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Yamaha

Zero

   

Yamaha XS 850SG Special

 

   

 

Make Model

Yamaha XS 850SG Special

Year

1979

Engine

Air cooled, four stroke, transverse three cylinder, DOHC, 2 valves per cylinder.

Capacity

826
Bore x Stroke 71.5 x 68.6 mm
Compression Ratio 9.2:1

Induction

3x 34mm Hitachi

Ignition  /  Starting

Battery powered triggered  /  electric

Max Power

79 hp  57.7 kW @ 8500 rpm

Transmission  /  Drive

5 Speed  /  shaft

Front Suspension

Air assisted telescopic forks, 175mm wheel travel.

Rear Suspension

Swing arm 4-way adjustable damping, 99 wheel travel

Front Brakes

2x 267mm discs 1 piston caliper

Rear Brakes

Single 267mmdisc 1 piston caliper

Front Tyre

3.25-19

Rear Tyre

4.00-18
Seat Height 800 mm

 Wet-weight

258 kg

Fuel Capacity 

24 Litres

Braking 60 - 0 / 100 - 0

13.3 sec / 98.2 mph

Road Test 1979

WHEN THINKING ABOUT SPECIALS, DO you imagine yourself riding one down Main Street on Saturday night; and maybe rolling past Mel's Drive-In when the lunchtime crowd is there; or cruising smoothly on wheatfield-flanked two-lanes with an Exciting Companion at your back? Or does it bother you that Specials seem to place more emphasis on style than function? If you believe that these motorcycles are just razzle-dazzle corruptions of serious machines, then you're at odds with today's majority opinion .  and you may even be wrong. Some of the Specials are all flash; more often, now, they offer mechanical features that justify prices many riders have been paying for cosmetics alone.

Anyway, like them or not, the Specials can't be ignored. For one thing, they often out-sell standard models by margins large enough to have some Big Four executives considering making Specials their model-lineup mainstays, in which case the present standards would have to be sold as "specials." Another thing you should know is that the better examples of these drive-in cruisers also function surprisingly well as twisty-road scorchers, thanks to their stylish, super-fat rear tires and their refined, adjustable suspensions.

Yamaha demonstrated that style is not incompatible with function. The Yamaha 650 and 750 Specials were just styling exercises, but the tricked-out Eleven we tested a year ago proved to have been both styled and engineered. It was, and is, truly Special. As our report noted, the Eleven Special "can not only make the connection with the people who use the motorcycle as a stage and care deeply how they look when they're on it; the bike also appeals to those who are committed to performance and function."

Enter, here, Yamaha's new XS850SG, a bike that is in a quieter way a package much like its big four-cylinder brother. It, too, was designed after the sales appeal of styling had been firmly established, and is also a well-integrated design rather than merely being a standard model with an overlay of "appearance" options.

One indisputable benefit of the Specials' successes is that the Big Four's top management now listens more carefully when the marketing guys report what is being said by those who buy and ride motorcycles (whose opinions historically have been scorned as uninformed). And one message from the hinterlands was that the XS750 could use a little more engine displacement. "Right," the engineers replied, and Yamaha's XS triple got 3.5 millimeter oversize pistons for 1980, which gives the XS850 a total displacement of 826 cubic centimeters.

Myriad other changes were introduced with the bore increase. The larger bore required larger cylinder liners, which led to making a new cylinder block. The pistons have the same diameter as the Eleven's but are not the same parts. There has been no change in the triple's valve diameters, 36mm and 31mm for the intakes and exhausts, respectively, although the combustion chamber volumes were increased to keep the compression ratio at 9.2:1. The crankcase is the same casting, but its cylinder liner recesses are machined to take the larger sleeves. A wider primary drive chain, now 1 Vi inches instead of an inch, necessitated lengthening the crank's right-hand end slightly, and it needed heavier counterweights to balance the added mass of bigger pistons.

With a 10.6 percent increase in piston displacement and what Yamaha says is only a "minute" change in cam profiles, the new XS850 engine should deliver more power than the late-type XS750 triple. It apparently does not. The XS750E we tested in 1978 turned a 12.89-second, 103.80 mile-per-hour quarter mile; this XS850SG's best acceleration run was a 13.26-second, 101.46-mph effort wrung from it in the course of two-dozen tries. So Yamaha's 1980 triple, big pistons and all, is a little slower than the 78 XS750. Why?

Because this new Yamaha's performance, while certainly not dead, has been sorely nibbled by the EPA's ducks.

After years of using nothing but Mikuni carburetors, Yamaha has fitted the XS850 with a trio of constant-vacuum carbs made by Hitachi. You may associate the latter name with stereos and electronics, but Hitachi also produces carburetors—mostly for Japan's automobile industry. Having that background, Hitachi naturally has a lot of experience in meeting the EPA's emissions limits and for that reason the firm was invited to supply the XS850's carburetors. Besides, as one Yamaha representative confided, competition would make Mikuni work harder.

In any case, the 1980 triple does have Hitachi carburetors, which closely resemble the Mikunis they replace: they have 34mm throats, butterfly-type throttle valves and vacuum-controlled slides. The biggest difference is that the Hitachi carburetors provide a clean, no-lurch throttle response on the road but perform poorly at the drag strip; the Mikunis, of course, gave approximately opposite results. In normal riding the Hitachi carburetors were lean, but clean. At the drag strip they put a severe hitch in the XS850's performance, as the bike would cough and hesitate when full throttle was applied leaving the line. You'll occasionally get this lean-limit hesitation in street riding, but only when you're trying to get away from a standstill really fast; the old low-speed lurching is gone.

There's little doubt that these EPA mixers hurt our XS850's standing-start-quarter capabilities. On the other hand, they did wonders for the Yamaha's fuel economy. The average mileage we recorded was 42.6 miles per gallon, but that figure includes footpeg-scraping canyon rides that dragged fuel consumption down to barely more than 30 mpg. Brisk but steady highway cruising brought the mileage up to a miserly 54 mpg, and at that rate a touring rider could cover 200 miles before switching to the 0.8-gallon reserve supply. Nor will the touring rider have to worry about the quality of the fuel that goes in the tank: the XS850 ran fine, without perceptible signs of displeasure, on high-lead, low-lead and no-lead.

Air does not get to the XS850's ultra-lean carburetors without a fight. It must swirl its way through an EPA-sponsored equivalent of a funhouse mirror-maze, making two about-face turns on the way and then dodging around crankcase-fumes paraphernalia to get into the carb throats. Four-stroke motorcycle engines began to rebreath their crankcase vapors back in '73, and the fume-return system on the XS850 shows a determination that no wisp shall be allowed to escape into the atmosphere. Blow-by is routed from the crankcase into a separator chamber above the transmission, which is there to trap oil droplets, and then through a hose to the airbox where a complex of lines takes it to plastic nozzles that are jammed in front of the carburetor's intake bells.

If the EPA is responsible for the XS850's lean carburetion and tortuous air-intake system, neither of which may be said to help performance, it may not be blamed for what probably is a real cork in the triple's exhaust plumbing. The law, which reflects in this instance the reasonable and heartfelt wishes of all Americans not already deafened by truck traffic, says that motorcycles shall be effectively muffled. But current fashion in motorcycling dictates that mufflers shall be small, and the only way to make a small muffler effective is to fill it with restrictive baffles. The XS850 Special's mufflers are small, 100mm shorter than those on the XS750SF (which were appreciably shorter than the XS750 standard's), and even though they are linked by a cross-over tube for exhaust-pulse sharing they probably do comprise an impediment to exhaust out-flow. We'll know for sure if the standard XS850 has longer mufflers and is faster.

Measures have been taken to improve the durability of the triple's clutch. It basically is the same unit, but the friction plates have been narrowed and made 0.2mm thinner; and the all-metal driven plates are 0.4mm thicker. One result of the changes is that more of the driven plates' surfaces are exposed to oil splashing around inside the clutch, for better cooling. And the added thickness gives them better resistance to warping if they do get hot. The clutch in our test bike was a bit grabby, but to survive all those drag-strip runs it also had to be just about bullet-proof.

Two other changes have been made in the triple's drivetrain. Yamaha apparently has decided that total protection of the transmission from shock loadings is less important than relieving customers' un-happiness over drivetrain lash, because the triple's BMW-esque cam-type drive cushion has been replaced with a solid shaft. The rubber-loaded clutch-hub cushion has been retained, and certainly should be sufficient to protect the bike's rather elaborate shaft-drive system.

The second change in the drive is the new set of transfer gears between the transmission and the right-angle output bevels. The original XS750D's transfer gears gave it an overall top-gear drive ratio of 5.20:1. Another set of transfer gears moved the XS750E's top-gear ratio to a tighter 5.71:1 and that did as much for its vastly improved performance as the numerous engine modifications introduced in 1978. Now we have the XS850SG, and yet a third set of gears, which give a top-gear ratio of 5.35:1.

The standard XS850 is scheduled to have slightly lower (5.53:1) gearing than the Special, to suit its more ordinary 4.00-18 rear tire. Our XS850's front tire was a 3.25 H 19, the same size as before; the new Special's rear tire is a short, fat 130/ 90-16 Bridgestone. This shorter tire turns more revs than the 4.00-18 at any given speed and would have the engine doing likewise except for the taller gearing. With the transfer ratio change it's almost a stand-off: the XS750E needed 4520 engine revs to do 60 mph in top gear; for the XS850SG the figure is 4446-an insignificant difference. There is an important advance in the tires now used. They are tubeless.

Yamaha's styling department was no less busy than engineering when the XS850 Special was being formed, and both were getting some of their marching orders from marketing. For instance, marketing told styling that American motorcyclists think oil coolers look neat; styling told engineering; and the engineers designed the hardware for a factory-installed oil cooler, which is mounted across the frame's forward downtubes just below the steering head gussets. Other styling touches include: a step-seat with a more pronounced step than the XS750 Special's; a square-section solid aluminum grab-bar behind the seat instead of the usual chromed tube; a rounded, organic-look fuel tank; black-on-black lettering on the tank and side panels; candied coal-pile metallic black paint; and long, angled slots in the brake discs which may not do anything but look more trick than the usual round holes. The XS850's big, rectangular side reflectors may not please your eye or gladden your heart but Yamaha says they are what was needed to keep the DOT happy.

Styling has made the new Special's seat look a trifle thin in the area above the bike's side covers. It's an illusion. The forward part of the seat may appear to be cut lower than most, but its unladen height is 31.5 inches and that's only 0.4-inch under the original XS750's. There's plenty of padding beneath that quilted-look vinyl cover, and it's padding of the right sort. While soft (too soft for the confirmed, K. Roberts-style canyon racer), it does not squish down to nothingness after long hours of use and leave you effectively sitting on the plastic seat pan.

The only thing that's seriously wrong with the Special's step-seat is its step, which keeps you shoved forward even when you might prefer to slide back. This seat and the pulled-back handlebar insist that you adopt a bolt-upright seating position, and while that is fine when you're tootling along city streets trying to digest the hamburger and fries you downed at Mel's, it can get to be mighty uncomfortable at speeds above 50 mph. When the rush of air is strong enough to push your torso back you have to lean into it, but the Special won't let you do that unless you crane your neck forward and pull your arms back—an attitude that makes you look like an anxious turtle. The alternative is to let the breeze push you back into a straight-armed slouch, which may give you that Easy Rider feeling for a minute or two but soon puts a crick in your back and causes near-terminal wrist-cramp.

A flatter, straighter handlebar would help the XS850 Special's handling, even in Mel's parking lot, where you could stab yourself in the midsection with a handlebar grip trying to make a full-lock turn. But it cannot be said that the existing handlebar, however unhandy it often is, seriously affects the Special's stability or willingness to hustle around corners. The bike's suspension is too good for that, and it's adjustable, which means that if you don't care for what it's doing you can make it do something else.

Someday all but the cheapest motorcycles will have air forks and rear shocks with adjustable damping; the XS850 Special has them now. There is an air fitting under a rubber plug in the top of each fork tube, and you can make the front suspension stiffer or softer by raising or lowering the fork's internal air pressure. At least, that's the theory. Actually, it's very difficult to make fine pressure adjustments, as the volume inside the fork tube is so small that just checking the pressure will drop it a couple of pounds. Also, the position of the air stem is such that it can't be reached with some air nozzles. Still, with enough tries you'll be able to get the pressure where you like it, and that's a big improvement over no adjustment at all. Last year the XS750s used physical spring preload devices to alter their forks' stiffness.

The rear suspension units are easily adjusted. There are the usual five-notch camming rings for spring preload settings, and a small knurled knob at the top of each shock for dialing in the four rebound damping adjustments. The Special's fancy grab rail will keep you from getting at the rebound knob with your fingers, but any pointed object (i.e., a small screwdriver) will do the job.

Yamaha recommends a fork pressure of six pounds per square inch as an average, and advises that zero to a maximum of 36 psi will work. We pressurized our test bike's fork to over 36 psi without blowing the fork seals—through accident more than intent—and found that too much air made the ride unbearably stiff. Oddly enough, the ride was also adversely affected when the fork was completely depressurized: it was too soft, and the Special's front end developed a nod, which turned into a kneel when the front brake was applied.

With just a little air pressure in its fork (no more than 10 psi) and the rear shock damping at the softest setting, the Special delivered a positively luxurious ride. Yamaha banished stiction from the triple's fork long ago, the rear suspension's springs are light enough to yield readily for bumps, and the bike is a genuine floater when that's what you want. Unfortunately, the full-soft settings do let the bike wallow in corners and hobby-horse when it's traversing pavement heaves, pot-holes and the larger expansion joints. Our test riders found what they consider a good ride/handling compromise with the fork pressure at 15 psi, rebound damping at three-quarters hard, and the rear spring preload cranked up halfway. If you want to move the XS850's suspension into its best mountain-road mode, go full-hard on everything. This Yamaha is not blessed with an abundance of cornering clearance, but stiffening the suspension will let you make best use of what it has, and it minimizes both rear-end torque reaction and braking nose-dive. The dive-resistance is important: you'd expect the Yamaha's three discs and hydraulic calipers to give it plenty of stopping power, and they do.

Performance on the road is a little better than the drag-strip numbers indicate. The triple is a long way from being the horsepower champion of its displacement class, but it responds well to throttle at lowish revs (better than the XS750, we think, though these things are hard to quantify) and the passing power it provides is, well, passable. Still, if a real charge past a string of cars seemed appropriate, as indicated by the nearness of oncoming traffic, you'd want to downshift.

Yamaha has reworked the triple's engine mounts, and the new XS850 is smoother than most of the earlier models. There is no great amount of engine vibration at any speed, but our test bike settled into an especially smooth phase at 4600 rpm, which is about 62 mph in fifth gear. Yes, this is in excess of the legal double-nickle; it also is the speed at which most riders travel when not under direct observation by minions of the law.

Undoubtedly, part of the XS850's apparent smoothness is due to the vibration-isolating properties of its soft seat and rubber-mounted handlebar. We have to wonder if the softening influence of the bar mounts would be necessary with a less stylish collection of bends between the fork crown and the grips. The sheer length of tubing in a handlebar tends to amplify vibration, and a shorter, straighter bar might not need such an elastic connection with the fork. We certainly could do without the rubberized feel the soft handlebar mounts introduce into the steering. You won't notice the "give" when riding conservatively; it's unmistakably there when you add some sudden to your riding tactics. The XS850SG has a curb weight of 564 pounds, and you don't whack it smartly through a bunch of S-bends without using plenty of handlebar leverage. That's when you'll wish there was more feel of the rubber against the road and less of the elastic mountings.

Cycle's road test report on the XS750E compared its headlight and horn unfavorably with the BMW's quartz lamp and blaring hooter. Somebody at Yamaha was paying attention. The XS850 Special has a quartz-iodine headlight that does a truly satisfying job of brightening midnight; it also has dual-tone horns loud enough to reach the typical driver's deeply submerged consciousness. As before, the Yamaha has an automatic switch that shifts the headlight from low to high beam if the low-beam filament fails, and vice versa; and the bike has Yamaha's self-cancelling turn-indicators, which still are The Best.

The XS850 has a kickstarter, but that surely is an observance of tradition more than need. A new 280-watt alternator is provided to keep the Special's 14 amp-hour battery charged, and as long as the juice is there the electric starter will whirl the engine into action. If the battery is low, you probably won't be able to kick start the triple easily because: A) the kickstart drive is virtually an overdrive and the resistance of cold oil would have you jumping on it with both feet to turn the engine; and, B) the drive's ratchet doesn't engage until the lever is shoved down almost horizontal, allowing only about 45 degrees of well-muscled starter shaft rotation. We think Yamaha should get rid of the kickstarter, which would cut weight from the bike and put back a few dollars in the buyer's pocket. Anyway, when was the last time you saw a Cadillac with a crank in its nose?

A few of the Special's small touches deserve mention: Yamaha has wisely placed the fuel tank's filler cap to the right of center, so the tank can be filled to capacity even when the bike is leaned over on its sidestand. This is not a silent warning that you'll risk rupture if you try to haul the Special up on its centerstand. Actually, the stand is exceptionally easy to use, and that's partly because Yamaha made a hinged mounting for the Special's rear fender. So the centerstand does not have to hoist the whole back of the motorcycle a foot in the air just to allow removal of the rear wheel; it's a two-inch lift, tops, and accomplished with leverage instead of muscle.

Should you follow the maintenance schedule recommended for the XS850, you'll become well acquainted with your Yamaha dealer's service people. You can replace the triple's plugs yourself, but the valve clearances are set—at 5000-mile intervals—with selected-fit shim caps and that's a task for a mechanic with special tools and a basket of parts. Most other maintenance chores also have a 5000-mile spacing, and the owner's manual says that all but those involving the squirting or pouring of oil should be left to a dealer. But not even Yamaha's dealers are allowed to fiddle with the transistorized ignition's timing: the trigger-windings stator is riveted in place inside the left crankcase cover.

Yamaha's XS850 Special is, in most respects, an excellent motorcycle. If it is not terrifically fast, then it definitely is fast enough, and it's smooth, good-handling and has powerful brakes and most of the comforts of home. However, the Special's seat is too restrictive to be broadly useful and its handlebar is, in functional terms, an abomination. These features are functional concessions to style; as time and mileage accumulate, we would judge that Special owners will find the bar and seat less and less appealing. There's no denying that the 850 Special has showroom pizzazz, and people like what they like, so that point is beyond argument.

Source Cycle 1979 

 

 

 

NOTE: Any correction or more information on these motorcycles will kindly be appreciated, Some country's motorcycle specifications can be different to motorcyclespecs.co.za. Confirm with your motorcycle dealer before ordering any parts or spares. Any objections to articles or photos placed on motorcyclespecs.co.za will be removed upon request.  

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