C+ on its
report card.

Multi-cylinder super-bikes have evolved into machines
that can handle almost as well as twin cylinder bikes, even though the
multis are wider, heavier, and have a higher center of gravity.  Even so,
heated debates still take place all around the world as to which design,
twin or multi, is the best.

All the pros and cons of multis have undoubtedly been
considered by Yamaha, but they have stuck to their twin-cylinder guns.
Instead of taking a big jump into a three- or four-cylinder touring machine,
they have elected to refine their present line of twins.

Since its inception in 1970, the Yamaha TX650 twin has
been battling for positive recognition.  It has sold well and has been one
of Yamahas most reliable models.  But the original XS-1 had some unusual
handling quirks that have been part of the bike since the beginning.  Some
riders never let the 650s wiggling and wobbling bother them; but others,
whose level of tolerance was much lower, confessed to never feeling quite
confident aboard a 650 Yammie.

This years 650, called the TX650A, has gone through some
frame and suspension changes that are major enough to qualify the chassis as
being all-new.  Yamaha made these changes in an effort to rid the 650 of its
unusual handling traits, which, in turn, would clear up any blemishes on the
bikes reputation.  Since the primary advantage of a twin is its supposedly
better inherent handling, the TX650 would not be considered a true success
until it overcame its inhibited road behavior.



THE BIKE:  Our test bike, the Yamaha TX650A, uses the
same basic powerplant as last years TX650.  The narrow, very tall engine
retains its slightly oversquare 75mm bore and 74mm stroke, which give it a
total displacement of 653.8cc.  The compression ratio has been lowered to
8.4:1.

Straight-cut primary gears transmit power from the
360-degree crankshaft to the large, multi-plate wet clutch and five speed
gearbox.  The gear ratios are close together and evenly spaced, so no big
rpm drops occur between shifts.

A single-row chain drives the overhead camshaft, and dual
30.6mm Mikuni-Solex constant-velocity carburetors supply the gas mixture to
the engine.  A two-piece airbox mounts under the front portion of the seat
and houses a pair of washable, oiled-foam elements.  Another piece of  foam
is placed behind each element to filter out the big pieces.  An easy
90-degree turn of the wing-nut knob on either side panel gains access to the
filters.

The Yamaha uses a conventional battery/coil ignition
system.  Dual breaker points mount at the left end of the over-head cam, and
a massive AC generator hangs on the left end of the crank.

A panel just in front of the handlebars holds the
speedometer (which reads nearly five mph fast at 30 and 60), tachometer,
ignition switch and idiot lights.



The 650 uses a double downtube frame that has a single,
large diameter backbone.  Heavy bracing and gusseting have been added to
this years frame to give it added strength and permit less frame hexing.

The bike has a sidestand on the left and a centerstand;
it doesnt take much effort to get it up on the centerstand, but you must
lean the machine way over to the right of center to get the sidestand down.
If you have short legs, or if youre standing on the left, the bike can
easily fall over on the right side while youre trying to get the sidestand
down.

The TX650A uses alloy rims at both ends, with a 3.50 x 19
Yokohama ribbed tire up front, and a 4.00 x 18 Yokohama universal on the
rear.  A double-action hydraulic disc brake stops the front wheel, and a
single-leading shoe drum brake gives the rear wheel its stopping power.  The
front forks allow 4.9 inches of wheel travel and the five-way adjustable
rear shocks permit 2.8 inches of rear wheel travel.

Chrome fenders, shocks, exhaust pipes, and chain guard,
contrasting with the matte black finish of the handlebar switches and
instrument panel, give the TX650A a neat, modern appearance.  The
four-gallon (last years was 3.7 gallon) Cinnamon Brown gas tank, side
panels, and headlight also blend in nicely, but the frame detracts from the
bikes otherwise clean overall appearance.  It has gussets supporting
gussets and frame tubes bracing frame tubes, all held in place by thick,
heavy welds.  Other than that, the machines workmanship is well above par,
and all the pieces fit together nicely.



ENGINE AND GEARBOX:


The TX650A has a wide range of usable power
which begins just above idle and lasts to engine redline at 7500 rpm.
It builds power smoothly and steadily and there is never a spot in the
powerband where the engine comes on all at once.  There arent any flat
spots throughout the range either.  The bike accelerates best between
4000 and 7500 rpm; maximum horsepower is at 7000 rpm, and the torque peaks
at 6000.



This steady pull gives you the feeling that the bike
isnt exceptionally fast. We were really surprised when it turned a
14.42-second quarter mile with a terminal speed of 92.2 mph. These figures
are close to those of some superbikes weve tested.





To start the engine when its cold, push down the
enrichener lever on the left carb, turn the key on, and push the starter
button.  After a few seconds of cranking, the engine comes to life.  Let it
idle for 30 seconds or so, lift the enrichener lever, and youre ready to
take off.  When the engine is warm, the procedure is the same, except you
dont need the enrichener at all.  There is also a kickstart system in case
of a failure in the electric start system, but it takes a healthy prod to
turn the engine over.



Last year the TX650 had a small lever on the handlebars
which was hooked to the starter motor and also operated an exhaust valve
lifter (which acted like a compression release).  Pulling this lever would
activate the starter and lifter simultaneously.  But the starter cranked the
engine over so violently that it often jerked the crankshaft flywheels out
of alignment.  Once this happened, the already-heavy engine vibrations would
become heavier.




The TX650A doesnt have the valve lifter this year, and
it uses a starter motor that transmits less torque to the crankshaft so the
crank stays in alignment.  But it sometimes takes three or four pushes of
the starter button before the starter gears engage.  The spring in the
Bendix starting unit is too strong and wont always allow the starter gears
to mesh.  The resultant clunking and whirring sounds are terrible.



The TX650A is tricky to get moving from a dead stop, so
you have to acquire the knack for smooth takeoffs.  This routine can be
attributed to a mild lack of flywheel effect and a short clutch engagement
span.  There is only three-quarters of an inch of lever travel from the
point where the clutch is disengaged to where its fully engaged.



For the smoothest starts, we found that revving the
engine to 1500 rpm and letting the lever out very slowly was the easiest way
and required a minimum amount of clutch slipping.  If the engine rpm was,
below this point, the bike would chug and surge and sometimes stall when the
clutch was engaged.  If the revs were above 1500, we had to hold the clutch
lever within this three-quarter inch engagement area until the bike was
moving about 10 to 12 mph.

Once youre underway, the engine wont let the bike run
smoothly below 10 mph.  It chugs and jerks, so you must continuously slip
the clutch to keep the engine from stalling.  This chugging is caused by an
excessive amount of slop in the drivetrain, the constant-velocity carbs, and
the lack of flywheel effect.



The Mikuni carburetors arent as temperamental as the
Keihin units on the TX500, but the bike idles erratically and often surges
when the throttle is held in one position.  Although we adjusted and
readjusted them, they still didnt perform perfectly.

Above 10 mph the engine works well;  if never wants to
chug or bog out unless the revs drop down below 1500.  There is plenty of
overlap between the gear ratios, so the engine rpm doesnt drop much between
shifts.  When youre in the hefty part of the powerband, its easy to stay
there.

The TX650A has enough power to cruise the freeways and
open roads easily.  There is enough reserve power in top gear to let you
move easily with the flow of traffic.  For the quickest acceleration to pass
slower vehicles you have to downshift once or twice to get the revs above
4000; but you can also pass comfortably in top gear.  At freeway speeds of
55 mph the engine is only turning an easy 3700 rpm in fifth gear or 4200 in
fourth.

If you like to play racer on winding roads, you dont
have to shift a lot to keep the engine above four grand.  Third gear lets
you run close to 80 mph without over revving the engine, and in fourth
you can go over 95 mph.

If youre riding into a headwind or up a steep grade, the
650 has plenty of mid-range torque available to churn out the miles without
the need to downshift frequently.



Yamaha found it necessary to redesign the cylinder head
cover for more efficient top-end oiling.  However, improperly designed
baffles in the cover let oil seep out the breather when the engine is
running; and when its stopped, oil that accumulates in the breather hose
falls to the ground.

We liked the gear ratios and overall gearbox operation
very much.  The shift lever travel is short, and the shifting was always
smooth and positive.  When the bike was new, we experienced some difficulty
finding neutral from first gear.  About 50 percent of the time we would miss
neutral and end up in second.  But shifting from second into neutral was
always a no miss proposition.  After the gearbox limbered up, this problem
ceased and we never again missed a shift.  The clutch took some punishment,
but it always acted like it should:  It never chattered or grabbed.



The TX650As gas consumption is one thing that could
hinder its long-distance touring.  We obtained anywhere from 35 to 42 mpg
during the test, with an overall average of 38.3 mpg.  This means the bike
can go about 150 miles between fill-ups.



HANDLING:  The frame has undergone some critical changes
to prevent the wobbling that existed on previous 650 Yamahas.  First, the
swingarm was lengthened an inch and beefed up for more strength and
rigidity.  The frame is now heavily gusseted around the swingarm mount,
steering head, and rear engine mount.  The engine has been moved forward
10mm and lowered 10mm to get the center of gravity lower and further
forward.  The steering head was lengthened slightly, and the fork offset
(distance between the steering shaft and the fork tubes) shortened by 13mm,
making this distance the same as on the TX750.  The TX650A now also uses the
same forks as the TX750.



The longer swingarm increased the wheelbase to 56.5
inches.  The 650 retains its 27 degrees of Steering Head Angle, but the
front wheel trail has been increased from 3.9 to 4.4 inches, due to the
shorter fork offset.  But even with these new frame changes, the TX650A
possesses a strange chassis combination that makes the overall handling
really different from the street bikes weve previously tested.



The TX is still a 474-pound heavyweight, and it is still
noticeably top heavy.  45.7 percent (217 pounds) of the weight rests on the
front wheel, and 54.3 percent (257 pounds) is on the rear.

The high center of gravity adversely affects the bikes
slow-speed cornering, low-speed maneuverability, and directional stability
in crosswinds.  As you go through a slow turn, the bike sits up slightly and
heads toward the outside of the comer when you open the throttle.  You must
make a small, quick steering correction to keep going where you were aimed.
The bike doesnt veer off course a great deal, but enough to be annoying.

Also, as you creep along in slowly moving traffic, you
must continually weave the handlebars from side to side to keep the bike
upright and going straight.  Often, even this steering technique wont work,
so you must dab with your foot to keep from tipping over.



On the road, crosswinds and gusts from passing trucks
make the TX tilt from side to side, often causing the bike to wander a few
inches off course.  With a full tank of gas, the center of gravity is
raised, and the bike wanders even further.

Yamaha stiffened the 650s front forks and rear shocks,
which successfully improved its high-speed cornering through smooth turns.
The bike never wobbled at high speed nor did it do anything unusual in these
turns.  You can pick a line through a smooth corner and the machine will
follow it precisely.



The footpegs and mufflers are higher this year, so we
could lean the bike over much further without encountering premature
grounding problems.  If you play racer and push the machine to its limits,
you will drag the footpegs when rounding smooth, slightly banked turns.
Through fast, flat corners, the sidestand will drag when turning left and
the muffler mounting bolt scrapes when going right.  If youre a more casual
rider, you can achieve reasonable lean angles without anything digging into
the pavement.



Both tires hold the road well, so there is never a worry
about them sliding out or losing traction unexpectedly when youre leaned
over.  At the lean angles the bike is capable of reaching, there is almost a
quarter inch of unused tire tread remaining.

The stiff forks and shocks are an asset for smooth
cornering, but if the turn is bumpy or rutty, you must pay close attention
to where the bike is going.  The suspension units on our test bike were
insensitive to these small bumps and caused the machine to change direction
slightly in the turns. Instead of absorbing the bumps, the suspension caused
the bike to veer off course.  The change in direction isnt violent, but you
must make small, deliberate steering corrections to keep the bike going
where you want it to go.



The TX650A cruises along smooth highways and open roads
nicely.  You can change lanes quickly and predictably, and zip in and out of
traffic with ease.

But on rain-grooved freeways, the front end has a
noticeable wiggle, and you must make a conscious effort to keep the bike
going perfectly straight.  This wiggle is due in part to the ribbed front
tire, which tends to follow the wavy, combed pattern on the road.  On
twisty, mountain-roads, the TX650A handles best if you glide it through the
turns with a gradual, smooth motion.  You cant charge up to a corner and
flick the bike over at the last moment because it responds slowly to such
treatment.  If you try to manhandle it around corners, it resists.  If you
use a gentle flowing motion, the bike swoops around these same corners
gracefully.



Some TX650A owners and Yamaha dealers told us that the
bikes suspension was stiff when new, which sometimes caused some of these
handling peculiarities.  They claimed that the bike handled and steered
quite differently once the suspension softened up slightly.  Our test bike
had a stiff suspension, so we went to a local Yamaha shop and borrowed
another TX650A, one with over 5000 miles on it.  We wanted to find out for
sure which of the handling quirks were caused by the stiff suspension, and
which were related to the high center of gravity.

We found that the softer suspension on the borrowed bike
had the ability to soak up bumps more efficiently, so cornering through
rough turns was more precise and unaffected, and the need for small steering
corrections didnt exist.  And surprisingly, the cornering Ground Clearance
was just as good with the soft suspension.  We could tilt it over just as
far as our stiffly-sprung test bike, and it felt just as stable.

The other handling idiosyncrasies, the ones
caused by the high center of gravity, were the same on the borrowed bike as
on our test machine.



The borrowed 650 felt top-heavy around slow
corners, was awkWard at slow speeds, was affected by gusts of wind, and
responded best to a gradual approach into a hard turn.  And since it
had a ribbed front tire it too wiggled in the rain grooves.



COMFORT AND RIDE:  For hour-long trips, the TX650A is
comfortable; but on longer jaunts, it becomes very uncomfortable, mainly due
to the thinly-padded seat.  The seat is hard and slants down at the front,
so as you ride along, your body gradually moves toward the gas tank. In this
area, the seat padding is thin and doesnt offer much support.  You can feel
the seat base pushing on your rear end, and after a short while you feel
some saddle sores forming.  If you move back on the seat, theres a little
more padding, but still not enough to be really comfortable.  The stiffness
of the suspension made the hardness of the seat even more annoying.  The
inability of the forks and shocks to absorb small bumps and ripples caused
the bike to bob up and down, which hammered the seat against our butts.  On
our test bike this was very aggravating: but on the borrowed 650, the
broken-in suspension was considerably smoother.  Solo riding on the borrowed
bike was just about as smooth and comfortable as two-up riding on the test
bike-and that wasnt bad at all. And even though the suspension on our test
bike is insensitive to small-and medium-size bumps, strangely enough, they
absorb big jolts fairly well without transmitting much shock to your body.



The handlebar/footpeg/seat relationship is fine for
people shorter than 5' l0", but some long-legged riders will find it a bit
cramped. The handlebars are high enough and have a nice rearward rake, but
youll find yourself sitting in a squat position, with your knees high and
sharply bent. This eventually makes you uncomfortable and restless.

Engine vibration also has a negative effect on the
TX650As comfort. You get a tingling sensation through the hard, thin
handgrips, and through the rubber-covered, rubber-mounted footpegs; but the
largest amount of vibration comes through the seat.



The 650 has two rpm ranges where the vibration is most
pronounced. The first occurs from 1500 to 2500 rpm; it then becomes
negligible from 2500 to 3500 rpm. Then, from 3500 until redline, the vibes
steadily increase as the revs get higher. The mirror is only useful in the
2500 to 3500 rpm range; at all other rpm, its wasted. Its hard to tell if
youre being followed by a bus or a compact car.



One nice thing about the TX is its quietness. There is
very little mechanical noise produced by the engine, and the note from the
mufflers is a deep, throaty one. Our decibel testing showed that it produces
only 86.3 db (A), so you wont offend any citizens with loud, unwanted
noise.



BRAKING:
The Yamahas front disc brake worked perfectly and consistently
during the whole test. It required only a two- or three-finger pull on the
lever to bring the bike to a stop, and it never wanted to lock up the front
wheel.

Although the rear brake isnt very powerful, it does an
adequate job of stopping the rear wheel. You have to press hard on the brake
pedal to stop the bike, so you should never lock the rear wheel
accidentally.

The brakes work nicely during panic stops. Theyre
progressive and stop the bike quickly and predictably without fading. The
bike also doesnt get sideways or out of shape when both brakes are full on;
it stops in a straight line every time.

From 30 mph, we got the TX to a screeching halt in 37
feet 1 inch, and from 60 mph, it took 137 feet. The testers never felt
apprehensive about using the full stopping power of the brakes because they
worked so predictably. A beginning rider will also find the brakes reliable,
consistent, and easy to use.



RELIABILITY
DURING TEST: We
were very pleased with the TX650As reliability. The machine spent some
punishing hours at the dragstrip and on the dyno, plus many miles on the
streets and highways.  Nothing broke, fell off or stopped working, and
thats what reliability is all about.

The clanky starter and the oil leakage from the breather
are problems that Yamaha is aware of.  They are currently in the process of
working out factory modifications, which will soon be available at no cost
to all TX650A owners.



SUMMARY AND CONCLUSION:  The TX650A has a rugged, quiet
engine that produces a wide band of usable power ranging from 2000 to 7500
rpm.  Once over 10 mph in first gear, it pulls steadily and strongly all the
way up to top speed.  The close-ratio gearbox provides even gear spacing,
and a short, positive lever throw.

The handling is unusual, with a high center of gravity
that makes the bike feel top-heavy in slow turns, awkWard while maneuvering
at walking speeds, prone to be affected by sidewinds, and reluctant to be
tossed into a hard corner too quickly.  When the TX650A is new, the forks
and shocks are stiff, causing the bike to skip around and change direction
while cornering on ripply or mildly choppy pavement.  After the suspension
has a few thousand miles to loosen up, the 650 corners more precisely on
these same turns.  And smooth, high speed turns create no problem, either
when the bike is new, or after the suspension wears in.



The seating position is fair, the seat is hard, and the
ride is bumpy when the bike is new.  Again, after the suspension settles a
bit, the ride is much better, but the seat still doesnt offer much
long-range comfort.  The vibration of the engine can be felt through the
handgrips, the footpegs, and especially in the seat.

The brakes are progressive and easy to use, the bike
stops in a straight line, and the only reliability problems we encountered
were two that the factory is aware of and in the process of rectifying.



Yamaha has done some of their homework, but not all of
it.  The bike still feels very top heavy, which affects the handling quite a
lot.  And if, for some reason the suspension on a new 650 should fail to
soften up after a couple thousand miles or so, the owner will be in for many
long miles of frequent erratic cornering and rough riding.  And although the
level of vibration is lower than on previous 650s, this bike cries out for
Yamahas Omni-phase balancing system, which could lower the vibration to a
level more in line with current standards.

The TX650A has the potential to be a true sporting bike
in the tradition of the British twins that it originally copied.  It has
bettered these bikes in many areas -- electrics, electric starting, oil
retention, reliability and ease of maintenance.  But if theres one thing
that these almost-extinct British bikes have going for them, it is
near-impeccable handling, and in that respect, the Yamaha should have to
stay after school for some extra lessons.
Source Cycle Guide magazine September, 1974
issue
{|  class="wikitable"
|- 
!Make Model
|Yamaha TX 650-II
|- 
!Year
|1977 - 79
|- 
!Engine Type
|Four stroke, parallel twin cylinder, SOHC, 2 valves per cylinder.
|- 
!Displacement
|653 cc / 39.8 cu in
|- 
!Bore X Stroke
|75 x 74 mm
|- 
!Compression
|8.4:1
|- 
!Cooling System
|Air cooled
|- 
!Lubrication
|Wet sump
|- 
!Induction
|2 x Mikuni carburetors
|- 
!Ignition
|Battery, induction coil
|- 
!Starting
|Electric and kick
|- 
!Max Power
|39.5 kW / 53 hp @ 7200 rpm
|- 
!Max Torque
|54 Nm / 5.5 kgf-m / 39.8 lb-ft @ 6800 rpm
|- 
!Transmission
|5 Speed
|- 
!Final Drive
|Chain
|- 
!Front Suspension
|Telescopic forks
|- 
!Rear Suspension
|Dual shock absorbers
|- 
!Front Brakes
|Twin hydraulic discs, 267 mm
|- 
!Rear Brakes
|Drum
|- 
!Front Tire
|3.50H-19 4PR
|- 
!Rear Tire
|4.00H-18 4PR
|- 
!Dimensions
|Length: 2175 mm / 85.6"Width: 780 mm / 30.7"Height: 1090 mm / 42.9"
|- 
!Wheelbase
|1435 mm / 56.5"
|- 
!Ground Clearance
|150 mm / 5.5"
|- 
!Seat Height
|810 mm / 31.9"
|- 
!Dry Weight
|191 kg / 420 lbs
|- 
!Wet Weight
|217 kg / 478 lbs
|- 
!Fuel Capacity
|15 Litres / 4.0 US gal
|- 
!Average Consumption
|5.0 L/100 km / 20 km/l / 47 US mpg
|- 
!Oil Capacity
|2.5 Litres / 2.6 US qts
|- 
!Top Speed
|185 km/h / 115 mph

|}

[[Category:Yamaha motorcycles]]