Editing Yamaha XJ650 Seca

{{Infobox Motorcycle
|name             = [[Yamaha]] XJ650 Seca
|image            = [[File:Yamaha-XJ650G-80--1.jpg|frameless|Yamaha XJ650 Seca]]
|aka              = 
|manufacturer     = Yamaha
|parent_company   =
|production       = 1981
|model_year       =
|predecessor      =
|successor        =
|class            =
|engine           = Four stroke, transverse four cylinder, DOHC, 2 valves per cylinder,
|bore_stroke      =
|compression      = 9.2:1
|top_speed        =
|power            =
|torque           =
|fuel_system      =
|ignition         = Transistorized
|spark_plug       =
|battery          =
|transmission     = 5 Speed
|frame            = Tubular steel dual cradle frame
|suspension       =Front: 36mm Kayaba forks <br>
Rear: Duel Kayaba shocks
|brakes           =Front: 2x 268mm disc 1 [[piston]] [[calipers]] <br>Rear: Drum
|front_tire       = {{tire|3.25-19}} 
|rear_tire   	  = {{tire|120/90-18}} 
|rake_trail       =
|wheelbase        = 1445 mm / 56.8 in
|length           =
|width            =
|height           =
|seat_height      = 780 mm / 30.7 in
|dry_weight       = 206 kg / 465 lbs
|wet_weight       =
|fuel_capacity    = 19.5 Litres / 5.1 US gal
|oil_capacity     =
|fuel_consumption =
|turning_radius   =
|related          =
|competition      =
}}



==Engine==
The engine was a Air-cooled cooled Four stroke, transverse four cylinder, DOHC, 2 valves per cylinder,. The engine featured a 9.2:1 [[compression ratio]].  

==Drive==
Power was moderated via the Wet Multiplate; 7 Steel 8 Friction.  

==Chassis==
It came with a 3.25-19 front [[tire]] and a 120/90-18 rear tire. Stopping was achieved via 2x 268mm disc 1 piston calipers in the front and a Drum in the rear. The front suspension was a  36mm Kayaba forks while the rear was equipped with a Duel Kayaba shocks. The XJ650 Seca was fitted with a 19.5 Litres / 5.1 US gal fuel tank. The bike weighed just 206 kg / 465 lbs. The wheelbase was 1445 mm / 56.8 in long.  
== Photos ==
[[File:Yamaha-XJ650G-80--1.jpg|600px|Yamaha XJ650 Seca]]
[[File:Yamaha-XJ650G-80--4.jpg|600px|Yamaha XJ650 Seca]]
[[File:Yamaha-XJ650G-80--2.jpg|600px|Yamaha XJ650 Seca]]
[[File:Yamaha-XJ650G-80--3.jpg|600px|Yamaha XJ650 Seca]]

== Overview ==
Yamaha XJ 650 Seca






















Okay, might as well get the grovelling over first. Those of you who had the
undeniable good taste to buy last month's ish may have noted a pious hope that
we'd be testing Honda's CX650 this time round. Ahem. Well we near/ytested it.
Enraged and infuriated beyond reason during yet another fruitless trip to Big
H's UK HQ in search of an increasingly elusive VF750F (see last ish for that
particular tale of disappearing Hondas), I commandeered a CX with the intention
of holding it hostage.
Alas, a park keeper with hismindon things herbaceous forced another staffer
into a conflict situation with some wheelbarrows by attempting a U-turn in front
of the CX in his van. Luckily only minor damage was incurred by barrows or Honda
but, while the barrows were doubtless quickly patched up, the Honda was
sidelined by a small scratch on its flyscreen. And where was the vitaK?)
replacement part? In Ghent . . .which, before you reach for your atlas, is
definitely not in this country. No CX650.
Frantic 'phone calls were made to the Other Importers, the result being
someone else's shaft driven 650cc four-stroke  to whit an XJ650. And this time,
of course, with YICS. YICS, as well as being the Mongolian word for 'no', is
short for Yamaha Induction Control System. Unless you've actually been in
Mongolia these last three years, saying 'yics' whenever offered a pint of goat's
milk beer, you'll doubtless know that YICS is essentially a no-moving-parts
add-on to the intake side of Yamaha four-stroke motors aimed at improving
combustion efficiency and fuel economy.
It consists of a pipe running across the rear of the cylinder head from which
four small passages run up to the main inlet tracts, which they join just behind
the valves. As each piston starts its induction stroke it sucks mixture from
both the main and YICS inlets. As the YICS inlet is a much smaller diameter than
the main one, the mixture travels up it at a faster rate and, on meeting the
main charge, gives it a swirl as it spills into the combustion chamber. Yamaha
reckon the system's a good 'un when it comes to getting good power and
gas-mileage without the complication of using four valves per cylinder. And to
be honest, good power and gas mileage were not the original X|650's strong
points . . .
The X), you'll maybe recall, was billed as Yamaha's answer to those hacks and
punters who persistently decried the japs for bowing only to the tastes of
American riders bent on cruisin' evil, wobbly, chain-consuming, gas-guzzling
megalumps down Interstates at 55mph. Feedback was in the in-word in 1979/80;
Yamaha NV in Holland went in for some heavy polling of Eurobikers as regards
their taste in machinery. The results were fed back to Japan where the designers
were contemplating Yamaha's first new four-stroke multi since the XS750/850 and
Excess Eleven.
The upshot, it transpired when first details were released, was a
nice-looking, no nonsense 650. Low, slim, shaft-driven, unencumbered by
complicated suspension or digital widgits, it sounded both sensible and fast 
especially with a claimed 73bhp on tap. Reactions to the XJ650 when it arrived
were, however, mixed. Good marks were handed out for comfort and performance,
medium points for transmission smoothness and handling, and rotten ones for
power characteristics and fuel economy.
Yamaha's answer was to add YICS last year, along with dropping the rather
tasty silver paintwork of non-induction controlled models for a rather heavy
handed metallic blue. The only other changes I could see on the test X| I
collected from Chessington were new indicator lenses and something more up to
date in the way of Bridgestone rubber on the cast italic wheels.
Seen as a good-looking bike a couple of years go, the XJ's styling has been
left behind by the tide somewhat. Or maybe  sudden thought it's actually jap
late-'70s-classic. That outsize 8in H4 headlamp and separate chromed instrument
housings above an unfashionably large 19in front wheel hardly cut it with the
GSX/GPz/CBX mob with their integrated fairings, tanks, seats and tails. On the
other hand I'll bet the Yamaha's cheaper and easier to repair after a spill.
When cold the motor fires up easily with a little help from the choke, whose
lever is conveniently positioned under the left handlebar switchgear cluster.
Despite the sparse finning on the head and barrels and close-set pots, the motor
takes quite a while to warm-up fully: it'll pull away after a few seconds so
long as some choke is left on but on a cool morning it takes a few miles before
the XJ'II run smoothly and cleanly. On the other hand the motor gets very hot on
really warm days (do we ever get those any more?) so maybe the five-row oil
cooler isn't just a gimmick.
A peculiarity of the XJ series is the use of oil level warning lights instead
of the more usual oil pressure  maybe Yamaha have loads of oil level switches
left over from the 2T lube tanks of RD strokers they don't build any more . . .
The red oil idiot light flickers briefly when the starter button's pressed to
show it's working but there's a sight window below the clutch cover for a visual
check  except in cold weather when it mists up with condensation on the inside.
Once running the one truly unique feature of the XJ650 manifests itself.
Instead of emitting the usual four-stroke, four pot threshing and grinding
noises, the mill puts out a penetrating high-pitched whistle guaranteed to turn
pedestrians' heads at up to 200 yards (183 metres). If you've only bought an XJ
as a humble, low maintenance workaday hack it gets pretty embarrassing when
folks start staring at you as if you're on some freaky turbo. On the other hand
the XJ does sound a bit like a jet fighter barrelling up a runway if that's the
way your fantasies lie. It's hardly relaxing, though,  even at a steady 60mph
and 4250rpm the XJ's lump sounds like it's turning a coupla zillion revs, which
is okay on a cruise down the Kingston bypass but begins to grate on a 200-mile
trip. Only thing to do is keep the thing at 90mph or more where wind noise and
other mechanical rumblings drown out the whistle. Like so many things about the
XJ650, you either learn to put up with it or find another scoot. The weirdest
thing about the engine note is the effect on it of a slight misfire (which
usually manifests itself if moisture gets into the plugs' metal suppressor
caps), whereupon the whistle becomes a bubbling noise very akin to the sound of
someone farting in a bath.
One aspect of the XJ which definitely doesn't have to be just tolerated is
the seat and riding position. The seat is flat and firm; very comfortable over
long distances and easily large enough for two fatty posterior regions.
Footrests are slightly rearset  not quite far enough back for sustained high
speed bashes but comfortable enough for normal use up to around 80 per. Together
with shortish, down-curving LC-type bars, the seat and pegs make for all-day
comfort.
If you take the XJ's sweet shaft drive and ample provision for hard and soft
luggage stowage into account as well, the foregoing sounds as if it's a
reasonable touring proposition. Unfortunately the character of the original XJ's
motor was almost completely at odds with most people's idea of the compleat
tourer's powerplant.


Like most high horsepower middleweight fours, the XJ engine needed plenty of
revs to find significant power. Most of what you'd call exciting performance
comes in around seven grand and runs up to the 9000rpm mark. After that it's up
to wind, gradient and crouch to determine whether it'll stop pulling or run on
past 9'/2 thou and into the red zone. Lower down the original version's rev
range, there was an area of useful poke between 2500 and 5000rpm: below that it
gasped at a handful of throttle and above it the motor felt pretty flat until
seven grand.
Translated into road terms, it meant the old bike possessed adequate but not
startling performance in top (fifth) gear up to about 70mph and then took its
time to reach 90. In first gear, especially when hot, mucho revving and clutch
slip was necessary to avoid fluffed getaways from lights. Fast travel was a
mixture of twist-grip wrenching, incessant gear changing and, if the revs
dropped into the midrange snooze zone, waiting. Hard charging with max use of
throttle and gear pedal disguised the lumpy powerband but the trade-off was fuel
consumption down in the 30s and, of course, colossal amounts of whistling and
fussy noises down below.
It'd be nice to report that adding YICS has transformed all that. But I
can't. It has made a few subtle improvements: the motor's less asthmatic at very
low revs and the midrange power trough isn't so noticeable but the power
gradient is still uneven. Fuel consumption is improved, however. A
100-mile thrash to MIRA on A roads, holding 90-100mph most of the time, followed
by a couple of dozen miles of redlining abuse at the track pushed consumption
down to lever you push in to cancel manually.
The seat hinges up rather than lifts off; a short rod holds it up. A typical
lap toolkit sits in a tray over the airbox and contains enough spanners and
alien keys for simple servicing and wheel removal. The plastic coated security
chain squeezed into a compartment above the swing arm pivot won't deter anyone
with a decent set of bolt cutters but it's useful for chaining helmets to a
wheel while you go shopping or whatever.
The 4.3gal tank gives a full range of around 200 miles, usually going on to
reserve at about 160 miles. The offset, lockable, fuel cap is a neat idea if you
want to get a lot of fuel in without heaving the X) onto its centrestand but it
isn't in the best place to line up with cut outs in tank bag bases.
That big 8in searchlight on the front is adequate for 70-80mph riding at
night but it could do with a sharper cut-off and less spread. Luckily there's
plenty of reserve power in the X)'s 270W alternator if you want to mount a
couple of spots to give more penetration. Paintwork on the tank and frame looks
good but it's pretty thin and tends to start flaking off engine mounts and the
front of the metal front mudguard after a few thousand miles.
The mirrors give a useful rear view but tend to seize up on their ball
sockets at the top of the stems. There's little problem stopping the X), thanks
to twin lOin stainless discs up front and an 8in sis drum down back. There's not
a lot of feel at the handlebar lever, though, and emergency stops call for a
hefty squeeze. Again, it'd help if the lever was nearer the twistgrip instead of
being a finger-tip stretch. The discs work very well in the wet, too. No
problems with the Bridgestone boots on wet surfaces either.
We achieved a two-way average top speed of 115mph at MIRA, lying flat on the
tank, with a best of 117.3mph. Sitting up speeds were 109.2mph best and 106.5mph
mean so the X)'s capable of being a genuine ton up cruiser if necessary (or if
your neck and wrists can take it . . .). The YlCS-engined bike's time of 13.47
sees up the quarter-mile is exactly the same as the non-YICS version we tested
in December 1980 so the new technology makes the 650 no quicker though a little
more flexible and less thirsty.
The X)'s main rivals at the moment are Suzuki's two 650-four shafties, the
Katana and GT. Lumped together the Suzukis provide much the same package as the
XJ: shaft drive, plain, strong, two valves per cylinder motors an unfussy
chassis and equipment. But Suzuki went one step further than Yamaha and produced
both a sporty version and a general purpose/touring mount. The Katana may seem a
bit of an eyeful at first but it's as fast as the Yam, little thirstier and
handles much better. The CT is only a tad less impressive on speed and handling
and is definitely the pick of the two for two-up work, though it looks bulky and
sports an unfashionable amount of chrome.
Unfortunately the Yamaha loses out to both on price as well. The Suzukis are
between £100 and £140 cheaper on list price and the differential carries through
to discounts where X]s can be picked up for around £1750 and the Katanas for
£1650. The only slot the X)650 seems to fit into is a halfway house between the
two Suzukis where it scores over the GT on looks and the Katana on two-up
practicality. Which brings us back to the compromises which threaten to screw up
what should've been a good fast tourer.
Yamaha's sales and stocks situation is much better in Europe than it is in
the States and latest home sales charts for all manufacturers seem to show
there's plenty of life left in the over-500cc four cylinder market but there are
apparently no plans for another revise of the 650. If they're going to compete
against the best of the rest, maybe it's time there were some.

Source Bike 1983





{|  class="wikitable"
|- 
!Make Model
|Yamaha XJ 650 Seca
|- 
!Year
|1981
|- 
!Engine Type
|Four stroke, transverse four cylinder, DOHC, 2 valves per cylinder,
|- 
!Displacement
|653 cc / 39.8 cu-in
|- 
!Bore X Stroke
|63 х 52.4 mm
|- 
!Cooling System
|Air-cooled
|- 
!Compression
|9.2:1
|- 
!Induction
|4x 32mm Hitachi carburetors
|- 
!Ignition
|Transistorized
|- 
!Starting
|Electric
|- 
!Max Power
|71 hp / 51.8 kW @ 9400 rpm
|- 
!Max Torque
|57 Nm / 42 lb-ft @ 7500 rpm
|- 
!Clutch
|Wet Multiplate; 7 Steel 8 Friction
|- 
!Transmission
|5 Speed
|- 
!Final Drive
|Shaft
|- 
!Gear Ratio
|1st 2.187 (35/16) 2nd 1.500 (30/20) 3rd 1.153 (30/26) 4th 0.933 (28/30) 5th 0.812 (26/32)
|- 
!Frame
|Tubular steel dual cradle frame
|- 
!Front Suspension
|36mm Kayaba forks
|- 
!Front Wheel Travel
|142 mm / 5.5 in
|- 
!Rear Suspension
|Duel Kayaba shocks
|- 
!Rear Wheel Travel
|93 mm / 3.6 in
|- 
!Front Brakes
|2x 268mm disc 1 piston calipers
|- 
!Rear Brakes
|Drum
|- 
!Front Tire
|3.25-19
|- 
!Rear Tire
|120/90-18
|- 
!Wheelbase
|1445 mm / 56.8 in
|- 
!Seat Height
|780 mm / 30.7 in
|- 
!Ground Clearance
|145 mm / 5.7 in
|- 
!Dry Weight
|206 kg / 465 lbs
|- 
!Fuel Capacity
|19.5 Litres / 5.1 US gal
|- 
!Consumption Average
|48.6 mpg
|- 
!Standing ¼ Mile
|12.6 sec. / 171 km/h

|}

[[Category:Yamaha motorcycles]]