Cycle News - Archive Issues - 2000's

Motor Engine performance has always been a big issue when it comes to building a competitive 12S, and it's probably even more of an issue now than ever before. Not only did 12Ss have to battle for horsepower supremacy among themselves, they now have to contend with the fourstrokes, which is no easy task when you consider that the 12Ss are giving away twice as many cubic centimeters to the hugely technologically advanced 2SOcc thumpers these days. Is that fair?Well, that's a debate for another time. But for now , 12Ss have to race against the larger four-strokes and. of course,among themselves - engineperformance is even more critical today than ever before. This could explain why all of the 12Ss in this shootout have taken on numerous engine updates for '04 - even the KXI2S, wh ich won our shoctout last year. There is just no resting on your laurels these days. Kawasaki pretty much redesigned the KX's engine in search of more low-end and midrange power. The cylinder has been reshaped, compression has been increased, the piston and ring are all-new, the KIPS power-valve has been modified , the intake reed-valve system has been thoroughly gone over, the carburetor and air intake manifold have been tweaked, and the ignition has been revised. Even the exhaust pipe has been replaced to improve midrange and top-end performance. Yamaha wanted more midrange and overrev on its new YZ, so the cylinder, YPVS powervalve system, carburetor, exhaust pipe and ignition have all been modified . The yz has enjoyed a reputation for already having one of the best 12Scc two-stroke motors out there for many, many years, so the company is careful about what it does to its popular 12S. In recent years, KTM has been known for its incredibly powerful 12Scc motor in the SX, but because of this bike, we've learned that horsepower isn't necessarily everything, even in the 12Scc class. Many years ago, KTMcame out with the undisputed horsepower king of the 12Scc class, but unless your name was Grant Langston, you couldn't ride it to its potential too peaky, too hard to control, too much like a lightswitch , But ever since that bike, KTM has been smoothing out the SX's powerband, trying to make it easier to ride without sacrificing overall horsepower. This year, KTM made a lot of changes to the SX's motor to give it more torque and a better transition from nothing to everything. Suzuki made many refinements to its already potent engine. The goal was to improve midrange and high-end performance and make it more tractable, so the Suzuki techs basically redesigned the cylinder, installed a new flat-top piston, reworked the exhaust power-valve system, and le ngthened the connecting rod and increased crankshaft inertia. East Coast 12Scc SX Champion Branden Jesseman should be happy. Honda also made a lot of changes to its CR 12SR's engine . The bike has suffered a bit In the horsepower department lately, but a lot of testing has revealed that the bike has been suffering from a bad case of asthma - it just can't breathe. So, according to Honda, everything that has anything to do with air or air flow has been modified , such as the air intake boot, the airbox, the carburetor, the reed-valve intake system, the exhaust valves (which are now electronically operated), and the cylinder. You name it, it's been changed . But did it help? We can safely say that all of the bikes here in this shootout have outstanding motors. T here really isn't a dog in the bunch, not even the Honda's anymore. Unfortunately, it's still a tick off of the others. All of our tes ters agreed that the CR's motor is much improved over last year's but just doesn't produce that kind of adrenaline rush that the others do . This could be, however, because the Honda tracks so well exit ing the turns that it perhaps creates an illusion that it's not making as much power as the others. This isn't to say that there isn't a sweet spot in the CR's powerband, which there is, but it's a little hard to find. But once you do, hold on! Some of our testers felt that the CR might be better off with a six-speed transmission. It seems that the CRI2S has struggled in the motor department ever since it went from a sixspeed to a five-speed , At the other end of the spectrum is the KTM's motor. It's still the ho rsepowe r king and is far easier to control than ever be fore . Not only is the thing just plain fast, but it also has torq ue, which is pretty much unheard of fo r a 12S. This torquey and overall powerful motor rea lly be nefits the rider on the faster "outdoor"-type mo tocross tracks, where the KTM really works well. On tighter supercross-style tracks like at Starwest, however, some of our testers weren't quite as impressed, feeling that if you get below the KTM's torque curve in the supertight turns, the KTM is slow to respond and could use a bit more bottom-end grunt. Faster riders who could better keep up their momentum through the comers had no complaints. Plus, our more novice-skilled riders were less confident with their throttle control over the doubles on the KTM than the others. The Suzuki, Kawasaki and Yamaha motors aren't all that much different fro m one another. They're all really, really good and plenty powerful. Okay, maybe not as powerful as the KTM's motor, but pretty darned close. Among the three, Suzuki's is perhaps the most pipey, or, in other words, exciting . It revs quickly and fee ls very lively; it just seems to want to say to you , "Let's go, let's go, let's go!" every time you hop on it. The Suzuki has a fairly broad powerband and is almost always ready to react when you open the throttle. The RM is pure excitement, but perhaps a little too excitingfor some, mainly novice-levelriders. This bike is serious. All of our testers had nothing but good things to say aIbout the Kawasaki's motor. "Grea t bottom-end ," "supe r controllable: ' and "excellent transition from midrange to top-end:' were just some of them. From our novice riders to our experts, the KX pleased them all, just like the Yamaha's motor did. But when it came time to choose which one was best, all of them pointed to the blue bike. "It [the Yamaha's motor] is just like the Kawasaki's but just a little bett er: ' said one of our testers, w ho perhaps best summed up the YZ's motor. "It just has the best bottom-end, the best midrange and revs out farther than any of them. It just wouldn't sign off." Also like the Kawasaki, the Yamaha's motor was not only potent but also very manageable for both the novice and expert rider, and the Yamaha's motor just worked well on a variety of tracks, from supertight supercross tracks to wide-open motocross tracks. HONDA: "Has its moments." "Revs to the moon but it needs something on Earth - more bottom-end." "Big improvement over last year's." "Hard to work on tighter tracks." "Whatever it may lack in sheer horsepower is made up for in tractability." KAWASAKI: "Great motor but just not quite the greatest motor." "Very predictable and user-frien dly fo r a 12S." "There's always power on tap." "Doesn't require a lot of clutch-work." KTM : "Feels like a small 2S0 - two-stroke, that is." "Very powerful but far more manageable than before." _______________..; www.cyclenew s.com "Pretty torquey for a 12S." "Ideal for outdoor motocross tracks, perhaps the best of the five." ''A little bit of a handful on tight tracks." SUZUKI: "Snappy and lively." "Revs quickly but just doesn't seem to pull as hard as the KX, yz or the SX." "The Suzuki seems to encourage you to ride it aggressively." "Despite the changes, the RM's engine does n't fee l much different than last year 's." YAMAH A "Robust ." "Wo rks well on a wide variety of tracks." "Th rottle response is instant." "Lo ts of power everywhere." "Doesn't get much better than this." CYCLE NEWS • JANUARY 21,2004 17

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