2017 KTM 125 and 150 SX: First Ride Impression

Big News For Little Pistons!

Photos by Scott Hoffman and Jimmy Lewis

Dirt Bike Test got the jump on the smallest bore KTM two-stroke motocross bikes and is out testing the bikes as you read this. We spent our first day at Cahuilla Creek MX track with a variety of riders (in skill and weight) to get our first impression.

Riding the 2017 KTM 125SX and 150SX back to back made it nice to see the similarities and differences between each bike. Plus, we had just recently returned our 2016 150SX so we were very familiar previous model year for comparison.

The big changes for 2017 include the move to the WP 48AER front air spring fork and the switch to a Mikuni carburetor. Since the 2016 was all-new (see test here) it did not need much, but KTM keeps making quite significant upgrades sooner rather than later. And in the case of the fork, we believe there will be few riders that will complain, although some suspension tuners won’t be so happy.

Right away riders’ are the KTMs no matter what the bike brand they come from or the displacement they typically ride. Everyone thinks these fun-sized racers are super fun. We were supplied a jetting chart and some additional jets with the bikes, which was a good thing, since the track was at nearly 4000 ft. elevation and the temps were high. Switching to a leaner needle on each with a leaner clip position helped tremendously and the chart was spot-on from our perspective running 91-octane pump fuel mixed at 40:1 with Maxima Super M.

The bikes are very similar in power and as expected the displacement tells the story–the 150 is faster. But don’t be so quick to write off the 125 just yet. Every rider said that if they were riding for fun and not trophies they would buy the 125. Why? Because it felt like it has a longer power delivery and utilized the gears better, able to sit on the top-top end screaming without needing a shift. That said everyone but our most novice rider felt the 150 was notably faster and it was obvious to riders above the typical weight range for these bikes. It pulls easier from a lower RPM without as much clutch.

Once you are south of the 180 pound size, the torque and pull of the 150 is very noticeable and basically requires one less downshift in every turn on the bigger SX. The Mikuni carb gives the SX a little more hit and a little more power than the 2016 but also uses a little more fuel then the Keihin of 2016. Both bikes have a very long winded pull and shifting and gear ratios (different final drives) were spot-on for this track.

We found that incremental tuning to the powervalve could yield different overrev and pick-up feelings to each bike and riders had different preferences once they noticed the ease at which this could be changed.

Onto the suspension and chassis where KTM is pushing a good thing even farther. The chassis was already excellent with a very easy to move around on layout and for most a very balanced ride. Going to the air fork drops nearly four pounds from an already light bike and the action of the fork is worlds better than the older 4CS design. Now the 125/150SX dances around a whole lot less and still has the progression and the bottoming resistance it needs. The rear is a lot more active feeling now and this helps the bike settle into turns and have better initial bump compliance. Even more impressive to our more sensitive riders was the even lighter feeling through the turning of the handlebar and a much nicer slap-down feeling when landing from jumps.

All it took was the proper spring preload setting on each of the bikes for the rider’s weight and maybe a click or two of compression or rebound and there wasn’t a complaint. We were also able to see how the settings could really change the bike’s feeling with back-to-back riding on the two different displacements with different settings. With just a few clicks in change between the bikes really changed the feeling in the bumps or on jump landings.

There is no doubt these KTMs are better than the previous year’s models just in the lighter weight feel and the overall suspension performance. It is enough of a change in feel that most brands would call this an all-new bike. We’ll keep riding and racing them and get the full test to you soon.

If you have any questions you’d like answered, use the comments below and we’ll try and get those sorted in testing.