What's New For Eighty-Two Yamaha
WHAT'S NEW FOR EIGHTY-TWO YAMAHA
A 650 Turbo, a 550 V-Twin, New 400s, More Suspension for YZs, Two Carbs for One Cylinder and That's Only Half of It.
Some of the new models were expected at the 1982 Yamaha show, but at least as many weren't. It's understandable when old models like the XS400 get replaced by with new XS400s with the latest in dual overhead camshafts and counterbalancers. And the XT550 four-stroke dual purpose bike has been long awaited as a replacement for the XT500. But then there's the Turbo Seca 650.
Yamaha's first production turbo looks to be a direct competitor to Honda's CX500 Turbo. It comes equipped with a stylish, sporting, full fairing and looks appropri ately futuristic. It's also based on an exist ing engine that has been treated to all the required changes to make a turbo work properly. Beginning with an inline Four, Yamaha had a much easier time with their project bike because the exhaust pulses are much more even than they are on the CX500 Twin. That didn’t stop Yamaha from developing a new type of exhaust that evens out the exhaust pulses of the XJ650 motor on their way to the 39mm Mitsubishi turbocharger.
Not being troubled by two cylinders Yamaha didn’t need to develop the electronic fuel injection of the Honda. Instead, there is a normal row of CV carbs, modified so they are pressurized under boost. That gets to another Yamaha difference. The 650 turbo starts out with a larger motor so it doesn’t need as much boost to develop staggering horsepower. Yamaha has set the wastegate and the pop-off valve at 7 psi boost.
It may sound as though the Turbo Seca is less developed than Honda’s turbo. Not so. It just starts out with a number of advantages that mean Yamaha doesn’t need to resort to the same techniques used by Honda. Much of the additional work done by the Yamaha engineers is internal strengthening of the engine and transmission. The oil pump volume is increased, £he crankshaft mainbearing journals are cross-drilled for better lubrication, the connecting rods are drilled so oil splashes inside the pistons for piston cooling and the piston crowns are 30 percent thicker than the standard 650 pistons to endure the added combustion pressure. Compression ratio is only slightly reduced so throttle response off boost isn’t affected.
The clutch and transmission are beefed up with 750 Seca parts to handle increased torque. A small oil cooler is fitted, i'he ignition is electronic, naturally, but it incorporates an electronic advance and a knock sensor. The knock sensor, fitted at the front of the engine on the cam chain housing, detects engine vibrations that are Caused by pre-ignition and automatically retards the ignition until the pre-ignition is eliminated. This knock sensor is especially useful on an engine like the Turbo Seca which will have high compression pressures at low engine speeds due to the extremely small turbo and the relatively high compression ratio.
Exhaust gasses are transmitted from the exhaust ports to the turbo by special stainless steel exhaust pipes, paired in a collector. Exhaust that runs through the ^urbo exits the lefthand muffler, while exhaust that is relieved by the wastegate ifcins out the righthand muffler. Not all the engine’s intake is run through the turbo compressor. When there’s no boost, the air runs through reed valves in the surge tank and bypasses the turbo.
Most of the Turbo Seca mechanical pieces are from the normal XJ650 Yamaha. That means a bore and stroke of 63 x 52.4mm, shaft drive, conventional twin shock rear suspension with adjustable damping, and normal air assisted tele> scopic forks in front, without the anti-dive brakes of the 750 Seca. The Turbo does get the new straight-spoke wheels and lightweight hubs found on several other new sporting Yamahas this year.
Even more unexpected than the Turbo Seca is the Vision, a 552cc liquid cooled VTwin. This is a large displacement version of a 400cc V-Twin sold in Japan, and it’s quite unlike anything else available, including Yamaha’s larger V-Twins or the Honda CX500.
To fit this into the Yamaha family, understand that Yamaha claims the Vision is faster than the 550 Seca, already a tremendously powerful 550. But the Twin is heavier than the Four by about 20 lb. What it is, is different. The engine is positioned in the single-shock bolt-together tube frame much as the Virago engine fits in Yamaha’s first flat tracker frame. And it’s the same sort of tubes-beside-the-engine frame.
The simplest description of the Vision engine is that it’s a slice off the Cosworth block. That’s also the description of the Hesketh V-Twin, but both of them are copying a successful racing engine. On the Vision it’s a highly oversquare design, 80 x 55mm. There are dual overhead cams, operating four valves per cylinder through inverted bucket followers with shim-type adjustments. Link plate chains operate the cams, one on each side of the engine as the Virago and 920 engines have. Unlike the big V-Twins, the 70° V-Twin Vision uses a gear-driven counterbalancer shaft at the front of the engine to reduce vibration.
Redline on the Vision is 9500 rpm, high for a Twin but comparable to the CX500 Honda. In order for this engine to develop more power than the Seca 550, though, it must breathe better because the engine doesn’t spin as fast. And that’s the secret of the power. Considerable work was done on the intake and exhaust tracts to improve volumetric efficiency. To take advantage of the clean, straight intake ports the engine is fitted with dual downdraft carburetors, another technique borrowed from automotive design. These aren’t CV or slide throttle carbs, but normal butterfly-controlled carburetors with accelerator pumps. Venturi size is 34mm on each carb.
Between the intake tubes is a connecting tube, part of what Yamaha calls the Yamaha Induction Control System. Like the YICS systems on the Secas and Maxims, the connecting tube adds to the swirl of incoming mixtures and increases efficiency at low speeds.
Beside the carbs is the fuel pump. It’s required because the angular and bulbous gas tank extends below the carb float bowls. On the righthand side of the engine is the waterpump, connected to the engine with steel tubes and the radiator with shrouded hoses. The sealed radiator is mounted in front of the engine, beneath the steering head.
To make room for the radiator and unusual gas tank the fork legs are offset a greater distance from the steering stem by the triple clamps. This would ordinarily reduce trail too much, so the axle is not mounted at the bottom of the fork legs or in front of the fork legs, but behind the fork legs. These are probably the first trailing axle forks since the Hatta forks found on Kawasaki dirt bikes a dozen years ago.
A five-speed transmission connects the engine to the shaft drive. The swing arm is a typical Yamaha monoshock design, with the small shock and spring located under the seat. Spring preload is adjustable to five positions. There is no air assist or damping adjustment on the single shock and there are no air caps on the forks.
Styling touches on the Vision range from the lightweight straight-spoke cast wheels to the molded-in taillight behind the soft seat. In between there’s the gas tank that shares some angles with a TZ roadracer, but most of its looks are like nothing else. The instruments are housed in a rectangular pod that grows out of the steering head, behind the rectangular headlight. Handlebars are adjustable in two ways, as are most of the Yamaha handlebars on new models. They appear much like the CBX I-beam handlebars and can be adjusted fore and aft where they pivot at the top of the fork tubes, but the ends of the handlebars can also be adjusted up and down.
Slightly tamer styling in the same design is found on the Seca 400, one of two new parallel Twins. Both the Seca 400 and Maxim 400 are offered with the new engine and chassis, in addition to a carryover model of the old sohe XS400. The new engine shares virtually no parts with the old engine. It’s a thoroughly modern dohe design with gear-driven counterbalancer shaft at the front of the engine and the alternator mounted behind the cylinders to keep the engine amazingly narrow.
Bore and stroke are 69 x 53.4mm for 399cc, now the smallest in the small street Twin category with the Honda and Suzuki at 450cc and the Kawasaki at 440cc. Like the Honda, the new 400 Yamaha uses the engine as a stressed member of the frame. From there, it’s all new, with a single shock being fitted to the monoshock rear suspension. Cornering clearance should be exceptional with the tiny engine. Even the clutch has been made larger in diameter to reduce its width. Claimed dry weight is 374 lb., there’s a six-speed transmission and only an electric starter is fitted.
The new lightweight wheels are used, along with a single front disc brake and rear drum brake. The Maxim 400 gets wire spoke wheels and noticeably different styling from the Seca.
Secas are offered in more sizes than ever before. There’s a 650 Seca besides the turbo. It has probably the cleanest styling of all the Secas, with a sleek gas tank, round headlight, small tailpiece and black-painted motor. It is the same basic bike as the Maxim 650 available for the past two years, but with a flat seat, sporting styling and lower, narrower handlebars. The rear tire is now an 18 in., though there’s still shaft drive. The 650 Seca doesn’t get the lightweight front wheel and superlight disc brake found on the 650 Turbo or the other new Secas, but it has the Seca 650’s narrow, powerful motor.
The larger Seca 750 gets a partner, the Maxim 750. Based on the mechanical components of the 750 Seca, the Maxim gets the normal specialized styling of the other Maxims, plus a number of new features. To go with the adjustable handlebars there are adjustable footpegs. These can be moved forward or backward through a range of two inches. The combination should go a long way to satisfy the demands of many different riders. It's worth noting that the stepped seat of the Maxim 750 is not as extreme in shape as previous high-style bikes and appears to have more padding for the rider despite a relatively low seat height. New features on the Maxim 750 include the interconnected air-assist shocks at the rear and the interconnected air pressure on the forks. Fork rebound damping is easily adjustable by turning knobs at the top of the fork legs.
Another Yamaha acronym is appearing on the Maxim 750. This one is CYCOM, though what the letters stand for is a mystery. It goes one step beyond the computerized monitoring system found on last year’s Seca 750. On that system liquid crystal displays warned the rider if the sidestand was down, the battery, oil, brake fluid or fuel were low, or the headlight or taillight were out. In addition, the Maxim 750 has a digital speedometer and tachometer. Switches on the instrument pod allow the speedometer to be switched between miles per hour and kilometers per hour. The tachometer can also be switched to register a 2000 rpm scale for exact idle settings.
A special X-l touring package consisting of fairing, saddlebags and top box will be offered for the 750 Seca. The equipment is smaller than most full-size touring accessories and fits on the Seca as unobtrusively as such equipment can.
There are no 850 Triples or 500 Single for 1982 and there’s only one 1100. Yamaha is reacting strongly to sales reports that indicate big bikes aren’t selling well. The only 1 100 is the Maxim 1100, a bike that shares the air adjustable suspension ■of the Maxim 750, but doesn’t have the adjustable footpegs and ornate instruments of the smaller Maxim. It even has a round headlight. No touring equipment was shown for the 1100. The Maxim 1100 retains the integrated braking system first seen on last year’s Midnight Special 1 100, and has the YICS intake system added to the engine.
Yamaha’s larger V-Twin motorcycles continue unchanged for the most part, with the addition of a Virago 920. The 920 Virago is a mix of XV920 and 750 Virago, with the large motor, but coupled with shaft drive. New middle gears provide lower gearing than the XV920 for better top gear acceleration. The 920 Virago shares the CYCOM electronic instrument panel with the 750 Maxim, and it gets a rectangular headlight replacing the giant 8 in. round headlight of the XV920. A new black and gray paint scheme makes the ^XV920 look more tasteful for 1982.
Two old standbys continue in the Yamaha lineup, but in revised styling. The XS650 and XS400 that have been around for more than a decade are now updated to be called Heritage Specials. These are very basic bikes, lots of black paint, including on the fenders. There are wire spoke wheels, even a drum brake on the front of the XS400 Heritage Special. Both bikes retain both electric and kick starting. A little careful trimming of the cylinder fins on the XC650 makes the engine > appear different than it’s looked before, but mechanically it’s the same old sohc vertical Twin that’s powered the 650 for years.
Yamaha has had single shock racing bikes longer than anyone. And the original Monoshock design was good enough to stay basically unchanged from 1973 through 1981. But the other companies have been burning the midnight oil the last couple of years and all of them have designed single shock motocross machines.
So, 1982 marks the first year Yamaha has made a radical change to the Monoshock system. The shock body is still under the seat and tank, the rear lower than the front, although the aluminum shock is again completely new. The biggest changes to the system are centered around the swing arm. The new boxed aluminum arm lacks the trianguation of past Monos, looking more like the other single shock arms. The big change is at the front of the arm where the shock bolts to a pair of aluminum levers that make the Monoshock design progressive. Past Monos have resorted to dual springs or tapered wire springs for progression. All of the levers associated with the new system are aluminum and most of the pivots have grease fittings for ease of maintenance. Yamaha has had many names for the prototypes we’ve watched develop on the factory works bikes but named the final design New Monocross.
The aluminum shock is completely new once again, including the spring. Damping adjustments have been updated to include 15 compression damping choices in addition to 30 rebound. Rebound is adjusted at the rear of the shock as before, compression adjustments aren’t quite as easy, requiring the use of a flat blade screwdriver to reach the adjustment knob that’s buried between the right side of the tank and frame backbone.
Front suspension is also new on the 250 and 490 YZs. Gone are the cast lower legs, replaced by legs made from extruded aluminum tubes with welded-on lower caps and pressed on axle bosses. Stanchion tubes remain 43mm in diameter and travel is the same at 11.8 in. Yamaha spokesmen knew little about the new forks and couldn’t answer questions about damping rods and other internals.
Complementing the new suspension systems and new frames are new engines. The open bike has increased displacement by a larger bore, and transmission speeds have been reduced to four from five. Four gears instead of five, in the same cavity, means size and strength are increased, and four speeds are all that’re necessary in an open bike used strictly for motocross. Yamaha’s YEIS intake system is also standard on the open motocrosser for ’82.
Big news for the YZ250J is watercooling and variable exhaust port. The seemingly overly-complex watercooling system from last year’s YZ125 is copied on the 250. Bore and stroke and five-speed transmission remain the same. The watercooling is a good touch but probably more important is the new power valve that changes the height of the exhaust port in a direct relation to engine rpm. When revs are low, the exhaust port is low so good torque can be produced. When revs rise, so does the height of the exhaust port, letting the engine spin faster. The valve is positioned across the top of the exhaust port and shaped like a cylinder with a U cut out of its center. The U rotates to change the port height. Rotation is controlled by a linkage system that goes from one end of the cylinder valve to a centrifugal governor mechanism on the end of the crankshaft. This power valve system is standard on the YZ125 as well and may prove to be the best thing to happen to the two-stroke engine since the reed valve.
Styling is also new on the YZs. The seat/tank area is the most notable difference; the seat extends up the tank almost to the gas cap. The tank is shaped so the seat fits down into it and a hook and loop system keep the two together. The idea is to let the rider slide as far forward as he wishes. A new wide front fender, larger rear and square numberplates round out the package.
Yamaha has two sizes of minis for the smaller racers, the 60 and an 80. The two are sized differently to accommodate different ages and sizes of kids. Both have monoshock rear suspensions but neither gets the new link monocross system. Both get the new seat-to-the-gas-cap treatment and the 80 is watercooled and fitted with a YEIS canister. The 80 also has a new frame and front fender.
The 100 class has been mostly ignored or given little attention in the past. Several playbike 100s have been available, but most needed lots of changes before being competitive. Yamaha is trying to muster more interest in the 100 class this year. They have announced a dynamite YZ100 that incorporates the new monocross link rear suspension, new frame, 18 in. rear and 21 in. front wheels, leading axle front forks, six-speed reed induction engine and big YZ styling.
Yamaha’s IT line was very competitive last year and Yamaha has chosen to radically change only the 175 for ’82. The open bike has a YEIS canister as its only obvious change besides the bright blue and yellow color. The 250 has only the color change. The 175 class is the big class and it’s usually the most competitive. So, the 175 IT is mostly new. It gets the new Monocross linkage rear suspension, new frame, new seat and tank, new square number plates, tubular engine guards and a wider power band.
Between the dirt and street bikes there’s the XT550. This is the biggest Yamaha dual purpose bike, and it’s entirely new for 1982. The engine is the biggest news. It’s a sohc four-stroke, still, but now with four valves and a gear-driven counterbalancer shaft for smoothness, and it’s part of a new frame that uses the engine for a stressed member, lowering the frame. The drysump engine is protected by a flat bash plate that substitutes for large frame tubes. Oil for the engine is carried in the new frame. At the back of the frame is a single shock suspension, the kind Yamaha has been putting on its motocrossers for some time.
What makes the XT550 particularly unusual is the carburetion. To feed the two intake valves are two carburetors. Actually there are two carburetor bores with one float bowl, so what it amounts to is a two-stage, two-barrel carburetor. Twist the throttle and a small 26mm slide throttle carburetor opens up, supplying its mixture to the lefthand intake valve. When the throttle is more than half way open, mechanical linkage between the two venturis opens the butterfly valve of the second barrel, but this one’s a vacuum-operated CV carburetor, so it begins opening the slide when air starts flowing through it. This second barrel only feeds the righthand side valve. This is Yamaha’s way of getting good throttle response at low speeds that requires a small carburetor, and providing plenty of breathing for high power when the throttle is cranked wide open. In addition, when only the small carb is working, the incoming mixture is only running through one valve, causing a swirling mixture for better combustion.
There is no TT550, and no SR550, Yamaha claiming there will be a pure offroad version later. The XT and TT250 remain, plus there’s a new XT200, a smaller version of the XT250 to replace the DT175.
Yamaha’s old two-stroke DT dual purpose bikes have been relegated to the bottom of the heap, only being sold in 80 and lOOcc models. A new XT 125 replaces the DTI 25 with a four-stroke sohc engine. Like the larger XT, it uses a counterbalancer shaft, stressed engine frame, single shock rear suspension, 21 in. front tire, and has electronic ignition and primary kick starting. The 125 comes with a sixspeed transmission.
