rpm. The 125SX may seem weak, but it is making more horsepower and torque than the 2013 Yamaha YZ125. Q: WHICH ONE IS FASTER? A: Going fast isn’t always about the most horsepower; although, in perfect conditions, horsepower will always win. At straight-line speed, the KTM 150SX two-stroke can run circles around the KTM 125SX. During our test period, we faced several big step-ups out of tight corners that the 150SX could do and the 125SX could not do. There is no replacement for displacement on the face of a jump. But, motocross doesn’t take place in a straight line. Cumulative power is noteworthy, but the layout of a racetrack often favors the best all-around powerband over the one with the most thrust. How can that be? Every MXA test rider preferred the 150SX’s burst of power, harder hit and stronger pull when they first started racing the two orange machines. But, a funny thing happened on the way to the forum; they all decided that the 125SX was actually a better race bike. It carried its speed better, rewarded all-out attacks and had a powerband that, although down on ponies, was up on usability. It was a better blend of power—although not an abundance of it. That doesn’t mean that the 150SX was a dog. Once we switched from lightweight 125 specialist test riders and went to slightly heavier Vet test riders, the quorum at the forum switched in favor of the 150SX’s more potent power. Q: WHICH BIKE PRODUCED THE BEST RACE RESULTS? A: Every MXA test rider had his favorite before he raced the KTM 125SX and 150SX. We spent an inordinate amount of time switching bikes between test riders at the races—doing one moto on the 125 and the second moto on the 150. But, surprisingly, the voting pattern remained the same. The smaller test riders favored the 125SX for its fluid gear-to-gear feel on the track, while the Vet riders favored the more vigorous blast of power that defined the 150SX. The major factor that swung the vote one way or the other was the start. The 2013 KTM 150SX was much easier to get a good start on than the 125SX. This did not play a role in 125cc two-stroke races, but when classes were mixed, with 450cc and 250cc four-strokes in play, the extra power of the 150SX came in handy. Q: WHAT MOD SHOULD EVERY RIDER MAKE? A: Our Pro-level test riders didn’t complain as much about the stock gearing on the 125SX and 150SX as our Novice, Intermediate and Vet test riders (and since these aren’t Pro bikes, we tend to listen to the amateur wish list more). We would swap the stock 125SX sprocket for a two-tooth-larger cog immediately. And, on the 150SX we added one tooth to the rear. There is one caveat, however; if you go two teeth bigger, you must commit to getting into third gear quickly.
2013 KTM 150SX: At 38. 88 horsepower,
the KTM 150SX has plenty of low-end
grunt. The larger tiddler is best suited
to Vet riders looking to have a lot of fun
while still being competitive.