At the beginning of the 2001 race season, the only sound ringing through supercross stadiums more distinctively than the 12,000-rpm hum of Ernesto Fonseca's Yamaha YZ250F was the controversy surrounding its legitimacy in the class. A mere two years later, the little four-stroke's rumbling voice speaks the language of undeniable race and sales success, and the critics are (not so strangely) silent or at least muted. Now that Honda has announced its version of a 250cc four-stroke motocrosser and rumors abound of other colors getting on the baby-thumper train, few can afford to criticize.The YZ250F has been legal in the 125cc class since its inception, but Dirt Rider has never included it in its 125cc-class shootouts before. We were put off by production schedules not the controversy. Yamaha has always released the four-stroke models much later than their two-stroke siblings, and this didn't change for '03; the YZ250F still arrived significantly later than the YZ125. But it has uprated ergonomics and an engine that anyone can start without drama, and it now weighs even with the lightest 250cc two-strokes and only eight pounds more than the heaviest 125 two-stroke. We decided we had to wait for it. After all, inquiring minds want to know which is the real king of the 125cc class.We started with the same basic test crew as on our 250cc shootout, but we needed only six riders (one per bike to keep people from wasting time sitting), so we didn't make Tom Carson fly out from Ohio. Danny Carlson was in the body shop, so we swapped 130-pound Justin Deschamps for our flyweight tester.We always like to have the well-prepped Perris Raceway in a comparison for its great traction, wide range of jumps and rutted turns. For a true motor trial, we headed to Victorville Motorsports Compound for a track that was fast with power-robbing sand uphills and massive jumps. It was a serious motor test. We always need at least one rough track, and Los Angeles County Raceway filled the bill. We used the sandier back track at LACR for a tough engine and suspension test. The loose dirt eats up short powerbands, and some bikes go flat before you can get out of the acceleration chop or hit the first bump. Since several of the tracks had intermediate to slightly soft soil conditions, we shod all our mounts with Bridgestone M401/M402s, like those that came stock on the KTM 125 SX (some models will come with Bridgestone's M77/M78 or M59/M70), or Dunlop D756s. Both combinations were noticeably better than hard-terrain tires in the softer dirt. The Dunlops were a taste more aggressive, while the Bridgestones seemed to cross over to hard dirt better. Riding six bikes a day we had to save our riders' wrists, so we swapped to Renthal McGrath-bend handlebars on all but the KTM, since it has an oversize Renthal bar standard. After three days of testing, we herded all six bikes onto Pro Circuit's Superflow dynamometer and wrung their little necks for horsepower and torque numbers.As we learned in our 250cc-class motocross shootout, all the manufacturers have upped their game, and a strong package with a powerful and usable engine was more important than whether a machine had two strokes or four. The riders scored for subcategories (engine, suspension, etc.) on a 10-point scale, then gave the bikes an overall number grade between one and 100. To get the overall finish for each bike, we averaged the six grades. The final scores differed by eight points from first to last, and the lowest-scored machine still rated a B+.EngineEngine performance figured strongly in the final results of our 250cc-class motocross shootout, and if anything, the motors had even more of an effect here. As we always say, when you don't have much power to begin with, every little bit counts. (Of course, "not much" power is relative. Each of these machines is making numbers that would have looked right at home in a 250cc-class shootout of the mid-'80s.) Dynamometers are wonderful tools and give you a repeatable information source, and sometimes-as in the '03 250cc-class shootout-the numbers reflect exactly what we felt on the track. But there are times when the seat-of-the-pants feeling doesn't add up to the dyno chart.On the track, there was little doubt the Yamaha YZ250F was the class bully. Compared to previous Yamaha YZ250Fs, the new bike seems to make power that comes on earlier and is happier and smoother pulling at low rpm. Our riders with 250F experience were divided whether the '03 signed off earlier, but it doesn't matter. The YZ-F is muscular, tractable and strong yet civilized on the track in any condition. It clears large jumps more easily than any of the 125 two-strokes, pulls out of turns with authority and totally makes you grin under your helmet. Add the fact that now you just kick it and go, and you have the best motor in the class. The dyno bears out these impressions. The best two-stroke measured 16-plus foot-pounds of torque at just over 10,000 rpm. The YZ-F is making 17 foot-pounds at 6400 rpm, then stretches out to a meaty 18.4 foot-pounds of peak torque at 7900 rpm!Even though they don't start roosting as early as the YZ-F, four of the five two-strokes come near or even surpass the four-stroke's peak power numbers. In other words, most are not pushovers. For sure the KTM isn't. The engine received few changes for '03 (it didn't need many), but it did lose a gear from the transmission. Like the Honda and Yamahas, it is now a five-speed. The ratios didn't change, but the KTM seems to have noticeably more speed in each gear than some of the two-strokes, especially the KX. The KTM doesn't pull with much authority at very low rpm, but as it gets into the midrange it kicks butt. The middle half of the rpm range hits solidly and pulls hard. The SX mulches deep berms with a touch of the clutch and clears jumps with little effort-even jumps that had the other bikes struggling. It picks up each succeeding gear without any problems. The engine seems to go flat on top, but the dyno doesn't really show that. More likely it accelerates through the rpm faster, so it feels flat. No biggie, just shift it. The KTM's hydraulically actuated clutch is still outstanding and amazes riders who try it for the first time. Lever feel never changes.The YZ125 is only moderately impressive on the dyno, so it's lucky for Yamaha and us that we don't race on dynamometers. Just like the company's 250 two-stroke, the YZ125 is all about roll-on and response. It responds nicely to the clutch as well, so the power is always there when you need it and the motor complements the chassis in corners. Use the sharp steering to hit the inside line, then dial on that sweet power to hit your exit mark. Even when the turns are flat and bermless, the YZ shines. Every once in a while you feel a bit of a gap in the transmission, but that's rare. The YZ is a marvelous motor, and like the first two powerplants in the list, this one is good for nonstop grins.You may have noticed that Kawasaki and Suzuki are sharing some models in '03. The 125 motocrossers aren't among them, but if you didn't know better, you would swear they were! Both are six-speeds with the ratios spaced a little closer than on the other bikes. Both have decent torque feel at low rpm. Both feel stronger than the KTM when the revs are really in the basement. Above that both feel quite similar. But there are subtle differences. The KX hits harder in the middle and has a meatier feel to the power, but it runs out of boost at high rpm. The RM doesn't feel as brawny or as willing to build power quickly, but it doesn't flatten out at all on top. The differences are pretty minor, and both motors are fun and fast. But the delivery isn't as reliable as with the top three engines. We wouldn't say you lose the grin you get from the top three, but a slight look of puzzlement interrupts your smile when the KX runs out of acceleration before a jump and there is no time to grab a gear or when you hit the clutch and the RM doesn't pull as expected. Again, we wouldn't scoff at either of these motors, and the Kawasaki is a massive improvement in fun factor and competitive edge over the '02.Every rider commented that the Honda CR125R engine is a noticeable advancement over 2002. Although the engine actually makes competitive power, it feels as if that power is generated through rpm rather than torque. So the grin factor is in short supply. The engine gets the bike around the track, but the sweet spot tastes more like sugar-free. The dyno chart wasn't all smiles either. The CR was down on torque and horsepower compared to the other bikes.SuspensionThe majority of the 125cc-class weapons are suspended by KYB. The YZs, the KX and the CR are KYB bikes; the RM returns with Showa; and KTM is handled by the Dutch company WP, which is now owned by KTM. Suspension prowess was one of the areas where the Honda shone. The latest-generation aluminum frame feels good. It has a very solid and planted feel that is the opposite of flexy but still doesn't punish the rider. No doubt the well-sorted fork and shock have much to do with the confidence our riders had in the bike. The CR is more than just plush; the action is crisp, and you feel as if you can hit lines and crank turns on this bike. Forgotten factors could be the seat-the best foam and shape in the business-and the rubber-mounted handlebar. Honda learned some hard lessons from its early aluminum CRs, and we are benefiting now. The rest of the rankings are notably behind the CR, though the numbers don't necessarily mean the suspension was poor. It could be the range of adjustment was narrow or the suspension just didn't suit one or more riders. None of these bikes has major problems with bottoming or front/rear balance and most are reasonably plush, but not all suit as wide a cross section of riders.The Kawasaki is a perfect case in point. It has the most supple and reactive suspension of all the bikes. It handles braking bumps and acceleration chop with equal aplomb. So how did the Honda get ahead of it? The KX felt soft for our heaviest riders but a little stiff for the lightest. LACR had a 90-degree sweeper that dropped off one level at the turn exit. We're not talking a drop-away jump, just a spot where the track level drops roughly the distance of a normal whoop-de-do. At that point the KX felt a bit wallowy, and the rider had to chop the throttle for a second. Little riders didn't really have the same issues. Our pro testers simply found it too soft.The Yamaha YZ125 came in just a tick behind the KX, but they couldn't be more different. It feels as though Yamaha wanted control above all and was willing to sacrifice some plushness to ensure the bike would always hit its lines and stay hooked up. The chassis is very nimble and responsive, but the suspension is a big part of the equation. In the YZ125's case, the feeling that too much of the track is reaching your hands never really descends to outright harshness. Supposedly the YZ and YZ-F have nearly identical suspensions, but see the slight difference in ratings between the bikes? That is easily explained. The YZ-F's smooth power actually helps the rear suspension feel mildly better over chop exiting corners, but its fork is a bit confused. It feels a bit stiff in the initial stroke, so it doesn't want to settle into corners. At the same time the faster riders felt the fork was too soft and went through the travel a bit quickly. Adding a couple of clicks of fork rebound helped in turns but added harshness in braking bumps. The YZ and YZ-F complaints were minor, and none of the traits stopped the bikes from turning in impressive lap times for novice, intermediate and pro riders.The same is true of the RM. It worked pretty well at all the tracks. The bottoming resistance was quite good as well. Yet the faster riders felt the whole bike was too soft in spite of the fact that the 0.43kg/mm fork springs are stiffer than any bike's but the CR125R's 0.44s. Heavier riders felt a sudden spike through the fork on deep braking holes. The RM occasionally seemed a bit loose like the KX but not as pronouncedly. Otherwise, there were no real complaints. These bikes are all suspended so well that a bike with good suspension and no glaring warts ranked fifth.Keeping with tradition, the KTM has the most unique suspension setup. Not only are the components from Europe, but the SX is still the only bike with no linkage. The rear suspension is much nicer for '03, though setting it up takes a little getting used to. You need to watch the sag-rider and bike sag. The shock includes a top-out spring to help maintain traction, so you need to push down on the swingarm to get a true sag measurement. Also, the WP fork has external preload adjustment. All the adjustments can't really overcome a harshness in the fork when it encounters braking bumps. The WP fork has the softest springs, yet it lands fairly well. In fact, the rear shock feels great on landings. For part of the test we ran a softer PDS #5 progressive shock spring, and everyone up to and including 170-pound pro Keefer liked the effect the spring had on the balance and feel of the bike.HandlingWe need to be clear here: These are 125s and are all well within the ballpark, but Yamaha and Honda hit home runs. No doubt the other companies would like to know how Yamaha manages to get the YZ125 to straddle the fence between pinpoint steering and high-speed Baja stability. The thing is magic. It totally makes you feel like a hero on the track no matter who you are. The YZ is the master of the inside line, but it is still happy railing a sweeper. It jumps great, too. At Perris the YZ carved through ruts with no tendency to stand up or crawl out.The Honda was another bike without any serious flaws. It can't cut inside of the YZ125, but otherwise, it is close to perfect. It steers sharply without wanting to tuck under or wash out. It feels settled at speed, with little tendency to shake its head. This bike is calm yet nimble. The chassis feels super-solid and indestructible. Very nice performance from team red. Yamaha's YZ250F scored just a notch behind the top two bikes, and we understand why perfectly. The bike handles great but is a little heavier, so it flicks around like, well, a light 250. That isn't bad, but you do notice it-lighter guys especially. As good as these bikes are, a small "feel" issue like that costs. Also, there was that tendency for the front end to push a little and not settle. It wasn't a big problem, but it was one the riders remembered when filling out their evaluation sheets. Again, the YZ-F is a fine handler, and it seems to have an edge in stability as well.Without a doubt, no KX has ever handled the way the '03 KX125 does. The bike has a light, quick, nimble feel that is very appealing. The fun factor is definitely there. The softish suspension for the pros and heavier riders hurt its rating a little. Some of the tall riders were also a bit spooked at speed since the KX feels small overall. Again, these aren't major faults, but they are traits that affected the rating in this tough crowd.The RM is right in the same group. It, too, handles very well. The seat feels a little tall for short riders, and some riders thought the seat held them in one place too well. The biggest faults are a slight tendency to wag the front and for the rear to kick out suddenly when the rear wheel breaks traction. The joy of the chassis is the light, quick and nimble handling. Some riders loved the RM (granted they tended to be our lighter riders), and others felt their riding-style preferences didn't fit the handling.The new larger front axle and other changes have really brought the steering around on the KTM. We know the basic chassis has very capable high-speed manners. The fork's harshness on braking lumps covers up many of the fine manners of the chassis. We wouldn't turn down any of these bikes for a lack of handling.ErgonomicsWe credit Honda with starting the trend of using comfort as a speed secret, but now all of the brands pay serious attention to it. Each of our test bikes is first-rate as far as the rider's ability to change riding positions, avoid catching gear on weird edges or gaps and get up near the front wheel in turns. The ratings here reflect the different sizes and tastes of the riders as much as the actual physical makeup of the machines. One note: Our testers were all five feet nine inches or taller, so short riders may actually prefer bikes that finished lower on our list.This is another area where Yamaha has made strides. The YZ125 is slim, easy to move around on and shaped so it is very easy for the rider to maintain an aggressive body position while using very little energy. The same is true of the YZ250F. It is naturally a little wider, since the tank can't easily drop down as far on the sides due to the cylinder head being in the way. The only drawback to either machine is a seat that is somewhat minimalist when it comes to padding. The actual foam pad is both thin and firm; theYZ-F has a bit more cushion than the YZ. Yamaha has done great things with just a little padding, but riders did note the trait. Honda has the seat-foam thing down. The CR offers by far the best perch in the business. The seat has enough of the correct-density foam to benefit the suspension. The bike is slim as well. It finished behind the Yamahas because the seat/pegs/bar relationship makes the transition from sitting to standing more work. You notice standing on the Honda; on the YZ/YZ-F the action is effortless.The RM and the KX ended up with identical ratings, though they feel very different. The overall impression of the RM is a bit high and flat, as if you are perched on top of the bike. The seat has ample padding, but the shape and softness of the foam were criticized, though much less so by the lighter riders. The KX is the opposite; it has a compact layout that clearly gives a feeling of sitting down in the cockpit. The handlebar clamps are reversible, but they came in the forward position and we had no requests to move them back. Tall riders felt the bar was too close as it was. The KX is also a tight fit between the seat and the pegs, but the slim, light feel made up for that. Some riders rated the seat foam as too soft.The KTM has developed a "sitting in" feeling in place of the old "sitting on top" sensation. The bike is slim as well. KTM's team riders were all pretty stubby, so they all wanted the bar lower; our taller riders weren't as pleased and wanted the '02 Magura bar back. The SX also has a thinly padded and very firm seat that was a bane to the lighter guys and is the major reason the bike dropped back in this category.EquipmentThis category judged the bikes on the equipment they come with, the bend of the handlebar, the standard tires, the options for riding-position adjustments and how well they held up visually during the test. As expected, the KTM shone here. The 125 SX has the only powder-coated frame, plated pipe, hydraulic clutch, forged levers, aluminum handlebar and quality chain and sprockets. The new graphics showed a bit of wear, but otherwise, the bike stayed looking like new.The Honda has forged levers and uses top-grade fasteners and hardware, and it also retained its like-new looks. Big Red also stuck with the Dunlop K490/695 combination, and we still really liked those tires.Both of the Yamahas have quality hardware and popular Dunlop D739 tires, but the dark-colored bikes showed a little wear after they had been ridden. The levers are pretty nice but below the fit and finish level of the Honda's controls.Kawasaki seems to have made major improvements for '03. The hardware appears upgraded, and the bike produced little vibration and stayed looking like new. The raised ridges stamped in the frame spars minimized wear on the paint.The Suzuki also has pretty good hardware, but the stock bar crinkled easily and the levers got bent and floppy pretty easily. The graphics also showed wear after our test.Wrappin' UpSo we have a winner, but not by a knockout. If this were a boxing match, we'd have a winner by decision. On points, the bikes came out super-close. Four of our six riders picked the YZ250F, but that doesn't mean the four-stroke is for everyone. The two lightest riders chose the YZ125 first, and the points are so close because not one rider ranked it lower than second place! All of these machines have a lot to recommend them, so let's hit the high points:Honda CR125R: The best suspension, excellent handling and that super-solid chassis. The Honda is a quality piece built to high standards of durability. It is also the lightest of the bikes. The engine is a bit behind the other machines' but is competitive, and the rest of the package makes a good argument for owning one. This is a tough class, though, and our riders gave the machine the only point total in the 80s-the high 80s, but that's still a B+ in a field of A students.Suzuki RM125: This bike came in a close second in this comparison in '02, and this version is a little better. The RM is fast, turns like a dust devil and has really good rear suspension. It has plenty of competition now, but we still see the RM as an excellent choice in this class. Nevertheless, the RM didn't command the respect it earned in '02. It's almost cruel that it scored only five points (out of 100!) behind our winner yet ended up fifth.Kawasaki KX125: Brilliant chassis performance in a nimble, light (and light-feeling) package. Outstanding suspension plushness is coupled with great style. The engine is very responsive and plenty fast for most conditions. Did you notice that the powerful KTM squad in Europe just lost the 125cc World MX title to a Kawasaki? It was an '03 the green team was racing during the '02 season. Smaller or lighter riders should look hard at the KX, but our well-rounded group penciled it in an extremely close fourth.KTM 125 SX: If you are already committed to personalizing your bike, why not spend a little money dialing in the KTM suspension. A softer seat foam and a fork mod will put this bike in the hunt big-time. The engine is stronger in stock form than the other two-strokes' and feels fresher longer. Very few riders will feel the need for more engine performance than bolt-on parts provide. If the suspension were as potent as the motor, the KTM wouldn't be third.Yamaha YZ125: The only bad thing we can say is it doesn't dazzle the dyno. It brings superb handling and ride position with a great motor that is track-proven. You can't lose here, and it didn't lose with our lighter riders.Yamaha YZ250F: Absolutely fantastic power for small-bore racing in a great chassis. And now the engine starts! The youngest rider rated it fourth. Not everyone is ready to quit mixing gas, but if you are physically capable of shrugging off the eight- to 15-pound weight difference (compared to the 125s), then the YZ-F is a great choice.As always, let a great dealer or a great deal sway you; the bikes are definitely that close in performance. Also, make sure you actually sit and stand up on the bikes. The rider's size and personal preference have more to do with the ergonomic wonderfulness of each machine than the physical package does.Sales of 125cc motocrossers remain strong, so factories are motivated to keep upgrading them; we see that by the close overall ratings and the shuffling of positions in the class. This is a great time to be a 125 motocrosser.