A common mistake. The four stroke does have a wider powerband, but at higher rpm's.
This comes from Motocross Action Magazine:
There is an old saw that states that horsepower doesn’t matter as much as torque. It is assumed that since four-strokes typically produce a boatload of torque, they have an advantage over two-strokes. Guess again, Sherlock! A KTM 250SXF four-stroke is no slouch at 19.42 foot-pounds of torque at 8600 rpm. That is a healthy number, but it pales in comparison to the 250SX’s 31.93 foot-pounds of torque at 8000 rpm (very close to peak horsepower at 8300).
Although the displacements of the KTM 250SX and SXF are the same, the powerbands are horses of different colors.
KTM 250SX two-stroke: The KTM 250SX has a very distinct powerband (as evidenced by its dyno numbers). It hits hard in the middle and pulls across a relatively wide range for a two-stroke. It tops 30 horsepower at 6000 rpm and stays above that until dropping below 30 ponies at 9800 rpm. By four-stroke standards, the power is peaky, snappy and explosive, but the two-stroke’s power is harnessed in a way that magnifies an all-out attack in the usable part of the powerband. It doesn’t rev past 10,000 rpm, but it doesn’t have to, because it gets the job done at an engine-saving 8300 rpm. From idle to 9400 rpm, the KTM two-stroke makes more power than the KTM 250 four-stroke. In fact, there are points along the 250SX’s dyno curve where it makes as much as 19 horsepower more than the four-stroke ever dreamed of producing. The 2012 KTM 250SX is the greatest two-stroke engine ever manufactured.
KTM 250SXF four-stroke: Every test rider who got off the KTM 250SX two-stroke and on the KTM 250SXF four-stroke laughed out loud when comparing the power. “The two-stroke blows the four-stroke away” was the common refrain. In test starts, the two-stroke riders would let the four-stroke go before blasting past it in 100 feet. In back-to-back races against the KTM 250SX, the KTM 250SXF engine felt slow. It revved slower. It had less hit. It droned when the two-stroke went braaappp. But, and this is a big but, while the four-stroke’s hit was less pronounced, there was no wheelspin and no wiggle under acceleration. The slow feel of the KTM 250SXF was misleading. The lack of the sensation of speed wasn’t indicative of a lack of speed on the track. The 250SXF may have been down 10, 15 or 20 horsepower at various stages of the powerband, but after 10,000 rpm, the two-stroke was down 30 horsepower to the four-stroke. What the 250SXF lacked in ponies, it made up in rpm. The four-stroke revved 3000 rpm further than the two-stroke, and during those 3000 rpm, it was making broad, usable and tractable power. The 13,500 rpm rev limiter is 3500 rpm higher and wider than the two-stroke’s working spread.
