When there was only one four-stroke on a track full of two-strokes back in 1996, it sounded kind of cool. But, that coolness waned when there were 40 four-strokes on the track and the thrum blended into a deafening roar. Now, all these years later, when there is only one two-stroke on a track full of four-strokes it sounds kind of cool. The world would sound better if we could fine tune the sound of a race by mixing two-strokes in with four-strokes so that the symphony sounded fortissimo. So, that this opportunity to listen the brass section—where the jets are seated. The post RAW HUSKY TC250 TWO-STROKE VIDEO: NO MUSIC EXCEPT WHAT YOU HEAR IN YOUR HELMET appeared first on Motocross Action Magazine.
This test of the 1999 Honda CR250 was featured in the August 1999 issue of MXA. This is everything you need to know about the 1999 Honda CR250. Below are 43 tips, fixes and ailments that you don’t want to live without when riding the first generation aluminum frame CR250. 1. Has your clutch lever come loose yet? Switch the stock pivot bolt nut to a locking nut replacement and blue Loctite it in place. The rear fender bolts also come loose. Do not use thread lock on the rear bolts because this can spin the nut embedded flush inside the plastic fender. 2. Check the spokes often. They get loose more than in the past because the suspension is better and the bike is being pushed harder through the bumps. 3. The chain adjuster and ignition cover bolts should also be checked before each ride. 4. When the tires are off, remove the rim strip and lubricate the spoke nipples with a wet anti-seize compound. Since the spokes require frequent tightening, it makes the nipples easier to turn. Clean the excess lube and run a strip of duct tape around the wheels a few times. 5. The bracket that holds the seat at the front of the tank comes loose. Check the bolts often. Do not Loctite the bolts since it will cause the nut that’s embedded in the tank plastic to spin loose. 6. Since the radiator shroud bolts are in a high maintenance area, grease those bolts to help keep the tank nuts locked in place. 7. Secure the sprocket bolts with red Loctite. Mickael Pichon on a factory 1999 Honda CR250. Many of these tips were applied to the factory Honda’s back then. 8. If you want to be factory, you will safety wire the throttle cable boots, front sprocket bolt, footpeg pins, steering stem nut, grips and brake house joints. 9. If you don’t put the front wheel in the fork properly it will bind fork movement. Do not tighten the axle by turning the right side nut. Keep the axle nut fully seated and secured by the right fork leg axle pinch bolts. Turn the axle from the left to tighten. Leave the left side axle pinch bolts loose and lightly insert a small screwdriver between the axle split to relieve its clamp on the axle. Pump the forks a few times and, while keeping a load on the fork, remove the screwdriver and tighten the pinch bolts. Re-lube the pivots on a 1-1/2- to 6-month service schedule. 10. The suspension hot-rod shops advise servicing the fork and shock after the first five hours of riding. 11. To find a degree of fork plushness, first remove the springs and measure their overall length. Some springs have been coming up on the short end of the scale, so use spacers to bring the overall measurement to 495mm. Only use steel preload spacers available from a suspension shop. 12. Fill each leg with 378cc’s of Showa SS7. Avoid Honda’s HP oil, which measures as a 7-weight. (Showa SS7 is a lighter 5-weight oil.) Too Tech Suspension runs an ultra-light 3-weight shock oil. 13. An easy way to change oil height without using oil is to make fork oil displacers. Cut six, 25mm-long sections of one-inch diameter, schedule-40 PVC pipe. Cut a lengthwise split in every section. On each fork leg position three PVC pieces on the cartridge rod over the spring seat. When you displace the fork fluid, the oil level is raised and the air space reduced. Each spacer reduces the air space by 5cc, which makes the action more progressive at the end of the stroke. This allows the damping adjusters to be run more open for smoother action and the bike to hold its head up better. 14. For the best overall feel, lower the front by raising the legs 2mm to 3mm up in the clamps. Adjust the forks 12-clicks out on compression and 13 out on rebound. After riding, remove the PVC fluid displacers as necessary to achieve smooth bottoming performance. Most racers run two spacers per leg, while heavier, sumo riders run three. 15. Honda uses chain torque to help the suspension resist bottoming. The way it works is that when the rear suspension collapses, the chain touches the top chain roller. Under power, the top length of chain is taut and it pushes against the top roller, thus helping to fight bottoming. Unfortunately, we think that Honda runs the wrong chain geometry on the CR250. MXA fixes it by running a smaller CR80 chain roller at the top. Now take the original top roller and switch it with the larger-diameter bottom roller. With the chain geometry back in line, it’s crucial to run exactly 25mm to 35mm of chain slack, measured just behind the back of the swingarm’s top chain slider. Back in 1999 Kevin Windham rode for factory Honda aboard a CR250. 16. Changing the gearing can throw the chain geometry completely out of whack. While lower gearing will provide smoother power delivery and pull longer between gears, don’t just run a rear sprocket with more teeth. Honda technicians claim that you can improve the chain line and suspension action by using the CR500’s 14-tooth countershaft and CR125‘s 51-tooth rear sprocket (13/50 stock). 17. With progressive fork action and smoother shock action, it is possible to run more shock preload. Adjust a 98mm ride height, five to six-out on compression, three-turns out on high-speed compression and 12 to 13-out on rebound. Cumulatively, these mods make the rear suspension less sensitive to power forces and softer through hard, square-edged acceleration bumps. The balance will also be much more consistent in turns. 18. Watch the swingarm and chain guide pads. If the chain guide pad wears too far, the chain saws through the guide. Worn swingarm pads will alter chain adjustment and the chain torque’s suspension effect. 19. Your bike comes stock with a chintzy chain. Honda recommends the $100 DID gold chain. It lasts four times longer and seldom requires adjustment. We liked the stock gearing on the 199 CR250. 20. Apply anti-seize to the chain adjuster bolts. When the bolts lose their factory coating, the threads seize and will effectively ruin the swingarm. Throw out the stock nuts and use self-locking replacements. Team FMF says to keep an eye on the swingarm bolts. They bend. 21. For jetting MXA recommends a 172 main, 55 pilot, 1370L needle in the 4th clip and air screw two-turns out. If you need richer response through the midrange, switch to the 1369 needle in the fifth clip. Pro Circuit runs a leaner 168 main, 55 pilot, 1370 needle in the leaner 3rd clip, air screw at 1-1/2 turns out and race gas. 22. Team FMF suggests that the air boot to airbox mount be removed and thoroughly sealed with silicone. 23. Tape the carb vent hoses together and route out near the shock linkage. 24. The kill switch wire pulls taut when turning the bars to the left and can get smashed between the stops turning to the right. Planet Honda protects its kill switch wire with a spiral wrap and reroutes it through the frame behind the steerer tube. 25. The actuating cam on the clutch release lever can be chamfered for easier clutch feel. Planet Honda also polishes the clutch rod for smoother pull. Where the clutch cable makes its sharp 90 degree turn, use a zip-tie and secure it to the front number plate. This reduces cable flex and improves clutch feel. Finally, use a light machine oil to lubricate the cable. 26. Check the throttle cable when running a bar that is taller or wider. Turn the bars from lock to lock and see if the cable is pulled taught or if it bunches up. Carefully reroute as required. 27. An aluminum throttle tube rotates easier on the bar and provides smoother throttle action. 28. Even though the ’99 CR250 handlebar is rubber-mounted the vault-like aluminum chassis transfers excessive vibration to the grips. Use an aluminum bar and run a bar snake damper. Frequently check the perch torque. 29. Here is a super secret frame trick. Remove the triple clamp and fill each frame spar by shooting spray insulation foam through the relief hole inside the steerer tube. When the foam dries, cut off the excess and reinstall the clamps. This will reduce vibration. 30. Run clear adhesive on the plated footpeg area of the frame, airbox and side plates. This keeps boot-wear induced aluminum oxide from ruining the look of the bike. 31. Trim the radiator shrouds where they rub against the frame. 32. Check the piston ring end gap when servicing the top end. The optimum measurement is .015 inches and a tight ring can be filed to the proper gap if necessary. Use a fine file to lightly chamfer the edge of a new piston skirt. 33. The power valve linkage is often misaligned when the cylinder is reinstalled. Visually check that the pin in the case lines up with the fork in the cylinder. The valve is under spring preload and it is often necessary to counter the tension to line the fork over the pin. 34. Frequently remove the right side power valve cover and check the condition of the valves and linkage. Rotate the valves by hand and feel to see if they are sticky. Although contact cleaner dispels oil residue, it cannot not remove built-up varnish. 35. Frequently check the reeds for cracks and chips. Most race teams use the stock petals, but they wear out quickly. If you are looking for more durability, Team FMF suggests running an aftermarket carbon replacement and Planet Honda says they’ve had some success with Boyesen fiberglass replacements. 36. There is a nook up inside the front of the rear brake caliper hydraulics that likes to trap air. Unbolt the caliper and hold it upright in the air when bleeding the brakes. Pry the pads apart and remount the caliper. Bleed the front and rear brakes often if you are a crasher. (It’s possible for air to mix throughout the hydraulics as the bike cartwheels down the track.) Sebastien Tortelli on a factory 1999 Honda CR250. 37. Planet Honda replaces the stock triple-clamp mounted front brake hose guide with a number plate-mounted guide from IMS. They claim much improved hose movement. 38. Honda’s aluminum clutch drive plates quickly contaminate the gearbox oil (requiring the oil to be changed after each ride). Honda recommends their own GN4 10/40 oil, but any quality 10/40 motor oil will do. 39. Team FMF says that the stock tire tubes are thin and should be switched out with regular Dunlop replacement tubes. The stock tubes don’t hold air very well, so check tire pressure before each ride. 40. Cut 20mm lengths of hi-temp hose with an ID that snuggly fits over the exhaust springs. Use contact cleaner to slip the hose on the spring. This cuts down on vibration. Loctite and keep an eye on the pipe bolts. Since this is a high-maintenance area, don’t use anything stronger than blue thread lock. 41. Run four exhaust spacers between the pipe and manifold (#18309-K23-600). The increased head pipe length makes delivery noticeably torquier off the bottom. 42. Change to a metal ACG cover (that’s is Honda tech speak for an aluminum ignition cover.) Although the metal cover seals better than the stock plastic unit, still take it off after each wash, spray the innards with WD40 and keep the cover off until the next ride. 43. If your track runs an Open class, RPM’s 285 kit gives a six horse boost throughout the range with much improved over rev. It runs $750. The post TWO-STROKE TUESDAY | INSIDE SECRETS OF THE 1999 HONDA CR250 appeared first on Motocross Action Magazine.
2018 SOUTHWICK MOTOCROSS | COMPLETE COVERAGE Throughout the outdoor season, Dubach Racing Development owner and operator Doug Dubach has been hard at work training the 2017 Japanese National Motocross Champion Yusuke Watanabe during the week and traveling with the #101 to each round of the Lucas Oil Pro Motocross Series. This weekend at the 2018 The post The Dubachs Take On Southwick appeared first on Transworld Motocross.
The 2006 Suzuki RM125 in action. This article is from an archived issue of MXA. This just might be the last year of the 125cc two-stroke (at least in terms of the little two-strokes receiving any mods beyond BNG). How can we say such a thing? That’s simple! Kawasaki decided not to bring the 2006 KX125 to the United States, and Honda made only one change to the CR125 for 2006 the radiator sticker (and to be honest, you can barely tell they did that). Yet, amid all the doom-and-gloom for tiddlers, there are a few bright spots and Suzuki’s RM125 is one of them. So how did Suzuki separate themselves from the dying herd? They made improvements to the RM125. Which, shockingly, is something that they were unable to do to the better-selling RM-Z250. We like to think that Suzuki’s engineers knew they could make the RM125 better, and rather than take the easy and cheap way out, they did right by their customers. They set aside R&D time and seed money to make the 2006 RM125 better than the 2005 model. Kudos. Q: WHAT EXACTLY DID SUZUKI CHANGE ON THE 2006 RM125? A: They fine tuned it. They increased the diameter of the piston ring knock pin, made the reed valve intake passage narrower, reshaped the exhaust chamber, created a new CDI ignition map and put Renthal Fatbars on it. Q: WHAT DO THESE MODS MEAN ON THE TRACK? A: Unfortunately, not a whole lot. The engine is still a mid-and-up maven. Don’t waste your time trying to lug it down low. It doesn’t pull hard down low like a 250cc four-stroke, or YZ125, or even the MIA KX125. To make the most of the RM125’s power profile, the best strategy is to fan the clutch on the exit of every corner. Oh yeah, make sure the throttle is wide open. You have to keep the RM up in the rev range. If you can do this, the engine is competitive and will work with you. Fall off the pipe and you start from scratch. To make the most of the RM125’s power profile, the best strategy is to fan the clutch on the exit of every corner. Q: IS THE 2006 RM125 FASTER THAN THE 2005 MODEL? A: Yes. Is it a lot faster? No. If you were expecting the RM125 to magically become a weapon of mass destruction against 250 four-strokes, you will be sorely disappointed. The 2006 RM125 is a great entry-level 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: HOW GOOD IS THE SHOWA SUSPENSION? A: Much improved. Over the last few model years, the MXA wrecking crew has complained about how soft the RM125 suspension was. Suzuki listened. The 2006 RM125 features much more realistic suspension for the average motocross racer. Finally, it has some versatility for a wide range of riders not just mini refugees. It can still be set up on the soft side for lightweights (by taking most of the compression out in both the forks and shock), but it comes from the factory set up stiff enough to handle normal-size riders. How did Suzuki accomplish this feat? They stiffened up the valving on the forks and actually went to a stiffer spring rate on the shock. Forks: If it were us, we’d opt for the stiffer 0.43kg/mm front fork springs. This is a necessary mod for most Intermediate and Pro racers, as well as heavier riders. The stiffer springs make the forks ride up higher in their stroke and just give the bike an overall better feel. To complement the stiffer fork springs, we chose to set the compression and rebound clickers at ten out. Shock: On the shock, we set the sag at 98mm and turned the compression to 12 out with the rebound set at ten out. We opted for the stiffer 0.43kg/mm front fork springs. Q: HOW DOES THE RM125 HANDLE? A:Cornering has always been a Suzuki strong point, but high-speed stability has been its weak link. As it sits, the 2006 RM125 is a cornering fool. It loves to dive inside. Its second best trait is air time. This bike lives to jump. It feels well balanced in the air. It’s a little busy at speed, but because the bike feels light, the suspension is stiffer and the balance is better, it’s not scary. Q: WHAT DID WE HATE? A:The hate list: (1) Power: It’s good for a 125, but not as good as the YZ125 or KTM 125SX. If we were to throw all the 250Fs in the mix, that leaves the RM125 eighth on the list. Q:WHAT DID WE LIKE? A:The like list: (1) Handlebars: Last year Suzuki had cheap knockoff aluminum handlebars. This year they got official oversized Renthal Fatbars. That’s one heck of an improvement. (2) Power: We know it was on the hate list, but we like the way the RM125 engine runs. It’s exciting. Hold this bad boy wide open, fan the clutch and listen to the engine sing. You’ll be living on the edge, but sometimes that’s the only thing that makes life worthwhile. (3) Controls. It just feels like all the controls on the RM125 are in the right place. The clutch perch is perfect, it stops on a dime, and it shifts with ease. Q:WHAT DO WE REALLY THINK? A: It’s hard not to like the RM125. Unfortunately, we all must come to the realization that it’s not really competitive in the 125 class against 250 four-strokes anymore (and even if it was, it’s not the best 125 two-stroke choice either). But it is a vastly improved 125 that deserves to spend time racing around a motocross track. The post ON RECORD | WE TEST THE 2006 SUZUKI RM125 TWO-STROKE appeared first on Motocross Action Magazine.
This test of the 2004 Kawasaki KX125 was featured in the November issue of MXA. We hate to burst anyone’s bubble, but Ryno Hughes, Grant Langston, Mike Brown, Brock Sellards and Branden Jessemen should count their lucky stars that James Stewart is on a 2003 Kawasaki KX125 instead of a 2004 model. Not that Bubba seems to need any help, but the ’04 KX125 has taken a quantum leap forward over the bike James is riding now. How so? On the dyno, it pumps out close to 35 horses. Last year it didn’t break 32. That’s huge. More like incredible! Okay, Stewart doesn’t need any help, he’s waxing, polishing and buffing the competition on his 2003, but wouldn’t you like a little help? Thought so. James Stewart was head over heals faster than the competition in 2004 on his KX125. The question at hand for the MXA wrecking crew was whether the KX125’s sudden reversal of fortune in the dyno room translates to the race track. We’ve seen a lot of dyno queens that couldn’t get out of their own way when the rubber met the road. Where would the 2004 KX125 fall? Dyno queen or duke of dirt? Q: CAN A KAWASAKI KX125 ACTUALLY MAKE 35 HORSEPOWER? A: Kawasaki‘s sudden surge on the dyno is impressive, but where did it come from. Last year MXA had a full-race KX125 that made the same numbers as the stock 2004 KX, but it was ported, piped, milled and fueled (with $8 a gallon race gas). For 2004 we got the same numbers off the showroom floor (using $2 a gallon 91 octane pump gas). The 2004 KX125 engine produced there more ponies than the 2003 engine. It was a huge improvement. Factory 125’s, like the one that James Stewart rides, make a lot more than 35 horses, so for a stocker to hit that number isn’t out of the realm of possibility. But, the only other stock two-stroke in that range is the KTM 125SX. Q: HOW DID KAWASAKI PULL 35 HORSEPOWER OUT OF THEIR HAT? A: They made seven changes to the 2004 KX125: (1) The compression was raised. For 2004 it’s 8.5 to 11.1:1. More compression typically means more power. (2) The exhaust port was reshaped to improve overall flow. (3) The gap between the power valves was reduced for better sealing, especially when the valves are in the fully closed position at the exhaust port. (4) The exhaust pipe is all-new from the head pipe back. (5) Internal pressure on the piston ring has been reduced to lessen friction and allow for a freer rev. (6) The carburetor’s air intake manifold is shorter and straighter. (7) The angle of the reeds was changed from 90 degrees to 45 degrees and the reeds themselves are shorter and a secondary stepped reed is used for auxiliary boost. Q: WHAT IS THE BIGGEST CONTRIBUTOR TO THE KX’S POWER ENHANCEMENT? A: The pipe accounts for the biggest chunk of the power gain, but engine dynamics are a cooperative effort. Every little mod has to work in conjunction with the next. Kawasaki obviously got it right. Q: IS IT A DYNO QUEEN OR DUKE OF DIRT? A: It is very good. Given that we were overly optimistic after the dyno runs, it would be hard for any engine to live up to the hype. The KX125 powerband is exactly where you would want a 125 to be. It makes good power down low and then really starts pulling through the middle (and revs out far enough to get you to the next corner). The 2004 KX125 powerband is exactly where you would want a 125 to be. It did have a few weird traits. (1) Every test rider felt that the engine revved slowly. It didn’t want to scream. It growled in a deep roar. (2) Given it’s horsepower advantage over the RM125 and YZ125 (which make 33 horsepower on the same dyno), the KX125 didn’t seem to have a leg up on them. It didn’t give any ground, it just didn’t display a two horsepower advantage over its weaker opponents (conversely, the 34.5 horsepower KTM 125SX did). Queen or Duke? It’s a push, but it is a better engine than last year and gives up nothing to its red, yellow and blue competition in the dirt. Q: IS THERE ANY ADVANTAGE TO BE FOUND IN A GEARING CHANGE? A: Yes, but with a caveat. Intermediates and Pros can get away with the stock gearing. But Novices and Beginners will definitely need to add a tooth. In all honesty, Intermediates and Pros should try one tooth on the rear also–especially on tight tracks. The extra tooth takes the work out of keeping the revs in the meat of the powerband (and bike out of first gear). Novices and Beginners will definitely need to add a tooth in the rear. Q: WHAT ABOUT THE KAYABA SUSPENSION? A: Off the showroom floor it feels very unbalanced. The first test rider was back in the pits after one lap to stabilize the front/rear bias. In stock trim the 2004 KX125 has a nasty stinkbug feel. The front rides low and the rear is really high. Forks: Surprisingly, the low rider front end has nothing to do with the fork springs. We liked the spring rates, valving or clicker settings. The culprit? For some reason Kawasaki specs their bikes with the fork tubes slid way up in the top triple clamps. We’re talking freakishly high. We slid them down until only 5mm of fork leg protruded above the triple clamp. This was a quick and free fix. As we said, we liked the fork set-up. The stock compression and rebound clicker settings are in the ballpark for most riders, although faster or heavier riders will need to turn the compression in a couple of clicks. If you are light do the opposite. Shock: Yamaha-style rear shock linkage is en vogue for ’04. Both Suzuki and Kawasaki have adopted the Yamaha method of mounting the linkage to the swingarm instead of the frame. The new mounting location reduces thrust loads on the frame and shock and allows Kawasaki to us a 20mm longer shock and 17mm longer swingarm. The longer swingram is not all that new; the Pro Circuit team has used the longer KX250 swingarm on their 125 National bikes for several years. How does it feel? Stiff, with its 4.9 kg/mm shock spring the KX125 rear shock will be able to handle riders in the 200 pound range. At first we were tempted to toss the shock spring in favor of something softer, but something told us that the shock was over damped, not over sprung (at least or our test rider’s weight). What was our solution? We lowered the race sag to 102mm to drop the shock a little farther into its stroke. And, then we began to progressively do laps and turn the compression clicker as we went. We stopped when the shock stopped kicking. The magic number for us was 14 clicks out on compression. Q: WHAT DID WE HATE? A: The hate list: (1) Balance: We hope that your friendly local Kawasaki dealer will rectify the fork height problems on the showroom floor. If he doesn’t you can fix the feel with a 10mm T-handle. (2) Handlebars: KTM’s and Honda’s aluminum bars make the KX’s steel bars look archaic. Are you listening Yamaha and Suzuki? (3) Shock: If you are a mini transplant, pushing 125 pounds soaking wet, you are going to find the rear of the KX too stiff. You will have to punt it to a suspension shop. (4) Ergonomics: Maybe it’s just us, but the KX125’s ergonomics are best suited to jockeys. This is the Seabiscuit of motocross ergos. (5) Clutch perch: What, no quick-adjust? No on-the-fly whirlygig? Everyone else has one. Why don’t they? (6) Gas tank: We don’t like black gas tanks. Never will. You can’t tell if it’s full until the ground is wet. Q: WHAT DID WE LIKE? A: The like list: (1) Power: The bike puts out some serious ponies and does it in a distinctive way. The extra power may not always come to the forefront, but its always there–working like an invisible hand to urge the KX on. (2) Front brake: Honda front brake patent is up and Kawasaki has Honda-style brake line routing and a more powerful brake because of it. (3) Triple clamp: It took a long time for Kawasaki to put a rubber-mounted triple clamp on their 125, but they did and with its two-bar positions we love it. Q: WHAT DO WE REALLY THINK? A: Last year the MXA wrecking crew discounted the Kawasaki KX125. We denigrated it by calling it “YZ125-lite.” No more. For 2004 the KX125 will not take a back seat to anyone in the horsepower department. This is not the “Lite” version of a 125. It’s got a full figure at last. The post TWO-STROKE TUESDAY | WE TEST THE 2004 KAWASAKI KX125 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. (6) PDS suspension is five pounds lighter than linkage suspension. 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 damping 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 1999 – hands-down. But, they are gone for 2000, 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 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 ON RECORD | WE TEST THE 2000 KTM 250SX TWO-STROKE appeared first on Motocross Action Magazine.
Seven-time British National Motocross champion Kurt Nicoll reveals the machine he’ll race at the Tenth Anniversary Vets des Nations at Farleigh Castle in September – a fully restored replica of his 1992 KTM 500 factory racer. He rides the bike and talks about the machine and his hopes for the VMXdN this year for motoheadmag.com. The post KURT NICOLL UNVEILS THE 1992 KTM 500 TWO-STROKE HE PLANS TO RACE AT THE VET MXDN appeared first on Motocross Action Magazine.
This article of the 1999 Kawasaki KX250 was featured in the 1999 August issue of MXA. HERE ARE 40 INSIDE SECRETS OF THE 1999 KAWASAKI KX250 1. When changing your tires, throw away the rubber band that covers the spokes. Use a roll of duct tape to put a one inch strip of tape around the rim three layers thick. The tape does a much better job buffering the tube from the spoke heads. It also keeps pressure on the nipples and helps prevent loosening. 2. When you replace a spoke, first apply Bel-Ray Assembly Lube to the threads before threading the nipple. It keeps the fragile aluminum nipple from corroding and becoming impossible to turn. The spokes next to the rim locks come loose first. 3. Do not over tighten the aluminum spoke nipples. Only snug them so they will have a little give to better handle extreme G-forces. 4. When installing a new tire, apply baby powder to the tube. This will allow the tube to flex freely in the tire without chafing. 5. Do not spray any kind of lubricant or cleaner on your disc brakes when cleaning the KX250 . Even after changing a tire, clean the disc with contact cleaner to remove any over spray that might have gotten on the disc from lubricating the bead or manhandling the wheel. 6. You can not bleed KX brakes too often. Make it part of your weekly maintenance regimen. There have been reports of rear brake O-ring failures, so keep an eye out for leaks at the rear caliper. 7. Kawasaki brakes are moderately good at best. Do what the factory does and run oversized rotors front and rear (they use Braking). Braking‘s rotors measure 260mm and 230mm relative to the stock 250mm and 220mm sizes. It will still be necessary to bleed the brakes after every ride (or once a month for casual riders). It’s best to completely flush out the standard DOT-5 fluid with Motul. 8. One of the better ways to service the hydraulics is to push a clear, 3/16-inch hose on the bleed nipple so that it forms a sharp loop before hanging the end of the hose in a jar. Pump the brake a few times, and while holding it in, crack the bleed fitting. Pull the lever to the bar. Close the bleed and release the lever. Repeat this until the fluid makes its way around the loop and starts to drip out the end of the hose. Since the filled loop will keep air from backtracking into the system, it is possible to leave the bleed open (once the loop is full) and to pump the lever while feeding fresh fluid into the master cylinder. Continue this until fresh fluid with no air bubbles is visible through the first half of the loop in the hose. Servicing the rear brake is just like servicing the front except you are pushing down on a pedal instead of pulling in a lever. 9. Do you want arm pump-free clutch and throttle action? Kawasaki technicians use a Motion Pro Cable Luber. First flush the cable with contact cleaner. Follow that with a dousing of Tri-Flow. Remove the carburetor cap and hang the cap and slide off to the side when lubing the throttle cable. 10. Most riders, especially those over 5′ 9″, turn their bottom bar clamps around to move the bars farther forward. Do not turn the top clamp around, though. 11. The stock handlebar bend is awkward for some riders. Switch to anything other than the stock KX-bend. When installing aluminum handlebars, first chamfer the clamps so the sharp edges won’t cut into the aluminum. 12. There are directional clamps on the front master cylinder and the handlebars. The handlebar top clamp has to have the side with the diagonal cut put towards the gas tank. Tighten the front two bolts first so there is no gap between the top and bottom clamps. Then tighten the rear bolts to the specified torque. The front master cylinder clamp has an arrow that should point up. Tighten the top clamp bolt until there is no gap between the two pieces. Then tighten the bottom clamp to the specified torque. 13. Use hi-temp silicone to seal the exhaust pipe to the cylinder. This will help cut down on pipe vibration. 14. Disassemble the airboot to airbox clamp and silicone the sealing edges before reassembly. 15. When washing your KX250, cover the air filter with a plastic bag. If you get water on the filter and then start the bike, it can suck water through the filter and into the top end. 16. Thoroughly oil the filter before squeezing out the excess. Only put a light layer of grease on the filter sealing lip. Before racing, start the bike up and let it run for a couple of minutes. This eliminates any richness from the fresh oil. 17. Apply a bead of silicone to the clip of the counter sprocket. This keeps dirt from getting down the spline and compromising the clip seat 18. When tightening the rear axle, put a rag or old wrench between the chain and the rear sprocket. Roll the wheel backwards until the chain pushes the wheel forward against the adjuster bolts. This eliminates the chance of tightening the wheel when the adjuster bolts aren’t seated. 19. The KX250’s upper chain roller has a tendency to fall off. Use thread lock. 20. Team Green uses a 50/50 mix of Bel-Ray Waterproof Grease and Bel-Ray Assembly Lube to lubricate all pivots. The blend makes a great bearing lubricant that won’t wash out. 21. At high altitude switch to Kawasaki’s optional 1.6 radiator cap. It holds the increased pressure this environment creates on the cooling system. 22. Team FMF recommends checking the head stud torque every time the top end is removed. 23. Rick Peterson makes a 285cc kit that needs to be considered for Vet or Open class action. In the standard tune, expect a six horsepower boost with a more drawn-out spread. 24. Team Pro Circuit tightens the front wheel by spinning the axle and holding the nut. They claim that tightening the nut will give a false torque reading and possibly bind the forks. 25. Grease the shroud tank bolts so they don’t seize in the brass nuts embossed into the tank plastic. 26. For jetting the MXA test crew runs a 158 main, N3WK needle (in the third clip), 45 pilot, 58 power jet and air screw 1-3/4 turns out. 27. Team FMF recommends breaking the engine in with the stock brass before jetting leaner. FMF’s sea-level jetting recommendation is a 155 main, N3WK needle in the third clip, 45 pilot, 60 power jet and the air screw 1-1/2 to 2 turns out. This jetting is run with a 50/50 mix of pump and VP Racing fuel. 28. Fork performance is mediocre. Here are four quick fixes: (1) First, raise the legs up no more than 10mm in the triple clamps for tighter steering. (2) Switch from the stock progressive rate spring to a straight-rate 0.44kg/mm spring. (3) Go ride and tune out bottoming by raising the oil height in 5mm increments. The stock oil height is 105mm. (4) Turn compression to 10 out and rebound to 11 out as starting points. 29. Install the forks in the triple clamps so that the left fork has the bleed screw at 10 o’clock and the right screw is at the 2:00 o’clock position (When sitting on the bike). This allows the easy access to the screws. 30. After the fork tubes are repositioned, it will be necessary to realign the fork protector guides. Always make sure there is a gap on the inside or the guide will cut the protector. 31. Frequently torque the rear suspension rocker arm where it bolts to the frame. When this bolt is loose there will be some play at the beginning of the suspension movement. Move the rear wheel up and down when the bike is on a stand to see if you can feel the looseness. 32. Inspect and re-grease the lower shock mount every two to three rides. This pivot doesn’t seal well and its low-to-the-ground position makes it very susceptible to dirt contamination. 33. Set race sag between 98mm and 100mm. Adjust low-speed compression eight clicks out, hi-speed compression full soft and rebound at 12 out. Riders over 165 pounds should use a straight-rate 5.3kg/mm spring (or Kawasaki’s optional heavy progressive-rate spring). The heavy optional Kawasaki spring measures 5.0/5.3/5.5, while the stock spring rates at 4.8/5.1/53. 34. Kawasaki’s rear seat bracket rivets will either break or pull through the plastic base. Drill out the rivets and replace them with 3/16″ stainless steel rivets. Use a washer on the back side so the rivets can’t pull through the seat base. 35. The keyhole slot that locks the front of the seat to the gas tank will oval out and pull off the tank bolt. Dirt Squirt Products sells a carbon insert that fits under the foam and over the original key hole. This carbon fiber insert is used by team Kawasaki and Team SplitFire. 36. Keep an eye on the piston skirt for scuff marks (caused by the two intake port bridges). Only replace the piston if you can feel the scuffs when dragging a finger nail across the skirt. 37. Most riders swap the stock 48-tooth sprocket for a lower 49- or 50-tooth rear sprocket. 38. Invest in a spare set of clutch plates. The clutch is weak and will quickly fail under heavy abuse. The quick fix is to run stiffer KX500 springs. Some riders have had success replacing the aluminum with steel plates. The steels will handle more abuse and won’t dirty the oil as quickly. The ultimate fix is a Hinson clutch basket. 39. If you have your cases split, take the opportunity to remove the shift drum and use a Scotch-Brite wheel to polish the slots that the shift forks ride in. This makes it easier for the fork to move and improves shifting. 40. Every time the clutch is serviced, remove the shift shaft and inspect the pawl change lever. Look for indentations on both sides of the lever where it contacts the shift star. If let go, the indentations can catch a star pin and hang up the shifting. Smooth out the indentations with a fine file. The post TWO-STROKE TUESDAY | 40 INSIDE SECRETS OF THE 1999 KX250 appeared first on Motocross Action Magazine.
document.createElement('video'); https://motocrossactionmag.com/wp-content/uploads/2018/06/Rad_Valve_Main_.mp4 Virginia rider Ryan Smith raced the two-stroke race in Muddy Creek in jeans and a long sleeve t-shirt. Ryan placed 10th. This was the second annual Cody Gragg Memorial two-stroke race that went on during the fifth round of the AMA outdoor National series in Muddy Creek. The day before the National on Friday, there was a two-stroke qualifier as there were two divisions of smokers lined up. Last year the pro purse was up to $14,000. This year is was just over $10,000. Not bad for an amateur race. That is more money than most the pros would make on a race weekend. The tradition was started in 2017 when Cody Gragg and his father Chris were in a fatal accident on their way to a race. This annual event at Muddy Creek Raceway will carry on their memory and will be an annual tradition at Muddy Creek. TWO-STROKE RACE RESULTS (TOP TEN) Ezra Hastings (KTM)–$3000 +$500 holeshot bonus Jyire Mitchell (Hon)–$2000 Justin Rodbell (Yam)–$1500 Luke Neese (Yam)–$1000 Hayden Hefner (KTM)–$700 Blake Taylor (KTM)–$500 Sean Cunningham (KTM)–$400 Harrison West (Yam)–$300 Carter Biese (KTM)–$200 Ryan Smith (Yam)–$100 2018 MUDDY CREEK NATIONAL | FULL COVERAGE Nate Thrasher decided to race a 125cc machine in a sea of 250s. Nate placed 12th. Alex Wagers (left) and John Bowlin (right) battle it out. Blake Taylor finished 6th on his YZ250. Luke Neese made a 1000 bones for placing 4th. Brent Duffe’s Honda CR250 looks like a factory smoker. Austin Kimsey on his CR250. Austin Johnson. Tj Snow on a YZ250. Third place went to Justin Rodbell. Jack Beeland. Patrick Jackson. Kyle McElrath on a Honda CR250. Cameron Pappas got off to a good start. TWO-STROKE ALL-STAR RACES | FULL COVERAGE Photos by Brian Converse The post 2018 MUDDY CREEK NATIONAL | $10,000 TWO-STROKE RACE appeared first on Motocross Action Magazine.
2018 MUDDY CREEK NATIONAL | FULL COVERAGE Ryan Sipes has been racing the National circuit since 2004. His best overall result was 3rd in the 250 East Coast Supercross series in 2011. A few years ago, Ryan switched disciplines to the offroad racing world. He hasn’t forgot about his roots as he makes sure to hit a few outdoor Nationals each yearl. He usually rides the 450 class, but this year he wanted to try to qualify on a 125cc machine in the 250 class at the 2018 Muddy Creek National. With the top 36 qualifying straight out of practice, Ryan qualified 25th out of 71 riders. Check out Ryan ripping around of the Husky TC125 two-stroke in practice at the 2018 Muddy Creek National. Maybe he will be able to score some points today! The post RYAN SIPES QUALIFIES ON A 125cc IN MUDDY CREEK | LISTEN TO THE TWO-STROKE SING appeared first on Motocross Action Magazine.