Cycle News - Archive Issues - 2000's

MotoGP Tech: The Games Begin use some of the space that allows hot air out of the radiator and therefore make the cooling a bit marginal. As a result, special fairings were required last year for the heat of Qatar. There have only been two motorcycle 'The first MotoGP tests of 200S immediI ately brought home the seriousness of Yamaha' s determination to give Valentino Rossi the best possible bike on which to retain their hard-won MotoGP World title. There are many ways to make a bike go qUicker without merely increasing the power. If you can achieve perfect handling, you can use more power in tricky situa- tions: A smaller frontal area will give a higher top speed, a better quality suspension will allow more grip. The new Yamaha is better in all these areas to the model that won the championship last year. These new pictures show Rossi's 200S M I with the fairing off, and they show a completely new motor and chassis using some really neat ideas. The sixspring slipper clutch is probably the only the only part unchanged on the whole motor. The completely new engine (see comparison picture of the old one) clearly shows the high-mounted clutch, which means the gearbox is completely vertical for the shortest possible engine block. You can see by the way the clutch is spaced back from the crankshaft that Yamaha still had to find room for the extra shaft it uses to allow it to run with reversed crank rota- tion. Because of the way that the backward rotating crank's gyroscopic effects change the handling, the Yamaha is a very agile, easy-turning bike. The new design has necessitated a very complex split in the crankcases, with the front half of the motor split at nearly 4S degrees to allow the revised shaft assemblies to be bolted into place. If you look carefully at the photos, you can also see that both sides of the engine show a water jacket. On last year's engine, you had a very obvious cam chain and gear assembty on the right-hand side. Obviously, you have to drive the cams somehow, but all conventional designs put the JOmm-wide gear or cam chain assembly in line with the cylinders - either at one end or in the middle and that makes an in-line four quite wide. The new chassis uses the same long front frame spars to connect the chassis to the crankcases that Yamaha fitted last year to get its bike to handle as Rossi wanted, with the spars allowed the steering head to flex more for better front-wheel grip at lean angles. The trouble is that the spars 8 engines that have driven their cams from the back of the cylinders: one that famed Italian bike designer Leno Tonti built back in 19S8, and the other from British designer Patrick Walker's prototype MC4 Maxsym twin (now in production as the Maxsym GPSoo/6oo). By putting the cam drive on the back of the engine (a very easy thing to do when you already have a highmounted shaft running along at the base of the cylinders), up to JOmm can be chopped off the width of the motor. This allows the chassis spars to be moved inward and the fairing to be narrower while still allowing for more hot air to be removed from the radiator. With the potential for a reduced frontal area, this is one modification that can trans- late immediately into increased top speed. Looking carefully at the cylinder head cover, you can see a small plate on the front of the cam cover. This seems to be part of the breather system used to reduce internal crankcase pressure. Last year's bike had this mechanism on the top of the gearbox. With pipes going around the cylinders to the exhaust pipes and that space now used by the cam drive, they had to put it somewhere else. You can see the small pipes that transfer the exhaust-pipe pressure fluctuations going into the exhausts right up at the cylinder head. This system is an old NASCAR idea and can gain several horsepower by making it easier for the pistons to come down from top dead center. Another change is the revised sump with all the oil now on the right-hand side of the engine. This has necessitated a new exhaust system design with all the pipes now being routed down the left-hand side of the bike. Two of the pipes now join into one very early in their length. The changes don't stop there. The picture of Rossi's bike with its fork in shows a new design of Ohlins fork: The gas reservoirs that previously lived alongside the fork tubes are now gone. For the last few years, Sachs FEBRUARy 2, 2005 • CYCLE NEWS and Ohllns have been perfecting a new, twintube, constant-volume shock absorber technology for cars that uses technology not dissimilar to that on a typical steering damper, With this technology, very low gas pressures are required and no gas reservoir is needed, giving very precise, easily adjustable damping. Noticeably, Colin Edwards' bike (shown here) has last year's TT 2S fork, while Rossi has got the very first version of the new technology on his. Suzuki used three bikes at the first test of the year - Kenny Roberts Jr. and John Hopkins on last year's power delivery were compromised to improve handling. Eskil Suter's involvement in the chassis design had paid off, but all that happened was that the deficiencies of the motor became more apparent. Yamaha's across-the-frame four is very different from the Kawasaki's. It has a revised firing sequence, a long bang rather than big bang, a crank that turns backward to reduce excess gyroscopic stability, and arguably the most important change - a shaft that can be used as a balancer. chassis with a new motor, and the same engine in a new chassis used by test rider Akayoshi. The bike had several new technical features and appears to have a different swingarm and shock-absorber layout - likely giving a full-floating suspension system like that used by both Honda and Ducati. A new exhaust system is also being used - getting the long, rear cylinder exhaust out of the way of the new shock position. Kawasaki also showed up with a few changes. Although a new motor is scheduled for the next test, Kawasaki had new fairings and seat and tank units for this test. last year's unit, with its trademark, small flip-top airbox, has clearly been redone with a new carbon-fiber one-piece unit sitting on top of a reinforced seat unit. The most likely reason for this was to give more strength to the airbox, allowing it to act as a resonant chamber and increasing horsepower at whatever parts of the power band the engine designer feels is needed. Kawasaki has a new engine on the way, and the current Kawasaki is the last of the "superbikes on steroids" designs. Last year, the motor was clearly the weak link, as pistons and rings failed and the internal engine design and Yamaha's unique long-bang crank design means it needs a balancer for the big primary forces, just like you would need for an old British twin. Balance shafts can sap power, but Yamaha is able to use the crankreversing shaft behind the cylinders for both purposes. Conventional firing sequence four· cylinder engines have a natural secondary vibration: It's a high-frequency vibration rather than the big primary vibes of an old British twin, but it can be very damaging at high revs. Last year, the Kawasaki was literally shaking itself apart. Kawasaki needed to sort out its motor problems - even if it doesn't make a long-bang engine - but it makes sense for Kawi to address both things at once. Kawasaki uses balancers in several of its street engines, but this will be the first in a race engine. To help the process, Kawasaki's garage had two notable new members, both of who were involved in Yamaha's M I project since its inception. They are ex-Yamaha chief engineer and MI project leader !chiro Yoda, and ex-Cagiva and Yamaha crew chief Fiorenzo Fanali. Both arrived in 5epang in Kermit green. After successfully hiring ex-Yamaha rider Shinya Nakano and his entire team last year, Kawasaki's effort is clearly going up a gear - and in a Yamaha direction. Neil Spafdlng

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