Cycle News - Archive Issues - 1990's

FIRST RIDE WTI'lm U~©[}{]8 @Q®[?01Ji) UNLIKE SUZUKI, HONDA /-lAS TRODDEN THE V-lWIN SPORT- 14 bike trail before - most notably with the eight-valve RS750 dirt-tracker which in RS850 road racing guise was enough of a Ducati-beater to allow Randy Renfrow to defeat the otto vaLIlOle 888 desmos and win the American BoIT title a little over half a decade ago. Thenl was some pressure on Honda back then to make a liquid-cooled street version of the 45-degree Vtwin dirt devil, but that was never a realistic option. Instead, they delivered the six-valve 650 Bros sports twin, which went on to become a cult bike in Japan, even if those of us in Europe only ever knew its bland commuter cousin, the Revere, based on the same 52-degree V-twin motor which many tuners in Japan punched out to BOOcc-plus with the aid of, er, Cagiva Elefant pistons. However, these projects had set the ball rolling, and now Honda ha (re-?)d.iscovered the sporting V-twir, with the coming to the marketplace of a project that's been a long time brewing: since 1986, in fact - the first time Honda R&D ,started looking at making a worldmodel V-twin sport bike. But it wasn't until five years ago that Honda began thinking seriously about the project, asking its American and European affiliates to research the • market and construct a pair of prototypes each, which ended up being built to rather different parameters. Honda America wanted a 90055 Ducati-type sportbike (and the U.S.-built prototype pictured with the VTR1000 shows how cobby that might have been), but the Europeans wanted a less hard-edged Paso/907-type all-rounder. The fact that, after each side went to bat with Honda's boss of product planning, Kiyoshi Nagashirna, 6,000 of the 10,000 VTRlooos scheduled for production in the bike's '97 debut year will go to Europe, against just 2,000 to the USA, underlines who won the argument after the go-ahead for the all-new VTR motor was given exactly three years ago. However, it's probable that the time lost in discussion allowed Suzuki to catch up and latch on to the same idea: Try to build a better Ducati at more affordable cost, to Japanese standards of quality control and reliability, incorporating the potential for customer or factory tuning to a variety of levels up to and induding superbike racing. The VTRl000F now entering production is the first step along a path of ongoing V-twin development, representing a separate strand from Honda's VFR/CBR fourcylinder design modules. Honda top management admits privately this is only the start. Just as Ducati's 900SS motor powers the Monster cruiser, Elefant trail, -Grand Canyon street rod and Sf2 sport touring spinoffs, so could there be several different versions of the VTR concept in the future, of which the VTRl000F represents just the kickoff. • So rather than the fuel-injected R-bike contender for superbike supremacy that many foretold (that'll come a year from now, together with a race kit for the carbureted F-bike: A prototype VTR racer has already been captured on film testing at Suzuka by Riders Oub magazine) the VTR1000F is instead a baseline model for real-world riding, aimed at the Ducati 900SS market in terms of price, offering the performance of the 916 Biposto, but wrapped up in an all-rounder package all its own. That performance comes in spite of the relatively humble 9.4:1 compression ratio and 48mm slanted flatslide CV-type Keihin carbs; these are nevertheless by some way the largest carburetors ever fitted to a Honda motorcycle - or probably anything else, for that matter. The 9O-degree V-twin engine does have the same 98 x 66mm bore and stroke as not only the Suzuki TLl000, but also Troy Corser's 1996 world champion Ducati 996, now homologated for the street in the guise of the 916 SPS launched alongside its Japanese imitators/rivals (you choose) at Cologne. Honda says these dimensions were arrived at as part of their objective to deliver "a strong, wide band of high-torque power, reaching all the way to a high-revving peak, yet with little or no annoying vibrations." Well, they would say that, wouldn't they? The 90- Ow ® Q@®©qJJ[p1( degree format with its perfect primary balance chose itself, if they wanted to avoid either the power-sapping balance shafts needed to iron ou t the vibes in a narrowangle V-twin, or the unproven reliability at high revs of offset crankpins to achieve the same effect. And the bore and stroke ratio? - well, the World Superbike points table says it all! However, where even Ducati's Massimo Bordi admits Honda has taken a step forward is in the design of the VTRl000's crankcase, which unlike its rival vee-90s is horizontally split, with the cylinders cast integrally with the upper half to provide a very stiff structure. This idea isn't new - the 6O-degree V-twin Harley VRlOOO Superbike has had it all through its drawn-out development cycle - but it is the first time this feature has made it to the street on a V-twin. The whole Honda engine is designed to be an integral, fully load-bearing part of the chassis, in turn reducing weight and bulk - hence the copious ribbing on all the castings for extra strength, especially around the chassis pickup points. In addition, the Honda takes a leaf out of Ducati's book by pivoting the composite extruded/east alloy swingarm in the crankcases - not only, says Despite being heavily ribbed for stiffness, the VTR's 90· degree V-twln'. dry weight Is comper1lble to a Ducatl'.. Honda R&D boss Takashi Shinozaki, for the indefinable difference in ,feel obtained, but to further underline the engine's role as a stressed chassis member, allowing the so-called "pivotless" twin-spar alloy frame to be lighter and more compact than otherwise, weighing just 15.4 pounds. The steering head and rear chassis section are both alloy castings, linked together by extrusions with dualbox internal stiffening. The rear casting provides a solid mounting point for the top end of the Showa rear shock with its Pro Link progressive linkage. Both the VTR's conventional cartridge-type 4~mm fork and the rear shock are only adjustable for preload and rebound damping, though - neither of them for compression. Remember this is the Stage One ground-zero model, on which cost is a factor. Back to the engine, which is the heart of the matter on the VTR, even more so than usual for Honda. There's a lot of nice stuff inside here which points the way ahead for future R&D. Like the lightweight, ultra-slipper threering pistons connected to the plain-bearing, single-pin crank by so-called "nutless" side-by-side rods, whose big-end bolts screw directly into the boss of the connecting rod without resorting to the usual locking nuts. This saves 40 grams per rod, all part of an overall weight-paring strategy which sees the VTR motor weigh in at 150 pounds dry (less carbs), compared to a 916 Ducati motor's 156 pounds, while claimed dry weight of the complete half-faired YTRl000F is 422 pounds. The DOHC four-valve cylinder heads "With direct chain-driven camshafts - no Rumi-type intermediate gears, like on the Suzuki - have the largest valves ever fitted on a Honda, 38riun inlets and 34mm exhausts operated by shimmed bucket rockers, and are rotated 180 degrees to each other. This design has the double benefit of keeping costs down by the use of identical eastings for the front and rear cylinders, and having the two carburetors facing each other other so 'that they can breathe through a common eight-liter airbox. Inherent to this design is the fact that there is a cam chain on either side of the engine, the front cylinder's on the left, the rear's on the right. The digital ignition incorporates throttle-position and engine-rpm sensors to electronically vary the advance curve, with a 10,300 rpm rev limiter - some way above the 9,OOO-rpm power peak at which a claimed 107 horsepower is produced - probably translating to about 92-94 bhp at the rear wheeL A six-speed gearbox with quite closely matched top five ratios and hefty 10-plate hydraulic clutch take care of pu tting this to the road, while the hefty peak torque of 70.9 foot-pounds in unrestricted 11 O-horsepower guise is delivered at 7,000 revs. Proof that Honda was aiming at a torquey, ridable engine package for this F-model comes in a comparison of the torque figures for the l00-horsepower versions of the Honda and Suzuki once the TLl000's horsepower advantage is wiped out. The French/German-market 100-horsepower models deliver 69.4 foot-pounds for the Honda, against 66.3 for the Suzuki: The VTR1000F is designed for everyday sports riding, rather than racer road. One of the nicest tricks on the VTR and a key factor in capitalizing on the inherent slim build of the V-twin motor is the cooling system. Instead of a single wide radiator spr~d acroSs the front of the engine, which fuels a vicious circle by directing hot air out the back onto the engine cylinders, in tum increasing cooling requirements, Honda has fitted twin, side-mounted radiators on the VTRlOOO, with just a tiny, twin-row oil cooler spread crossways between them. Not only does this greatly reduce the risk of stone damage or part-blockage by bugs, it also eliminates the radiator as a factor in determining engine location or wheelbase, since there's no restriction on front-wheel clearance due to fork deflec, tion under heavy braking. Following a principle first seen on the oval-piston NR500 GP racer; and the later Saxon Triumph's rear-mounted radiator, the VTR's twin sidemounted rads work thanks to the low-pressure zones created at speed by the air flowing across the external radiator ducts, which literally pulls the air through the rads from the higher-pressure pocket behind the front wheel, thus cooling them. The design of the fairing curvature is crucial to this, but there's a single fan on the inside of the right-hand radiator to blow air through it in heavy traffic or on a hot day. Stuff like the cooling system and crankcase design show Honda invested some original thought in penning the VTRl000F, rather than simply cloning a desmoquatlTo: They just had some, er, inspiration to fuel their ideas, wafting its way to Japan from 'Bologna, via the U.S. of A. But now Honda's engineers are surely working on Stage Two and beyond, the pace of its efforts undoubtedly stepped up in response to the appearance of the TLlooo Suzuki. Market forces will determine the commercial success of these two very different approaches to the large-capacity sport twin concept. But in the realm of absolute performance, the crucial question both Japanese marques have still to answer is a simple one: Can they succeed where Harley-Davidson and Aprilia have so far failed and deliver consistent Ducati-matching horsepower and ridability to a superbike race versiol;\ of their new V-twins, without a system of positive valve control which will allow them to go for more power at higher revs-? Marketing constraints prevent Honda from adopting Ducati's mechanical desmo package on a motorcycle and Shibazaki says in any case that "desmo is too complicated, and doesn't have such a nice throttle response or engine behavior under braking." Will we therefore see the VTR adopt the pneumatic valve control now commonplace on Formula One car engines, in order to duff up the Dukes? And, if not, will the VTRl000 be a Storm in a teacup, superbike-wise? Jury's out...

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