2019 KTM 125SX. 2019 KTM TWO-STROKE FRAME All 2019 KTM SX models feature lightweight chromoly steel frames in various profiles including hydro-formed elements produced by WP Performance Systems with state-of-the-art robots. They feature optimized stiffness (2% stiffer longitudinally and 10% stiffer torsionally). The head stays are aluminum for all models (new on the 250 SX two-stroke). New frame guards improve grip and the right one is heat protector for the muffler/silencer. The subframe is 900 grams (32 ounces) lighter and 40mm longer than before. The 125/150SX engine rear can be switched back and forth between 125cc and 150cc displacement with just a cylinder, piston and head change. 2019 KTM 125/150SX ENGINE The KTM 125/150SX engine is the most powerful engine of the class, but for 2019 it gets a reworked 54mm-bore cylinder with an improved power valve system, including a sophisticated mechanism for the lateral support exhaust ports. A new layout of the exhaust ports increases the engine performance. In addition, the upper contour of the exhaust port is now machined to guaranties more accurate port timing. The KTM 125SX engine design allows an increase of the displacement from 125cc to 144cc just by replacing the cylinder, piston and head without changing the crankshaft. The new DS (diaphragm steel) clutch features a one-piece clutch basket combined with the primary gear. both milled in one piece from high-strength billet steel, the engine width at the clutch case is reduced by 10mm. The 125/150SX is fitted with a newly designed exhaust pipe and silencer. The pipe is produced with the latest 3-D stamping technology for an optimized shape. In addition the molded plastic silencer bracket is replaced by a welded aluminum bracket to reduce weight. A new airbox has been completely reworked for increased flow. This improves throttle response. The large Twin-Air air filter is mounted on a stiff cage, which minimizes incorrect installation of the filter and cage. The filter can be changed without tools in seconds. The 125/150SX are fitted with a six-speed transmission made by F1 supplier Pankl. The 38mm flat-slide Mikuni carb gets new jetting specs to adapt to the new airbox and exhaust design. Note the longer rear axles slots. 2019 BODYWORK & SEAT The all new-plastics that provide perfect ergonomics and contact points for the rider, maximum freedom of movement and improved handling. In addition, the I-beam design for the front and rear fenders are prime examples of an intelligent design, which guarantees maximum stability at lowest weight through a well thought-out structure and mounting. A newly shaped seat provides improved ergonomics and better seat comfort. Due to newly developed silicone strips the seat cover provides better feel and grip. The seat installs with one long bolt from the left side of the frame for easier removal and installation. 2019 SWINGARM All 2019 KTM big bikes models are fitted with a reworked cast aluminum swingarm featuring a longer slot for the rear axle. This allows the adjustment of the rear wheel in a position up to 5 mm further back which gives the rider the option of gaining more straight line stability for fast tracks and whoops. The single-component casting process offers low weight and a perfect flex behavior. 2019 TWO-STROKE FUEL TANKS The 125SX, 150SX and 250SX models are fitted with newly designed lightweight polyethylene tanks that improved ergonomics. Fuel capacity 1.85 gallons of fuel. 2019 COOLING SYSTEM All 2019 KTM models feature newly designed radiators which are mounted 12mm lower than the predecessors. This lowers the center of gravity and in conjunction with a new radiator shape they match perfectly with the design of the new radiator shroud to make the bike narrower and easier to get forward on the bike. Thanks to calculated liquid circulation (CFD) and improved air ventilation cooling is improved. The coolant tube, that passes through the frame, is 4 mm larger to improve coolant flow from the cylinder head to the radiators more efficient. 2019 KTM WHEELS The KTM wheels feature CNC machined hubs and high-end Excel rims, but for 2019 the aluminum nipples will feature a reworked design to reduce the frequency of spoke tightening. The tires are a Dunlop Geomax MX3S combo. 2019 KTM 250SX TWO-STROKE 2019 KTM 250SX ENGINE The 2019 250SX engine features a cylinder with a twin-valve-controlled power valve system, counter balance shaft for low engine vibration, five-speed transmission and a hydraulically operated DDS clutch. With a 66.4mm bore, the power characteristics can be changed in seconds thanks to two supplied power valve springs and a preload tension adjuster for the main spring. The 250SX engine is raised by 1-degree around the swingarm pivot improving the handling and front wheel grip. Plus, the head stays brackets are now aluminum instead of steel to reduce vibration. The 250SX gets a reworked water pump casing to optimize flow for more efficient cooling. The 250SX uses the KTM-developed damped diaphragm steel (DDS) clutch with a wear-free steel basket. This DDS design uses a diaphragm spring (Belleville washer)instead of the usual coil springs, which makes for easier clutch action. The diaphragm spring also leaves sufficient space for a rubber damping system integrated into the clutch hub, which benefits both traction and durability. The Brembo hydraulic clutch mechanism produces controlled modulation of the clutch. The 2019 KTM 250SX has a newly designed exhaust pipe and silencer. The pipe is produced with the latest 3-D stamping technology for an optimized shape. In addition, the molded plastic silencer bracket is replaced by a welded aluminum bracket to reduce weight. A new airbox has been completely reworked for increased flow. This improves throttle response. The large Twin-Air air filter is mounted on a stiff cage, which minimizes incorrect installation of the filter and cage. The filter can be changed without tools in seconds. The 38mm flat slide Mikuni carburetor has new jetting specs for 2019 to work with the new airbox and exhaust design. 2019 KTM 250SX TWO-STROKE HIGHLIGHTS Seat: newly shaped seat provides improved ergonomics and better seat comfort. Due to newly developed silicone strips the seat cover provides better feel and grip. The seat installs with one long bolt from the left side of the frame for easier removal and installation. Swingram: The 2019 KTM 250SX cast aluminum swingarm features a 5mm longer axle slot to allow the rear wheel up to 5 mm further back. Gas tank: The 250SX has a lightweight polyethylene tanks with improved ergonomics. Fuel capacity 1.85 gallons of fuel. Radiators: The radiators are mounted 12mm lower than last year to lower the 250SX’s center of gravity. The new radiators and radiator shrouds make the bike narrower. Thanks to calculated liquid circulation (CFD) and improved air ventilation the cooling is improved. Additionally, the coolant tube, that passes through the frame, is 4 mm larger to improve coolant flow from the cylinder head to the radiators more efficient. Wheels: The 250SX wheels feature CNC machined hubs and high-end Excel rims. Most importantly, the new aluminum nipples feature a reworked design to reduce the frequency of spoke tightening the spokes. The tires are a Dunlop Geomax MX3S combo. The post FIRST LOOK! 2019 KTM 125SX, 150SX & 250SX TWO-STROKES appeared first on Motocross Action Magazine.
You might think that the best bikes to aspire to ride are those of the factory stars. Wrong! The best bikes to ride are those owned and built by the factory stars’ mechanics. The mechanics’ personal bikes are almost always better than the factory bikes these top-notch mechanics build for their riders. Why? For the most part, factory mechanics are just ordinary joes who like to ride and race when they aren’t working for their superstar charges. They like silky-smooth suspension and engines that are fast but manageable. Their bikes have little in common with the bikes of the factory riders they work for. Factory riders prefer unbelievably stiff suspension, rocket-ship engines and chassis that handle best when hitting every bump head-on. You may dream of riding one of Ricky Carmichael’s National Championship bikes, but take it from guys who have ridden every one of Ricky’s works bike (from the time he was on a KX85 to the RM-Z450 he took to Loretta Lynn after he retired), you wouldn’t like it. Believe it or not, factory bikes are not the dream machines that mortal men think they are—not even close. WITH THIS IN MIND, THE MXA WRECKING CREW WENT LOOKING FOR THE DOUBLE WHAMMY—A BIKE THAT WAS ONCE OWNED BY A FACTORY RIDER BUT HAD BEEN BOUGHT AND REBUILT BY A FACTORY MECHANIC. Aesthetically, this YZ250 has a lot more black in the color scheme. Both the aluminum frame and swingarm were bothpowdercoated black. The plastics have an updated look with the R-Tech restyling kit. Ah, but the personal bike of a factory star’s mechanic is often a hidden gem. Why? These mechanics have access to unobtainable parts. They possess the knowhow to put the perfect machine together and the wherewithal to properly set up the bike to the nth degree. With this in mind, the MXA wrecking crew went looking for the double whammy—a bike that was once owned by a factory rider but had been bought and rebuilt by a factory mechanic. You can’t get much better than that. We found our double whammy via Ivan “Hot Sauce” Tedesco and Jon “Throttle” Mitcheff—and the YZ250 that they shared. Jon is a veteran mechanic and has seen it all. He worked for Pro Circuit Kawasaki as a race mechanic from 2002 to 2009. He started off working with Stephane Roncada, got his first championship with Ivan Tedesco in 2004, then moved on to wrench for Ryan Villopoto. Jon was Ryan’s mechanic for RV’s entire 250 career, where the pair won three AMA 250 National Championships and one Supercross title. When Ryan stepped up to the 450 class at Team Kawasaki, he brought Jon with him. Later, Jon became the team manager for the Valli Yamaha team and is now currently back at Pro Circuit. Ivan never got to ride his 2013 YZ250. He had a box of cool aftermarket parts and the best intentions, but Ivan was never able to pull the trigger. So, Jon stepped up and made a handshake deal to take the bike and the box of parts off Ivan’s hands for $3500. When Jon stopped by Ivan’s house to pick up the bike, it was literally in pieces, but for a factory mechanic, that was no big deal because it saved Jon from having to take it down to the frame himself. THE GEAR: Jersey: AXO Motion vented, Pants: AXO Motion vented, Helmet: 6D ATR-1, Goggles: EKS Brand EKS-S, Boots: AXO A2. Jon had another ace in the hole. He was friends with Mitch Payton and was free to roam the nooks and crannies of Pro Circuit’s race shop. There were rows of exhaust pipes stacked up for miles. The engine department had cylinders, heads and cases for every bike ever made. And, in the suspension department, Bones Bacon had shims for every fork and shock on the planet (and a book full of notes about how to put them together). And stashed away in the race shop’s upper deck was a boatload of unobtanium. Mitch never sells any of his trick stuff. He stores it, forgets where he put it and moves on to stashing newer stuff. When Jon looked through the shop, he found some hidden treasures for his YZ250 build. There was a full titanium bolt kit, works Showa forks and Chad Reed’s old carbon/titanium YZ250 silencer. Jon showed the parts to Mitch and was surprised when Mitch said, “They’re yours.” WHAT WAS IT LIKE TO RIDE? IT WAS EVERYTHING WE WISH A YZ250 COULD BE, WITH THE CAVEAT THAT THE YZ250 HAS THE OLDEST LIVING CHASSIS STILL IN PRODUCTION TODAY. Both the head and cylinder were ported and polished by Mitch Payton himself. The engine was playful yet powerful. The trickest parts on Jon’s YZ250 build were an Italian-built CRM Composite tank and ignition cover. The rest of the build included Duyba-built wheels, updated R-Tech plastic, a Works Connection perch mated to a handmade ARC lever, Renthal bars, Kite triple clamps, a Pro Circuit pipe, EBC 280mm oversize front rotor and a Pro Circuit clutch cover—and much more. What was it like to ride? It was everything we wish a YZ250 could be, with the caveat that the Yamaha YZ250 has the oldest living chassis still in production today. Since the chassis was designed back in 2006, the handling is not as sharp as what’s available on the newer smokers on the track. It was not bad by any means; however, band-aid fixes had to be used to stop the bike from shaking at speed without sacrificing turn-in. The Factory Showa forks and Mitch’s magic hands on the cylinder and head distracted us from the aspects of the YZ250 that felt old-school. This is a one-off Pro Circuit titanium/carbon fiber silencer that Chad Reed ran on his 2005 factory Yamaha YZ250. MXA test riders believe the stock Kayaba SSS forks are the highest standard, but as good as they are, they can’t hold a candle to Jon Mitcheff’s scavenged Showa factory forks. In the rough chop, it felt like the MXA test riders were riding on clouds. The forks were super supple yet held up on harsh hits. Now you might think that the metallurgy, close tolerances and fancy coatings on the works forks were what made them feel so good—not so. Forks are only as good as their valving, and works forks with bad valving aren’t any better than stock forks with bad valving. Luckily, Bones Bacon worked with Jon to make the Showa forks and Kayaba shock perfectly balanced. Jon is still in the process of locating a one-off factory Showa shock to match the forks. Until then, we loved the sweet sensation of his mixed suspension components. LOVED IT. LOVED RIDING IT. LOVED LOOKING AT IT. LOVED SITTING ON IT AND GOING “VROOM.” THIS BIKE IS LITERALLY PRICELESS. The 2013 YZ250 has poor braking components compared to today’s Brembo standards. A 280mm EBC oversize front rotor was used to bump up pucker power. Mitch crafted the YZ250 engine so that it would be manageable for mere mortals. Jon could have had Mitch build him a 2005 Chad Reed replica engine, but Jon was smart enough not to ask for it. Good thing, too, because MXA tested Chad Reed’s 2005 Factory YZ250 back in the day. It was a light switch. It was temperamental, hard-hitting and too much for anyone of lesser talent than Skippy. Jon’s engine was nothing like Chad’s, even though Jon had the silencer. It ran with the same curve as the stock powerband but with the dips filled in and the power raised significantly throughout the entire rpm range. It even had improved over-rev. The power had flair that made the bike fun to ride. Our testers felt the Pro Circuit-built engine would easily run with, or outpower, a new-age KTM 250SX. Loved it. Loved riding it. Loved looking at it. Loved sitting on it and going “vroom.” This bike is literally priceless. You would empty your bank account locating and buying these factory parts off the dark web; however, most of the upgrades are simple, blue-collar improvements. This build, without its one-off trickery, would still be a sweet machine. Two-strokes are the working man’s machine, and this one just had a sweet tooth for titanium and carbon fiber. Bones Bacon revalved the factory Showa forks to work with the Kayaba SSS shock. The balance was fantastic. YZ250 PARTS SUPPLIERS www.procircuit.com www.worksconnection.com www.rtechmx.us www.ebcbrakes.com www.n-style.com www.renthal.com www.asvinventions.com www.vpracingfuels.com www.dunlopmotorcycletires.com www.crmcompositi.com www.dubyausa.com The post WE RIDE A FACTORY MECHANIC’S 2013 YAMAHA YZ250 TWO-STROKE appeared first on Motocross Action Magazine.
This test is from the January 2000 issue of MXA. QUESTION ONE: IS THE ‘00 ENGINE FASTER THAN THE ‘99? Unfortunately, no. In truth, it’s not much faster than the KTM 125SX. QUESTION TWO: WHAT’S WRONG WITH THE KTM 250SX ENGINE? Just about everything. It has a lazy powerband that begs for an odometer and route chart. With the exception of a little burp of power when rolling the throttle on, there is not much to rave about. After the lively little hit, which is only really good for goosing the engine through the pits, the 250SX powerband delivers a short, flat, monotone-style of power. QUESTION THREE: WHAT DID KTM CHANGE ON THE ‘00 ENGINE? Everything! The most significant change was to the bore and stroke. KTM’s R&D department dropped the previous 67.5mm by 69.5mm bore and stroke for the more common 66.4mm by 72mm dimensions. This change alone necessitated new cases, cylinder, head, crankshaft, rod, piston, rings and pipe. While KTM was tossing out the old and ringing in the new, they made these changes: (1) Increased the size of the water jacket (around the cylinder) to improve cooling. (2) Shortened the connecting rod from 132mm to 129mm (rod length is not necessarily related to bore and stroke). (3) Reduced crankshaft weight by inserting two tungsten inserts as stuffers. (4) Cleaned up the reed intake channel to optimize fuel flow. (5) Outfitted the engine with a Kokusan 2K4 ignition with a magnetic Power Jet solenoid to control the new, 38mm, Air Guide Keihin carb. QUESTION FOUR: WHAT DO THE CHANGES MEAN? Sadly, very little. What is most surprising is that last year’s 250SX engine was a good piece. Although not blessed with stump pulling low-end, the ‘99 250SX growled into a sharp, aggressive, crisp and hard hitting midrange (with a pretty sweet over-rev). So why change it? Perhaps KTM felt that the ‘99 engine had run its course and they needed something for the future. However,12 months ago, KTM’s engineers totally redesigned the ‘99 250SX engine. Those changes included: (1) A newly designed reed block assembly. (2) A smaller exhaust port to increase spent gas velocity. (3) Lighter piston. (4) Narrower power valve flapper. (5) Redesigned cylinder head squish band angle. And (6), Reduced crankshaft weight. Surprisingly, All that development work, which actually enhanced the powerband of the ‘99 KTM, was thrown away in favor of a totally new engine. And the results are dismal. QUESTION FIVE: IS IT AS FAST AS A JAPANESE 250? No! At best, it’s as fast as a Japanese enduro bike. KTM should have sat on their new engine for another season of testing. Last year’s engine was twice as competitive as this year’s. QUESTION SIX: WHAT ABOUT THE JETTING? We pinged. It was hard for the MXA wrecking crew to imagine that an engine this mellow could detonate under a load, but it did (perhaps because it had to be ridden at ten-tenths all the time). Here is the jetting we ran in our KTM 250SX: Mainjet: 172 Pilot jet: 48 Needle:NOZF NOZE Slide: 6.0 Air screw: 1 1/2 Clip: groove number 3 QUESTION SEVEN: WHAT ABOUT THE HYDRAULIC CLUTCH? The MXA test crew prefers hydraulic clutches to manual ones, but not for the reason that you might think. If you imagine that hydraulic clutches are easier to pull than regular clutches, you are wrong. They aren’t. If you assume that they feel better than manual clutches, you are wrong. In truth, a hydraulic clutch is a little firmer than the smoothest of the standard clutches and, it has a distinctly different feel. However, the differences between an RM, YZ, KX and CR clutch pull are no less significant. What a hydraulic clutch does offer is a consistent feel over a long moto. It resists the temptation to go slack, get mushy or tighten up. Sweet, very sweet. QUESTION EIGHT: WHAT ABOUT THE PDS REAR SUSPENSION? KTM doesn’t use shock linkage and we don’t care. The whole idea of rising-rate, wishbone, rocker-arm, pull-link suspension systems is overblown. To achieve an effective rising rate, motorcycles don’t have to have complicated linkages. KTM proves it. By positioning the shock within the known framework of a scalene triangle (one in which the sides have different lengths and angles) a suspension designer can duplicate the rising rate of any linkage system. And, if he’s a smart designer. he won’t duplicate the current crop of leverage ratios, but aim for something with a straight rate. KTM has tried to do this. They haven’t totally perfected it, but they are a far sight closer than the Japanese engineers (who switch leverage ratios every other year–almost always returning to one they tried a few years before–and then dropping it and moving on to the next magic, but elusive, number). It might sound strange, but don’t worry about the lack of rear shock linkage. It’s not necessary. What are the advantages of a single-sided, no-link, rear suspension system? (1) Less complexity and fewer moving parts. (2) Future rising-rate changes can be accomplished by moving the lower shock position (rather than redesigning a complicated linkage). (3) Shock access is excellent. (4) The suspension becomes damping dependent instead of rate dependent. (5) The one-sided shock makes room for a straighter carburetor tract. QUESTION NINE: HOW GOOD IS KTM’s NO-LINK PDS REAR SUSPENSION? Much better than it was when KTM first adopted the idea. Outfitted with an Ohlins-conceived dual-piston shock (licensed by WP), the KTM rear suspension is good. Since the complete system is dampening dependent, as opposed to the Japanese method of altering the rising rate from year to year to try and induce improvement, KTM has made steady strides in dialing in the dual-piston shock. If there is one thing we would change, it is the stock progressive-rate shock spring. We’d opt for a straight-rate. A straight-rate spring will stop the KTM’s tendency to drop into its stroke and bang around in mid-sized bumps. It’s a good idea. What was our best shock setting? Spring rate: 8.3/ 11 kg/mm Race sag: 95mm Compression: 3 clicks out Rebound: 20 clicks out Notes: Common sense and years of experience tell a rider that turning the compression clicker in (clockwise) will stiffen the compression damping. Not so on a KTM. You turn the clicker out for more compression and in for less. QUESTION TEN: WHAT DO WE THINK OF THE ‘00 WP FORKS? First, we are a little miffed that KTM threw in the towel on its ‘99 right-side-up fork. That is a shame. KTM’s 50mm, conventional, WP forks were winners. They were the best forks of ‘99–hands-down. But, they are gone for ’00, replaced by 43mm, upside-down, WP forks. How good are the new forks? Not as supple or responsive as last year’s unit, they are still workman-like forks. The new forks feel a little harsh on low-speed compression and too quick in the mid-stroke, but they absorb hard landings well and are competitive with any other brand of fork offered in 2000. What was our best setting? For hardcore racing we recommend this set-up: Spring rate: 0.40 kg/mm Oil height: 140mm Compression: 14 clicks out Rebound: 14 clicks out Fork leg height: 10mm above triple clamp Notes: Unlike last year’s conventional forks which had way weird adjuster placement, the new WP upside-down forks mimic Kayabas (compression on the bottom and rebound on the top). QUESTION 11: WHY DID KTM SWITCH FROM RIGHT-SIDE UP FORKS? If KTM had the best forks in ‘99, why did they switch to upside-down forks for ‘00? Because of you. Not you personally, but the collective you. The great unwashed masses that make up the buying public want upside-down forks. The American consumer believes that upside-down forks work better than right-side-up forks. They are wrong (Suzuki and KTM both had better fork performance when they were right-side-up), but when it comes to laying down cold hard cash, the customer is always right. Is there an advantage in KTM’s switch to upside-down forks? Yes. Upside-down forks are several pounds lighter than conventional forks. QUESTION 12: HOW DOES IT HANDLE? KTM handling is an area that can’t be danced around. The Austrian bike does not handle like a Japanese motocross bike. This is most noticeable on tight, twisty tracks, but is equally evident in any sharp corner. It doesn’t turn as quickly as an RM, YZ, CR or KX. And, with its enduro powerband, it’s best not to dive into the inside and try to drag race your competition out of a turn. Better to slide the corners, seek the outside line and try to maintain momentum. There is something intrinsically strange about the first few minutes on a KTM chassis (although we don’t feel the same way about the smaller, lighter and more agile KTM 125SX). The 250SX feels different than a Japanese bike. Not wrong. Not bad. Not awkward. Just different. After about 30 minutes of riding, the out-of-sorts sensation goes away and the balance points become more natural. Even if it’s not as quick on the inside as its competition, it really shines at high speed. It’s a very stable platform. QUESTION 13: WHAT DID WE HATE? The hate list: (1) Color: We have grown to like the orange, but we will need a few more years to dull our aesthetic tastes to the point where we can accept the silver side panels, rear fender and fork guards. (2) Front fender: KTM’s front fender looks awful. Who ever came up with its forked tongue design deserves a promotion–to any KTM division outside of the design department. (3) Gas cap: The gas cap is too small. (4) Radiator wing: The rear corner of the radiator wings hook on your leathers. The quick fix is to trim the very back edge (where the seat and tank meet) so that the radiator shroud has a rounded corner. (5) Side panels: When the aftermarket designers start offering trapezoid-shaped digits, the KTM side panels will be in vogue. Until then, no matter how you angle the numbers, it’s wrong. (6) Shock bolt: If you are standing by a track when a KTM 250SX goes by, look down at the ground. Most likely you will find the bike’s top shock bolt. (7) Silencer: We have lost enough silencer end caps to stock a dealership. Take our word for it, tighten the sand-cast end cap before every race. (8) Exhaust pipe: KTM might be suffering a bout of oxygen embrittlement on their exhaust pipes. We saw two pipes that cracked at the bottom exhaust pipe spring. Since the KTM has three springs, we removed the bottom one and didn’t suffer a failure. (9) Clutch lever: KTM spec’ed a diminutive, two-finger clutch lever for 2000. It’s too small. Luckily, last year’s full-size clutch lever fits. QUESTION 14: WHAT DID WE LIKE? The like list: (1) Airbox: KTM’s no-tools-needed airbox could use a touch more engineering, but it’s cool not to have to remove the seat to get to the filter. Watch the dzus-style fasteners–they disappear faster than pens at sign-up. (2) Handlebars: The KTM is the only one of the Big Five to come stock with aluminum handlebars. Very cool. (3) Tires: Bridgestone M77/78 are good intermediate terrain tires. We like this sneaker combo (although we like the rear more than the front). (4) Frame guards: KTM includes plastic frame guards on every bike. (5) Brakes: What a difference! Finally, KTM has addressed their brake problems. Thanks to a new front master cylinder, smaller diameter hydraulic line and new rotor, the front brakes are one-finger powerful. Even better, KTM put a larger piston in the rear master cylinder to cut down on hydraulic pressure in the line. The result? The brake can no longer be used to turn lights on and off. Better modulation and less lock-up are long overdue. (6) Preload ring: Instead of using two rings, which lock against each other, KTM has a very thick single ring which clamps to the shock body via an Allen bolt. This is a good idea and makes adjusting spring preload easier. (7) Clutch: It’s hydraulic. Enough said. (8) Chain adjuster: KTM designed eccentric chain adjuster blocks that can be turned around when the chain stretches. Additionally, they have a very long axle slot to accommodate massive wheelbase changes. (9) Bar mounts: KTM’s new triple clamp features adjustable bar mounts. This allows the rider to fine tune the fit. We ran the bars all the way forward. QUESTION 15: WHAT DO WE REALLY THINK? What do we think? We don’t think the new engine is ready for prime-time. If the 2000 KTM 250SX came with the 1999 engine, it would be a runaway hit. As is, it is a disappointment. The post TWO-STROKE TUEDAY | 2000 KTM 250SX TWO-STROKE appeared first on Motocross Action Magazine.
This bike test is from the December 2006 issue of MXA. It is easy to look at the 2007 Suzuki RM125 and see a throwback to an ancient era. You don’t have to be an archeologist to catalog the relics: steel frame, revvy powerband and unchanged exterior. The RM125 is getting long in the tooth when compared to the Yamaha and KTM. Yamaha went all-out on a totally new bike in 2005, and KTM threw the complete chassis away and started over in 2007. Perhaps from a business point of view, it doesn’t make sense to invest valuable R&D money into 125cc two-strokes anymore, especially when the market has gone goo-goo over four-strokes. And Suzuki obviously had bigger fish to fry with the release of its all-new, Suzuki-built, aluminum-framed RM-Z250 this year. That makes the RM125 a lame duck—even though it’s not a politician. Faced with shifting market trends, decreasing two-stroke sales and better uses for its R&D money, the 2007 Suzuki RM125 is destined to face the world with nary a mod. Is doing nothing enough to save the RM125? The MXA wrecking crew decided to find out. Q: DID SUZUKI MAKE ANY CHANGES TO THE 2007 RM125? A: Yes, but you aren’t going to have to hold onto your hat when you hear the list. (1) Seat cover: For 2007, the seat cover has a textured pattern on it to improve grip. (2) Graphics: Normally we wouldn’t mention that the tank decals are different for ‘07, but the list of changes is so small that we feel the need to pad it. (3) Fork guards: The front fork guards are lighter than in ‘06. Q: WHAT DO THESE MODS MEAN ON THE TRACK? A: Nada. But last year Suzuki gave the RM125 some love with a stronger piston ring knock pin, narrower reed valve passage, new exhaust pipe, hopped up CDI map, Renthal FatBars and stiffer suspension settings. As for the ‘07 mods, if you can figure out how to go faster by virtue of gripper side panels on the seat, you are on to something. The 2007 Suzuki RM125 only received small changes since the bike was on its way out. Q: IS THE 2007 RM125 FASTER THAN THE 2006 MODEL? A: No. Q: HOW DOES THE 2007 SUZUKI RM125 RUN? A: The engine does its best work from the midrange on up. Although the low-end has been improved considerably over the years (thanks to the 2006 cylinder changes), this isn’t a torque-monster. RM125 riders will have their best luck holding this bad boy wide open, fanning the clutch and listening to the engine sing. You’ll be living on the edge, but sometimes that’s the only thing that makes life worthwhile. Is the 2007 RM125 engine competitive? Yes, but just barely. It is at its best as an entry-level 125cc machine for young riders making the jump up from the mini ranks or for someone in the market for a fun bike that will be cheap to maintain. Q: WHAT IS THE WEAK LINK OF THE RM125 POWERBAND? A: It doesn’t like a load. On flat, hard ground the RM125 is as fast as any other 125, but throw in a hill, soft sand or deep loam, and it struggles. The engine does its best work from the midrange on up. Although the low-end has been improved considerably over the years. Q: WHAT IS THE CHEAPEST WAY TO IMPROVE THE 2007 RM125 POWERBAND? A: Gearing. Depending on your local track layout, the RM125’s gear combos can be configured to give you drive for tight tracks or rev for long tracks. We think every Junior level rider should gear it down one tooth. Q: WHO MAKES THE BEST SUZUKI RM125 PIPE? A: Go with FMF. Their pipe doesn’t waste any time trying to make the RM125 into something that it isn’t—it gives the RM more where it already has the most. With more mid-and-up, the RM125 can hang longer in each gear. Call FMF at (310) 631-4363. Q: MOTO TASSINARI OR BOYESEN RAD VALVE? A: MXA’s RM125 test pilots prefer the Moto Tassinari reed. This is a worthwhile mod that makes a noticeable difference in the meat of the powerband. Q: WHAT ABOUT THE JETTING? A: No big hassles. Here are the stock RM125 jetting specs: Main Jet: 370 Pilot Jet: 40 Needle: 6CHY17-60 Clip: Second from top Air screw: 1-3/4 turns out On flat, hard ground the RM125 is as fast as any other 125, but throw in a hill, soft sand or deep loam, and it struggles. Q: HOW MANY GEARS DOES THE 2007 RM125 HAVE? A: It’s a sixer! Good thing, too. Suzuki’s power output isn’t really potent enough to pull widely spaced gears, so the close-ratio six-speed magnifies the power and places it at the rider’s left foot. Stir the lever or go slow. Q: HOW GOOD IS THE SHOWA SUSPENSION? A: MXA test riders used to dread riding the RM125. The suspension settings were so soft that with a fast rider onboard it bucked like a Model T on a washboard road. Thankfully, back in 2006, Suzuki got on the stick and added some damping versatility for a wider range of riders—not just minicycle refugees. Stiffening the valving on the forks and adding a stiffer shock spring were good things for the average-sized 125 rider. And, if you are a mini munchkin, all you have to do is turn the compression clickers out on the forks and shock to get it more supple. Q: WHAT WAS OUR BEST FORK SETTING? A: Even though the fork valving is stouter, most MXA test riders still wanted to go up on the spring rates. We swapped the stock 0.42 kg/mm spring for stiffer 0.43s. This is a must-do mod for fast racers, as well as heavier riders. The stiffer springs make the forks ride higher in their stroke and just give the bike a more balanced feel. To complement the stiffer fork springs, we chose to set the compression and rebound clickers at ten out. For hardcore racing, we recommend this fork setup: Spring rate: 0.43 kg/mm (0.42 stock) Oil height: 335cc Compression: 10 clicks out Rebound: 10 clicks out Fork leg height: 5mm up Q: WHAT ABOUT THE REAR SUSPENSION? A: Thanks to the stiffer spring, which was added last year, the rear of the RM125 is twice as good as it was back in 2005. The 2007 shock, valving and spring are unchanged from ’06. The rear suspension is fairly decent on the RM125, but you need to pay attention to the compression clickers. Q: WHAT WAS OUR BEST SHOCK SETTING? A: For hardcore racing we recommend this shock setup: Spring rate: 5.1 kg/mm Race sag: 100mm Hi-compression: Two turns out Lo-compression: 12 clicks Rebound: 10 clicks Even though the fork valving is stouter, most MXA test riders still wanted to go up on the spring rates. We swapped the stock 0.42 kg/mm spring for stiffer 0.43s. Q: HOW DOES THE RM125 HANDLE? A: The 2007 RM125’s chassis exhibits some really great traits. It corners like a scared rabbit and it flies like a bird. The RM125 is the epitome of agility, quickness and poise. It’s a little busy at speed, but it feels so light and well balanced that the little wiggle in the whoops is easily controlled. Thanks to its flat-out powerband and nimble chassis, the RM125 lends itself to total commitment. It has to have cat-like reflexes to run with the man-eaters that are after the herd. It doesn’t have the kind of power to pull a 250F out of the corner, so an RM125 rider must hone his later braking, wide-open, kamikaze approach to corners. Q: WHAT DID WE HATE? A: The hate list: (1) Power. This isn’t our first pick as a powerhouse 125. Although better than the anemic Honda CR125 mill, it plays third fiddle to the stronger YZ125 and KTM engines (and doesn’t come close to any 250 four-strokes). Where does it rank on the hierarchy of power? If we were to throw all the 250Fs into the 125 mix, the RM125 would be eighth on the list. (2) Gearing. The RM125 needs help for tight tracks, deep loam or tracks with hills. (3) Clutch. This bike needs stiffer clutch springs. Q: WHAT DID WE LIKE? A: The like list: (1) Handlebars. Oversized Renthal Fatbars are a nice touch. (2) Feel. Although not the lightest 125 made, the RM125 feels like a feather on the track. (3) Brakes. Suzuki has dialed the brakes in. A great front brake. Q: WHAT DO WE REALLY THINK? A: Let’s sugar-coat the 2007 Suzuki RM125 for a moment. It has traits, sensations and characteristics that don’t exist in this crazy mixed-up four-stroke world we live in. It is a fun bike to ride, cheap to maintain and not the least bit intimidating. But, underneath the sugar-coating is a bike that hasn’t been at the top of the 125cc two-stroke world since 1995—and four-strokes have changed the landscape drastically since then. It is a good buy for someone looking for a low-cost race bike that is yellow. The post ON RECORD | WE TEST THE 2007 SUZUKI RM125 TWO-STROKE appeared first on Motocross Action Magazine.
The MXA wrecking crew rook our 2018 Yamaha YZ125 out to Glen Helen Raceway for a chance to turn laps without anyone on the track—except other MXA test riders. That way, you get to hear the undiluted shriek of the venerable YZ125 engine at full tilt. It may not be the fastest 125 smoker on the showroom floors, but until they race start racing linoleum floors, bikes will be judged by how well they do on the track. Judge for yourself. The post MXA FIRST RIDE VIDEO: 2018 YAMAHA YZ125 TWO-STROKE RAW appeared first on Motocross Action Magazine.
This story is from the January 1999 issue of Motocross Action Magazine. 1999 KTM 125SX TWO-STROKE SPECS Engine: Water-cooled, 124.8cc, two-stroke, reed-valved engine. Bore and stroke: 54.25mm by 54mm. Transmission: Six-speed, wet clutch. Suspension: 13.4-inch WP 50mm conventional forks and 11.8-inch WP shock Wheelbase: 57.56 inches. Claimed weight: 199.8 pounds. Price: $4998. Those are the tech specs, but these are the questions that most riders want the answers to: QUESTION ONE: IS THE ’99 ENGINE FAST? Fast enough to get from point A to point B ahead of the rest of the 125 pack. Last year’s KTM engine mimicked the power of a CR125. For ’99, Honda should have copied the KTM. With the same Honda-ish characteristics as the ’98, KTM’s ’99 125 blows the lid off of a Honda. The engine is dead down low, but it hits with authority in the middle and revs into the ionosphere. QUESTION TWO: IS THE ’99 ENGINE BETTER THAN THE ’98? A little. After such great success with a brand new engine in ’98, KTM wasn’t about to dump it all and start with something different for ’99. The power characteristics are the same as in ’98–with improvements. Like Yamaha, KTM has designed a good engine. Now all they have to do is a little tinkering (like Yamaha has done since ’96) to make it great. The 1999 KTM 125SX engine got from point A to point B faster than its competition. QUESTION THREE: WHAT DID KTM DO TO THE ’99 ENGINE? Since KTM revamped the 125SX in ’98, there weren’t a lot of engines changes for ’99. However, KTM did make a few: (1) The 125SX gets a newly designed reed block assembly. It features a two-petal reed assembly and horizontal vanes in the intake tract (a la Honda). The new reed should improve throttle response. (2) The hydraulic clutch, which was tested on the 125SX last year, has proved to be completely reliable. (3) To improve shifting, KTM switched to an all-new shift fork design. The ’99 shift fork uses spring loading to reduce drag and lower the friction coefficient. How? Small springs at each end of the shift shaft suspend it to allow each gear to engage without resorting to excess undercut on the dogs. QUESTION FOUR: WHAT DO THE CHANGES MEAN? You can shift with ease, fan the clutch to your heart’s content and feel the engine be more responsive. In ’98 the Hydraulic clutch on the 125 was the test bed for the big bikes. For ’99, it is the standard by which every clutch is measured. Easy pull, no fading and consistency make the hydraulic clutch a work of art. KTM has come a long way in the shifting department, but they still have a little further to go. Despite the ’99 being easier to shift than the ’98, it still isn’t as responsive as a Yamaha or Suzuki. However, it is on par with the KX and light years better than the CR. QUESTION FIVE: DOES THE ’99 REV FARTHER? Why would you want it to? The ’98 KTM revved forever. The ’99 still revs forever. QUESTION SIX: WHAT ABOUT THE JETTING? Way off. For SoCal’s sea level tracks we had to lower the main jet, pilot jet and raise the clip one position to get the KTM to run crisp. This was our best setting: Mainjet: 185 Pilot jet: 45 Needle: NOZH Slide: 6.0 Clip: Groove number 2 Air screw: 2 turns Note: KTM’s are very responsive to jetting changes. If your bike feels sluggish, keep changing the jetting till it barks. The stock jetting of the KTM 125Sx carb was horrible. It took some time to clean the jetting up. QUESTION SEVEN: WHAT ABOUT THE NO-LINK SUSPENSION? Don’t obsess on the lack of a rising-rate linkage. It doesn’t mean much. By positioning the shock within the known framework of a scalene triangle (one in which the sides have different lengths and angles) it is possible for KTM to duplicate the rising rate of any linkage system. The advantages of the no-link, one-sided system are: (1) Less complexity and fewer moving parts. (2) Future rising rate changes can be accomplished by moving the lower shock position (rather than redesigning a complicated linkage). (3) Shock access is excellent. (4) The one-sided shock makes room for a straighter carburetor tract. Two years ago Ohlins developed a special twin-piston damper to use with the no-link system. So why does the KTM have a WP (White Power) shock? Three reasons: (1) KTM owns White Power. (2) Ohlins couldn’t or didn’t want to produce the shock for the price. (3) KTM licensed the technology from Ohlins and had WP build the shock. The KTM shock features two damping pistons (instead of one). One piston is speed sensitive (to the speed of the oil rushing through it). The second piston is position sensitive (to the location of the shock shaft). How does the WP shock know which piston to listen to? A tapered rod runs down through the shock shaft and half way through the shock’s stroke the rod activates both pistons (prior to halfway only the speed-sensitive piston is operational). QUESTION EIGHT: HOW WELL DOES THE NO-LINK WORK? Better than most linkages. Boy, what a difference a year makes. The original No-Link PDS system was flawed from the get-go. Not due to placement, positioning or spring rates, but bad valving. One generation later KTM has sorted out the bugs, redesigned the piston and delivered a No-Link rear suspension system that is better than most of its competitors’ linkage systems. The PDS WP no-link rear suspension always got a bad wrap, but it has its advantages. QUESTION NINE: WHAT WAS OUR BEST SHOCK SETTING? What was our best shock setting? For hardcore racing we recommend this shock set-up: Spring rate: 7.6/11 kg/mm Race sag: 95mm Compression: 6 clicks out Rebound: 14 clicks out Notes: Common sense and years of experience tell a rider that turning the compression clicker in (clockwise) will stiffen the compression damping. Not so on a KTM. Turn the clicker out for more compression and in for less. All in all, the ’99 PDS system receives a good rating. It works best with minimal compression damping. QUESTION TEN: HOW GOOD ARE THE NEW FORKS? Gone are the wimpy 45mm Marzocchi conventional forks and in their place are 50mm WP conventional forks. This is a great change. The ’98 Zokes worked well, but suffered from terminal maintenance problems. The Dutch-built WP’s work very well, without the blown seals, warped shims and questionable metallurgy of their Italian counterparts. Is there a downside to the WP swap? Yes. Weight. The 50mm WP forks weigh 7 pounds more than the Marzocchi 45’s. Can that weight be felt? Yes, but since the WP forks work so much better, it is a small price to pay. QUESTION 11: WHAT ARE THE BEST FORK SETTINGS? What was our best setting? For hardcore racing we recommend this set-up: Spring rate: 40 kg/mm Oil height: 150mm Compression: 11 clicks out Rebound: 10 clicks out Fork leg height: 3mm above triple clamp Notes: There is something to be said about 50mm forks. Because of the 125’s smaller size, flex is slim to none. Out of the crate, KTM is the only company with good spring rates, valving and clicker settings. 1999 was a big year for the KTM 125SX. It made huge improvements to the bike and became competition for the Japanese manufactures. QUESTION 12: HOW DOES IT HANDLE? Like a Japanese bike. If you were expecting the same old line about how KTM’s feel tall and flop through the turns, guess again. The KTM 125 still doesn’t crave tight turns, but it will carve when asked to. European GP testing and a slightly slack head angle keep the KTM stable on the high speed stuff. KTM gets kudos for their aluminum bars and handlebar bend, but they fail miserably in the categories of bar height and placement. The bars feel low–so low that the sensation of going over the bars never goes away. We ditched the stock bars for a set of Honda highs. If that doesn’t work, KTM recommends switching to an Applied KTM top triple clamp that moves the bar clamps up 5mm and forward 10mm. KTM has been fine tuning their easy access air box design for years now. QUESTION 13: WHAT DID WE HATE? The hate list: (1) Color: We like orange. Orange and black is okay (although it smacks of Halloween and Harleys). However, we draw the line at orange, black and silver. Let’s lose one of the three. (2) Fork guards: We kind of hope that WP would make a front number plate/fork guard combo similar to Suzuki’s. (3) Front fender: Earth calling! The worst looking fender in the universe. (4) Rear fender: The gray rear fender turns white in blotches. It gets ugly fast (plus why is it gray in the first place). (5) Gas cap: The gas cap is too small. (6) Radiator wings: The rear corners of the radiator wings hook on your leathers. (7) Side panels: Whoever designed the trapezoid shape of the KTM side number plates never put a number on a bike in his life. No matter what angle you put the numbers on it’s wrong. (8) Turning radius: When turning left, the fork tubes hit the ignition black box. Since there is no black box on the right side, the KTM can turn farther in that direction. Come on guys, move the black box. (9) Air filter: We love the easy access airbox, but on several occasions our Twin-Air filter was pushed off the edge of the cage while pushing the D-shaped cage into the airbox. Always check around the edges for air leaks. In 1999, KTM was one of the only manufactures using solid aluminum bars. However the bend was much too low. QUESTION 14: WHAT DID WE LIKE? The like list: (1) Clutch: It’s hydraulic. Good thing, because the Honda-style power requires lots of clutch work. This is the clutch of the future. (2) Airbox: It’s cool not to have to remove the seat to get to the filter, but be very careful that the recess cage doesn’t knock it off when putting the air filter in. (3) Handlebars: The bars are aluminum–very cool, but too low. (4) Tires: Bridgestone M77/78 are very good intermediate terrain tires. We like this sneaker combo. (5) Silencer: Very quiet. When you combine the lack of low-end and the absence of sound, it’s eerie. You gas it just to make sure it’s running. (6) Frame guards: KTM and Kawasaki are the only manufacturers to include plastic frame guards to protect the paint on the tubes. (7) Brakes: We have often referred to KTM brakes as “Euro brakes.” What are Euro brakes? Ones that you have to pull on with more effort than “Japanese brakes.” For ’99 the KTM brakes are powerful enough to avoid the Euro nomenclature. The front is powerful and, for a change, the rear isn’t a light switch. (8) Shock preload: Instead of two interlocking preload rings, KTM uses one thick single ring (which clamps to the shock body via an Allen bolt). To adjust the spring preload you loosen the Allen bolt, turn the preload to the correct sag and then tighten the Allen. However, you can’t tighten the Allen if you don’t make a full revolution with the preload ring. QUESTION 15: WHAT DO WE REALLY THINK? Let’s review. Engine: Like a Honda but better. Don’t try and lug the KTM. Once you get in the midrange you will be infatuated, and when you hit the top end you will think it’s true love. This is a good midrange and up engine. Handling: Sitting on the KTM it feels tall. Riding it you think the front is too low. Once you fix the handlebar problem with a new set of bars, you will find a bike that does nothing remarkably good or bad. Suspension: This bike has top-notch suspension. The new 50mm WP Extreme forks handle small and big bumps alike. The rear suspension, although not as silky smooth as the front, handles bumps with a consistent demeanor as long as you don’t get confused and turn the compression adjuster the wrong way. Overall rating: Last year KTM shocked everyone with a 125 that was competitive with the Big Four. This year, the KTM isn’t just competitive, it’s better than most of the big four. Welcome to the party. The post TWO-STROKE TUESDAY | 1999 KTM 125SX TWO-STROKE RACE TEST appeared first on Motocross Action Magazine.
The 125 Pro and 250 Pro racers who finished the 2018 MTA World Two-Stroke Championship in April are given priority when in comes to being accepted to the 250/Open two-stroke class at the Giant RV Glen Helen National on May 26. After those riders, Glen Helen is looking for Pro riders (not racing the Glen Helen 250 or 450 National on that day), former AMA National riders and Loretta Lynn-speed Intermediates to fill out the available 40 spots. The Glen Helen race is not related to the 125cc series being conducted at other Nationals—this is the only two-stroke National class for 250cc and larger machines. Although lots of riders might think that they want to ride at an AMA National—think again. You need Pro speed and lots of two-stroke talent. This is not a track where you can roll the jumps or fail to clear the jumps. It will not be smooth, it will have big bumps, long ruts and factory rider-size whoops. So, think before you contact John Perry about entering the MTA-sponsored Pro Two-Stroke Challenge at (970) 559-0641 or email at email@example.com The post WANT TO RACE THE 250 PRO TWO-STROKE CHALLENGE AT THE GLEN HELEN NATIONAL? appeared first on Motocross Action Magazine.
Enjoy Adam Cianciarulo's complete segment from Premix 2. The post Adam Cianciarulo on a Two-Stroke Kawasaki KX125 appeared first on Transworld Motocross.
Join Mookie for a rip around Zaca Station. The post Malcolm Stewart on a Two-Stroke | GoPro On Board appeared first on Transworld Motocross.
THE GEAR: Jersey: FXR Clutch Retro, Pants: FXR Clutch Retro, Helmet: Shoei VFX-W, Goggles: EKS-S, Boots: Alpinestars Tech 7. Q: FIRST AND FOREMOST, IS THE 2018 YAMAHA YZ250 BETTER THAN THE 2017 YZ250? A: From a mechanical standpoint, no. But, if you are into blue rims, then yes. Q: WHAT CHANGES HAVE BEEN MADE TO THE 2018 YAMAHA YZ250? A: Yamaha changed the silver rims to black in 2016 and the black rims to blue for 2018. Of course, we can’t forget the BNG. In short, the YZ250 powerplant and rolling chassis are unchanged for 2018 (and largely unchanged since vice president Dick Cheney shot his buddy with a shotgun on a hunting trip back in 2006).The most amazing fact about the 2018 Yamaha YZ250 is that it is a 12-year-old machine that is still competitive long after its 2006 stablemates have faded into obscurity. Q: WHAT HAS YAMAHA CHANGED ON THE YZ250 OVER THE LAST 12 YEARS? A: We forgive you if you think that the YZ250 has been unchanged for the past 12 years, but that is closer to accurate than thinking that Yamaha has spent much in the way of R&D money on the YZ250 over the last 4,380 days. Still, we would be remiss if we didn’t correct the common assumption that Yamaha didn’t make any updates. Here is the list: Hand-me-downs. Unlike all the other Japanese manufacturers, Yamaha has continued to make two-stroke motocross bikes. That’s the good news. The bad news is that it has been pumping all its R&D money into four-stroke development, not two-stroke tech. And, while the YZ250 and YZ125 have not been completely ignored over the years, the best you could say about Yamaha’s glacial two-stroke R&D program is that it represents “benign neglect.” Every once in a blue moon Yamaha’s engineers will throw the two-strokes a bone, but it is almost always a hand-me-down part from the four-stroke line. SSS suspension. In 2006, Yamaha introduced Kayaba’s Speed Sensitive System (SSS). Twelve years later, it is still the best suspension on the track. It only has competition from the innovative WP AER air fork in 2018. We admire Yamaha for not jumping on the air suspension bandwagon. It took bravery not to be a copycat when the motocross world, not to mention Yamaha’s sales department, demanded PSF or SFF-TAC air forks. Yamaha’s test department held its ground on the coil-spring SSS forks and was proven correct, albeit 11 long years later. N3EW needle. Prior to 2007, if you hopped up a YZ250 it would ping. It couldn’t stand to run an aftermarket pipe, low-octane gas or be ridden hard in sand. In 2007, Yamaha’s engineers borrowed the needle that savvy YZ250 racers had been using and made it the stock needle. The N3EW needle delivered a big improvement in bottom-end and midrange response from the 38mm Keihin PWK carburetor. It should be mentioned that the 2018 YZ250 will still ping if you push it, pipe it or sand surf it. Removable bar mounts. Prior to 2008, the bar mounts were cast into the top triple clamp. Global spec. The 2011 YZ250 got the 75mm-longer Euro-spec silencer and the compression ratio was reduced from 10.9:1 to 10.6:1 (by increasing the volume of the combustion chamber by 0.5cc). These changes were implemented to allow one model of YZ250 to be sold worldwide. Before 2011, there were three different YZ models coming off the assembly line, with jetting specs, suspension settings, mufflers and cylinder head compression chosen for local Japanese, European and American tastes, fuel availability and sound regulations. Facelift. In 2015, Yamaha decided that after nine years of the YZ250 having the same body style, it deserved a facelift. Yamaha updated the styling of all the plastics, save for the front number plate and gas tank, to the “arrow” look of its four-strokes. Brakes. In 2017, Yamaha upsized the front brake rotor from 250mm to 270mm. Overview. Over the years, parts have been borrowed from the four-strokes and bolted onto the smokers. These parts include the rear brake caliper (2006), oversized 1 1/8th-inch handlebars (2007), smaller front-brake caliper and wave-style rotors (2008), a much smaller aluminum front-brake hose clamp (2009), white rear fender (2013), return to blue rear fender (2014), clutch lever position adjuster, Dunlop MX52 tires (2015), gold chain and black rims (2016), 270mm front brake rotor (2017) and blue rims (2018). The YZ250 was a middle-of-the-road handler in 2006, and it hasn’t gotten any better over the interim. Q: WHAT DOES THE 2018 YAMAHA YZ250 TWO-STROKE WEIGH? A: The YZ250 hits the scales at 219 pounds. That is light when compared to 450 four-strokes and some 250 four-strokes, but it isn’t light when compared to either the 2018 KTM 250SXF four-stroke at 218 pounds or the 2018 KTM 250SX two-stroke at 212 pounds. Q: WHAT DOES THE 2018 YAMAHA YZ250 TWO-STROKE COST? A: The 2018 YZ250 is the cheapest bike in the 250 class at $7399. The KTM 250SX retails for $500 more at $7899, and the Husqvarna TC250 at $7999. The basic problem for Yamaha is that without any significant mechanical changes over the last 12 years, most buyers buy a used YZ250 before considering a 2018 model. Yamaha fails to understand that the sales of brand-new YZ250s is damped by the fact that potential buyers can get an identical machine on the used-bike market for several thousand dollars less. Without a truly new product to offer, Yamaha is encouraging used bike sales. When you add in the fact that KTM continues to produce new, updated and high-tech two-strokes every couple years, buyers looking for the latest, greatest 250cc two-stroke will be going orange, not blue.It could use a stronger engine, more accurate frame, a diet and some loving care, but most MXA test riders love this bike as it sits. What updates did it get for 2018? Are you blind? The blue rims of course. Q: HOW DO THE 2018 YZ250 AND KTM 250SX COMPARE IN THE POWER DEPARTMENT? A: You might be surprised to learn that the peak horsepower difference between the Yamaha YZ250 and KTM 250SX is not that great. The KTM makes 47.20 horsepower, while the Yamaha YZ250 pumps out 46.08. But, it should be noted that the YZ250 hits its peak at a high 8800 rpm, while the 250SX hits its apex at 8200 rpm. When you add in the KTM’s 3 foot-pounds more torque at 500 rpm lower in the rpm range, the KTM engine is super responsive and effective. Remembering that peak horsepower is very similar, you might think that these two engines are also similar across the board. Nothing could be further from the truth. At 6000 rpm, the KTM makes 2 horses more than the Yamaha. At 7000 rpm, the KTM makes 4 horses more, and at 8000 rpm the KTM makes 2.6 horsepower more. Once the KTM 250SX peaks at 8200 rpm, it falls off quickly, and by the time the orange bike gets to the Yamaha’s 8800 rpm peak, the YZ250 is actually 4.7 horsepower to the good. It is this over-rev that makes the 2018 YZ250 competitive with the 2018 250SX. At roll-on and through the midrange, the KTM gaps the Yamaha by a big margin, which means that the YZ250 rider has to close the gap at the end of the straights. It makes for an interesting match-up—sheer grunt versus over-rev. Compared to the KTM 250SX, the YZ250 gives up 4 hp in the middle and 3 foot-pounds of torque, but makes it back on overrev. Q: IS THE 2018 YAMAHA YZ250 BETTER THAN THE 2018 KTM 250SX? A: No. The 2018 KTM 250SX weighs 7 pounds less, has incredible brakes, features a bulletproof hydraulic clutch, handles better, doesn’t vibrate (thanks to a counter-balancer), has a no-tools airbox (with a plug-in air filter), makes more power in the meat of the powerband, and is outfitted with Dunlop MX3S tires (instead of the YZ250’s old-school MX52s). In a direct comparison, the YZ250 weighs more, has weaker brakes, old-fashioned handling, considerable vibration and can’t hide its 12-year-old genes; however, what is amazing is that for a bike that was designed when “Malcolm in the Middle” was a hit TV show, the YZ250 is still a very good bike. Maybe it is not the purpose-built race bike that the KTM 250SX is, but it is a workman-like, all-around bike. Most MXA test riders love to ride the YZ250 two-stroke because it is “good enough.” It has good-enough power to be competitive in the right hands, good-enough handling to get around the track without incident (something that not every 2018 450 can claim), and good-enough ergos for Vet racers and professional practice riders. Amazingly, it is good enough that the majority of MXA test riders said that they believe that the Yamaha YZ250 is the most iconic motocross bike of the last 20 years. Without these forks, the YZ250 would have joined the CR250, KX250 and RM250 in the junkyard long ago. Q: WHAT’S SO ICONIC ABOUT THE YAMAHA YZ250? A: Make no mistake about it; motocross bikes are expendable, throw-away, obsolescence-prone machines that see their time in the sun come and go very quickly. To be iconic, a bike must have a purity of purpose that allows it to transcend time. It not only has to have been great when it was new, but it still has to be considered great a decade later. The acclaim must be almost universal, beyond reproach and, most difficult of all, virtuous. Think about that for a second. How many virtuous bikes can you think of? We aren’t talking about the latest and greatest models of 2018, as good as they are, for they have yet to stand the test of time. When polled, the MXA wrecking crew could only agree on two motocross bikes from the last 10 years that could be considered iconic, virtuous and beyond reproach—the 2008 Honda CRF450 and any year Yamaha YZ250 (starting in 2006 because of the introduction of Kayaba SSS suspension). And while we rate the 2008 CRF450 as a watershed bike, we probably wouldn’t line up to buy one today. But, we would gladly put our money down on a Yamaha YZ250. Q: WHAT DO WE THINK ABOUT THE YZ250 CHASSIS? A: To sum it up in one word, outdated. Don’t get us wrong; it does many things well and some things great, but the front end is shaky at speed and there has always been a touch of understeer in the aging frame. The KTM and Husky don’t have any handling issues; in fact, they are almost flawless. Luckily, you can Band-Aid the YZ250’s handling ailments by lowering the sag to 105mm, raising the forks into the clamps another 5mm, tightening up on the steering stem (to make a poor man’s steering damper) and throwing away the front Dunlop MX52 for a better front sneaker (like an MX3S). We add one tooth to the rear sprocket to help the YZ250 get to third gear sooner. Otherwise it lays down on exit. Q: HOW GOOD IS THE KAYABA SSS SUSPENSION? A: The Kayaba SSS components were 10 years ahead of the competition when they were introduced back in 2006. Kayaba SSS has held the mantel of the best showroom stock suspension for all this time. The SSS forks have superb bottoming resistance and very well-thought-out damping. They are among the best forks on the showroom floor today, but they can be improved. In stock trim, the Kayabas are busy and ride low in the stroke. Plus, the shock will blow through and wallow with a fast rider in the saddle. And while the new breed of rehashed coil-spring forks on the 2018 Suzuki RM-Z450, Honda CRF450 or the Kawasaki KX250F are not much of a threat to SSS dominance, that can’t be said for the Showa forks on the 2018 Honda CRF250 or the WP AER air forks on the Huskys and KTMs. They have caught up. Yamaha doesn’t need more top-end power, but it does need a boost of midrange to keep the KTM 250SX in sight. Q: WHAT DID WE HATE? A: The hate list: (1) Chassis. The YZ250’s chassis is old and outdated. It was always a middle-of-the-road handler and still is. It understeers and twitches unexpectedly at speed. Ultimately, Yamaha needs to dump some R&D money into its two-stroke department. (2) Engine. Love the powerband, but its Austrian competition will leave it in the dust off the start, up hills or in sand. (3) Front tire. Dunlop’s MX52 front tire makes the YZ250 front end feel worse than it actually is. Invest in a better front tire to get the full potential out of the YZ250’s aluminum frame. (4) Gear ratios. The upshift from second to third needs help. Luckily, once in third gear, no matter how far you rev the engine, it will never fall on its face. In a perfect world, we would like to see Yamaha move third gear closer to second (like Yamaha did on the YZ250X offroad version) and keep the same powerband. Q: WHAT DID WE LIKE? A: The like list: (1) Powerband. We think that more midrange horsepower would be helpful, but then so would more power everywhere. We love the YZ250’s power curve but need more oomph in the middle. (2) Suspension. The Kayaba SSS fork and shock are raceable right off the showroom floor—even though they are 12 years old. (3) Maintenance. It doesn’t take a mechanical genius to keep a YZ250 running. Changing a top end is cheap and easy compared to a four-stroke, made all the more affordable by the fact that you can do it yourself. (4) Bulletproof. The YZ250 is like the Energizer Bunny—it just keeps going and going. Q: WHAT DO WE REALLY THINK? A: We love this bike, not because it is the best 250 two-stroke on the showroom floors, but because it has been refined over a 12-year development period. Most of the bugs have been ironed out. It is a good, solid investment, proven by the big dollars that used YZ250s bring on the open market. We wish Yamaha had taken the reins and updated the YZ250 to help it reach its full potential. It didn’t. Yamaha stopped serious R&D 12 years ago. How great could it have been if Yamaha had cared. All the wishful thinking aside, the MXA wrecking crew applauds Yamaha for being the last Japanese manufacturer to build two-stroke motocross bikes—but we would prefer that Yamaha quit going through the motions and start playing the game as well as they did back in 2006. MXA’S 2018 YAMAHA YZ250 SETUP SPECS This is how we set up our 2018 Yamaha YZ250 for racing. We offer it as a guide to help you find your own sweet spot. KAYABA SSS FORK SETTINGS Yamaha did not give the 2018 YZ125 or YZ250 the latest version of its Kayaba SSS forks. They still come with the version with the smaller cartridge rod. No sweat. These year-old forks are perfect on the YZ250’s chassis. For hardcore racing, we ran this setup on the 2018 Yamaha YZ250 (stock clickers are in parentheses): Spring rate: 0.43 kg/mm Compression: 13 clicks out Rebound: 14 clicks out Fork-leg height: 5mm up (10mm up) Notes: These are awesome forks, made all the more terrific by the light feel and snappy input of the two-stroke engine. Obviously, if you are fast or fat, you might want to go stiffer on the fork springs. Typically, however, fast riders can dial in more compression (and use the crossover effect of rebound damping to get the stock fork springs to work). KAYABA SSS SHOCK SETTINGS For hardcore racing, we ran this setup on the 2018 Yamaha YZ250 (stock clickers are in parentheses): Spring rate: 4.7 kg/mm Race sag: 105mm Hi-compression: 1-3/4 turns out (1-1/2 turns out Lo-compression: 8 clicks out (13 clicks out) Rebound: 8 clicks out (12 clicks out) Notes: The YZ250 shock comes with a jumbo-sized 18mm shock shaft, Kashima-coated internals and SSS damping. AMA National-speed riders and heavyweight contenders will need to move up to a 5.0 kg/mm spring. YAMAHA YZ250 JETTING Here are MXA’s recommended jetting specs (when changed, stock specs are in parentheses): Main: 178 Pilot: 50 Needle: N3EW Clip: 2nd from top Air screw: 1 turn Notes: The 2018 YZ250 jetting is on the edge, albeit the good side of the edge. If you hop-up the YZ250 or add an aftermarket exhaust pipe, you will need to go to a bigger 180 main or add VP C-12 fuel in a ratio to your pump gas. Other than that, the YZ250 jetting is basic, simple and effective. The air screw is very sensitive from 1/2 turn to 1 turn out. The post MXA MOTOCROSS RACE TEST: 2018 YAMAHA YZ250 TWO-STROKE appeared first on Motocross Action Magazine.