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ASK THE MXPERTS: What Is The Difference Between A KTM 150SX vs. KTM 125SX? How Much Power Does It Make Compared To A 125 Or 250 Four-Stroke?

March 11, 2009
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KTM 150SX vs. KTM 125SX

Dear MXA,

   Have you dyno tested the KTM 150SX? Have you compared it to the KTM 125SX? Have you tested it against 250 four-strokes?

   Yes, yes and yes. Where the KTM 125SX has a smooth, linear and road racey powerband, the 2009 KTM 150SX powerband is much chunkier off the bottom and through the middle.

   Torque is up two foot-pounds from 6000 rpm to 10,000 rpm (and one foot-pound until sign-off). A more telling comparison is between the torque of the 125SX (17.8 ft-lb), 150SX (18.9 ft-lb) and 250SXF four-stroke (19.2 ft-lb). The 150SX closes the torque gap to the four-stroke, which is what a four-stroke uses to get hooked up better than two-strokes. The 150SX’s additional torque is more important on the track than its horsepower figures.

   The horsepower numbers favor the 150SX over the 125SX (and over the 250SXF also). The 2009 KTM 150SX almost tops 40 horsepower at peak (which is about 300 rpm lower and two horsepower more than the 125SX’s peak). Best of all the 150SX makes as much as three horsepower more than the 125SX in the meat of the powerband.

   If we were going to choose a 125 two-stroke to race against 250 four-strokes, we would choose a big bore. The extra horsepower and torque (especially the torque) make the 150 a better bike to go up against four-strokes.

   Do we think it will beat a 250 four-stroke? We’ve seen guys on weak RM125’s win Vet races against riders on 450s. So, anything can happen. The 150 can beat them when used to its fullest. It will definitely beat a 125.

   The March 2009 issue of MXA has a full test on the 2009 KTM 150SX and 250SX.


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