Stiff upper lip: Unlike the KTM 350SXF and 450SXF, the KTM
125SX has the perfect shock spring rate.
brakes seem to be mellower, but that’s okay because they
are still best-in-class.
( 4) Tires. KTM must have read our test on the Geomax
MX32s in comparison to last year’s Geomax MX52s. The
KTM line is the only brand to come stock with premium
intermediate-terrain race tires.
Q: WHAT ARE THE DIFFERENCES BETWEEN
A 125SX AND A 150SX?
A: To the naked eye, the KTM 125SX and 150SX
look identical. They share the same suspension, frame,
shock linkages, brakes, wheels and engine architecture,
but they aren’t identical twins. Here are the six
(1) Displacement. The 125SX has a 124.8cc
displacement, while the 150SX is 143.99cc.
( 2) Bore and stroke. The 125SX’s bore and stroke is
a classic 54mm by 54.5mm, while the 150SX has a larger 58mm bore combined with the same 54.5mm stroke.
With both bikes having the same stroke, the cylinders are
interchangeable. The 125SX can be made into a 150SX
and vice versa.
( 3) Gearing. More power can pull taller gearing, thus
the 150SX comes with 13/48 gearing while the 125SX
( 4) Parts. The cylinder, piston, power valve, head
stays, power valve governor spring and rings are different
on the 125SX and 150SX.
( 5) ECU. The ECU is the standard KTM unit, but the
150SX and 125SX each have unique mapping.
( 6) Jetting. The 125SX has a smaller main and pilot
jet, as well as a different needle.
Q: HOW FAST IS THE 2016 KTM 125SX?
A: It is no secret that 125cc two-strokes are at the
bottom of the totem poll in terms of sheer power. For
2016, the KTM 125SX has closed the gap on the 250
four-stroke bottom dwellers, such as the CRF250. On the
track, the 125SX has a perky powerband that is easier
to ride than in previous years. This low-end grunt is a
sensation that its main competitor, the YZ125, lacks.
The YZ125’s short powerband is more of a light switch
when compared to the high-rpm 125SX. With the YZ125,
you either have the throttle off or you are feathering the
clutch until it flickers on. Don’t get us wrong; last year
we favored the YZ125 over the KTM 125SX, but there is
only so much horsepower a decade-old bike can give up
before it isn’t in the running anymore. The KTM 125SX is
very fast for a 125cc machine.
Q: HOW DOES THE 2016 KTM 125SX RUN
ON THE DYNO?
A: The 2016 KTM 125SX makes a whopping 37. 27
horsepower and 17. 35 foot-pounds of torque on the dyno.
That is an iota below the 2015 Honda CR250F four-stroke.
At peak, the 2016 KTM 125SX makes a little over 2
horsepower more than the 2015 KTM 125SX and the 2016
overpowers the 2015 by one horsepower or more from
9000 rpm to 11,000 rpm. But, whereas the 2015
KTM 125SX peaked at 11,200 rpm then sharply fell off
the pipe (to a measly 27. 67 horsepower at 12,000 rpm),
the 2016 KTM 125SX pumps out 7 more ponies at 12,000
rpm and over 2 horsepower at peak, which is 500 rpm
higher. Compared to the YZ125, the 2016 KTM 125SX
produces 3 horsepower more at peak. The 2016 KTM
125SX is the best-running 125cc we have put on the
dyno to date.
Record setter: The 2016 KTM 125SX makes a whopping 37. 27
horsepower. That’s encroaching on 250 four-stroke territory.