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Dirt and Trail July 2018 issue 2

  • Text
  • Durability
  • Bikes
  • Riders
  • Suspension
  • Enduro
  • Motorcycles
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  • Clutch
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“The sound of that 150

“The sound of that 150 in the hills is quite something…. I love the smell of two stroke in the morning!” 20 DIRT & TRAIL MAGAZINE JULY 2018

The 2019 four strokes use the KTMdeveloped DDS clutch (damped diaphragm steel) with a wear-free steel basket and extremely heat resistant clutch plates. This design employs a diaphragm spring (Belleville washer) instead of the usual coil springs, which makes for a considerably easier clutch action. The diaphragm spring also leaves sufficient space for a rubber damping system integrated into the clutch hub, which benefits for both traction and durability. Formula 1 supplier Pankl now makes the five-speed transmissions on the 2019 KTMs. All four-stroke engines are fitted with a gear sensor giving the option of different engine characteristics for each gear. All the four strokes feature Keihin Engine Management System, with electronic fuel injection, features a new 44mm throttle body, reworked throttle cable mount, and improved seal of the Manifold-Absolute- Pressure (MAP) sensor makes the system more reliable. The ECU features new maps adapted to the new exhaust and cylinder head and it regulates the unique traction and launch control. In addition it provides different maps for optimal power characteristics for each gear. 2019 KTM 250SXF, 350SXF & 450SXF wheels/battery/wiring harness 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 tightening the spokes. The tyres are a Dunlop Geomax MX3S combo. 250SXF, 350SXF and 450SXF fourstrokes get new lightweight, 2 Ah, Lithium- Ion (lithium-iron-phosphate) starter battery that contribute to the low weight. A reworked packaging of the voltage regulator and condenser concentrate the electrical components in a tray below the seat and makes the entire system more reliable. 2019 WP AER air forks & triple clamp All 2019 KTM models are fitted with the lightweight WP AER 48mm front fork. The damping functions are in the right fork and the air spring is in the left. The left leg features a two-chamber air system with a capsuled air cartridge to prevent loss of air pressure—even if an the outer fork seal leaks the internal cartridge pressure stays the same. There is only a single air valve to adjust and an air pump is supplied with the bike. The CNC-machined triple clamps feature a stiffer upper triple clamps (5% stiffer). The rubber-damped bar mounts reduce the vibration level and are two-way adjustable. An hour meter comes stock already mounted on the top triple clamp. 2019 450 SXF Engine - narrower, half a kilogramme lighter more compact… With its SOHC (single overhead camshaft) Engine weight has been reduced to 27 kilogrammes (with electric starter included). The compression ratio is 12.75:1. The cylinder head is 15mm lower and 500 grams lighter than last year. The gas flow through the newly shaped ports is controlled by a newly configured camshaft with improved cam surface and a shorter valve timing. The four-valve engine uses ultra-lightweight titanium valves (intake 40mm, exhaust 33mm), extremely rigid rocker arms and a low-friction cam chain guide. 2019 350SXF Engine The 2019 KTM 350SXF engine features the new clutch, improved transmission and a re-designed DOHC cylinder head. The reworked cylinder head design is 200 grams lighter than last year. The two overhead camshafts with a friction-optimized superfine surface, finger followers with a DLC coating are taken over as well as four lightweight titanium valves (intake 36.3mm, exhaust 29.1mm). The flow rate has been maximized for an optimal power which ends at an engine speed of 13,400 rpm. 2019 250SXF Engine The 250 SXF engine is known to be the strongest engine in its engine class. And with updates on valve timing, exhaust, airbox and EMS the entire power pack produces even more torque and power across the entire rpm range up to 14,000 rpm. The centerpiece of the compact DOHC (double overhead camshaft) engine is the cutting-edge cylinder head. It features two overhead camshafts which activate the titanium valves (intake 32.5mm, exhaust 26.5mm) via superlight finger followers. The exhaust camshaft features a new timing for improved power delivery. With a low engine weight of only 26 kilogrammes (including electric starter) the KTM 250SXF is the lightest bike in the 250 class. (5KG’s lighter than the closest competitor…) Ride impressions. Two strokes: Unlike some of the Japanese manufacturers, KTM has continued to develop their two-strokes and the net result is a range of bikes that are smoother, faster and more refined. It’s quite easy to understand why their bikes are so successful. Each bike that I rode performed perfectly. The 125SX This is a proper screamer that you need to open wide – especially on a track like this. Gearing, clutch so smooth with so little vibration, easy to ride – a perfect stepping stone for future champs. Very light easy to move around – and I noticed that the two female riders spent most of their time on this one. My advice to young riders – don’t jump from an 85 to a 250 - work your way up the ranks, it pays dividends in the long run. The 150SX My favourite two stroke on the day. It’s also small, light, compact with just that little bit more power that you don’t have to scream all the time it does not work as hard, which probably means that maintenance will be less frequent than on its little brother. The sound of that 150 in the hills is quite something…. I love the smell of two stroke in the morning! They are so light – a bit like riding a BMX with a bad ass engine – ok DIRT & TRAIL MAGAZINE JULY 2018 21

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