Lite, Power, Action
Photos by Jay McNally
For 2019 KTM isn’t holding back and is also reacting to the changes being played out in motocross. More aggressive four-stroke power deliveries in search of peak horsepower combined with the lightest weight is the current trend. KTM has always been feathery on the scale and constantly produced the highest horsepower, so weren’t they the target?
As the landscape in the 250cc class changes, things get confusing. All the while the ultimate goal is to sell a bike that is usable for the general public while still being a viable tool for the highest race teams in production class rule racing. Lately Yamaha has proven a player in power and suspension with a more aggressive character and some impressive numbers lower than peak RPMs. Honda introduced an all-new 250F with a top-end heavy power delivery and a light feeling that easily matches anything in the class. So KTM is really just adjusting to an ever moving target.
If you are familiar with KTM’s 250SX-F you know that the power delivery and torque was very linear, almost boring to some if the 14,000 RPM rev ceiling wasn’t enough. The farther you go back in years, the more this was true. So for ‘19 the big change comes from a new shorter intake track with a revised velocity stack that is claimed to be made stiffer to resist flexing and moving around inside the air boot. Then the exhaust cam was retarded a bit in timing. With ignition and fuel mapping changes the 250 SX_F gets what KTM called a “character change”. A claimed ½ horsepower increase is seen from the 12,000-14,000 range. The exhaust system is a US-spec and is also all-new.
Riding the bike you can tell. The great news is that the long pulling torque is still with the bike and it does not fall off for a more novice rider who rolls the throttle on and shifts before hitting the rev limiter. The bad news is that if you start feeling the steps in horsepower at higher and higher RPMs that decent torque isn’t as appealing as keeping the bike revving in a higher power zone. If we were to describe the power deliver in a drawing the new bike would look like steps going up where the old would be shaped like a slide. Keeping the bike on or near the rev cut or between 12,000-14,000 RPMs is a very noticeable difference compared to the 10,000-12,000 area. In the past this was not as pronounced and for each few thousand gain in RPM this is the case. But unlike some 250Fs, especially improperly modified ones, when you fall off in RPM or really and suddenly load the engine the KTM has a little extra torque (likely rotating mass and flywheel effect) to keep thing pushing and give you time for a snap of the clutch or a downshift.
We tested the different maps and launch control for starting. Almost without question we have always run KTM’s in the more aggressive map as they just needed the extra spunk in throttle response. But as KTM boosts the character of the motor we were really happy in map 1 a lot of the time. Map 2 (typically labeled as more aggressive) made the lower end feel a little less aggressive, boosted the mid then had the very top end feeling identical as map 1. Map 1 kinda reminds you to keep the bike in the upper RPM where it is noticeably producing its best power. Map 2 can make you a little lazy with revving. Then the mid range boost can upset the bike in turns if you are not paying attention to your throttle control. Adding in the traction control to each map seemed to put a damper on the motor when the rear wheel spun up–but when getting traction again quickly (soft spots in poof-berms on the track, for instance) the engine would not pull as well if you had just spun across it. If traction was bad all around the track, like in slippery mud, this would work, but not on this track on this day. As for starting mode, the rev-cut feature allows wide-open clutch drops but it is very specific to traction on whether or not it would be an advantage, especially on the 250F.
Also new inside the engine is a beefed-up Pangle transmission to combat quality control issues from other vendors in the past. The five-speed close ratio box keeps the same ratios and in our short time on a few different bikes we did not feel much if any difference in shifting feel. The clutch moves over to a diaphragm spring design like most of the other KTM engines and is activated by a hydraulic system for which KTM have been utilizing for 20-years now. It was excellent.
The chassis changes mirror those found on the 2018.5 Factory Edition SX models and center around gaining more torsional stiffness without transmitting shock loads up through the headset. And anyone with a KTM history know this was a plague for the brand not only in the PDS days but all the way through the WP 4CS era. Looking at the new and old frames side by side there is a different cut-out attaching the head tube and a larger connection for the flow between the radiators. Then there is the engine head stays that now attach near the very bottom of the cylinder head casting and are made of aluminum. A stiffer upper triple clamp also factors into the chassis feel. These changes are small on paper and small if you are not riding bikes back-to-back so feeling these differences might be difficult, if not impossible. They do make a difference and make test riders go nuts when trying to settle on the best combinations for a rounded package. Yet KTM test riders also found that they were getting as much change in chassis feel from these types of parts swapping as they were from different maps and pipe combinations made to the motor. Bikes these days are truly a united package.
We found the bike to be very balanced, extremely light feeling and nimble. With a proper weight and then a heavy weight rider we experienced two different sensations to the chassis that mostly centered around needing the proper rear spring for the heavier rider. The new bodywork lets the rider move all over the bike–flatter front to back and more rounded on the sides feel. Some commented that since it did not stick out anyplace it was hard to “index” where you were sitting based on what you feel in your knees or through your butt. But with great footpegs and adjustable handlebar position it would not take long to find the proper setup and get use to it. And when you are out of the proper spring range (and matching air pressure in the fork) the bike was very prone to dive in the front or squat in the rear depending on where the rider sat on the motorcycle in the turns. It was as if the bike had lost an inch of wheelbase. And this was compounded by the new added “character” in the motor. While still getting familiar with the delivery and where the throttle would best correct any issues our rider who notices these kinds of things said it would just take more time to learn the sweet spots in the power character which usually meant more RPM. For our lighter rider there was no such issue.
We did not feel the need with either rider to mess with the clickers or air pressure in the fork. We just made sure the ride height was good and did laps. The biggest plus of the WP air fork is its lightweight feel and we enjoyed this all day long. This air-spring fork is simple to tune and has much more progression than a spring fork making for a good initial softness with excellent bottoming resistance and we hope KTM keeps progressing with this design while others are adding weight to combat having to check an extra air pressure before each ride. And we tested this a few times with big overjumps and are pleased to report the fork is as good as anything out there. The shock matches the fork from what we could feel, but the track did not get rough enough to give a real evaluation of the suspension’s total performance. But the funny thing to watch and listen to was other media outlets’ riders complain about front end traction and feel (some complaining or attributing it to the tire). When we rode the same bike we very quickly came back in and checked the tire pressure where it ranged from 3-11 PSI too high on different bikes. To an experienced test rider this is blatantly noticeable. So we suspect for those guys spring forks (or maybe a factory mechanic to follow them around so they have a correct setup every time they hop on a bike they intend to test) is a good thing. We’ll take a 3-pound lighter MX bike, thanks.
At a claimed 218 pounds (without fuel and we tend to trust KTM’s numbers these days) this bike is everything KTM claims. Very light on the scale and while riding it, more powerful where advanced riders need it while still being manageable for the regular rider and the suspension is in the game. So yes, this bike still has a target on it’s back.
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