The KTM 125SX powerplant pumps out 37. 27 peak horsepower and 17. 35 foot-pounds of torque. It weighs 197 pounds.
team of test riders made no adjustments other than sag for
their weight. It was in the ballpark right out of the gate.
This shock is not up to the Kayaba YZ125 shock standards
yet, but it is closing the gap each year.
Q: HOW DOES THE KTM 125SX HANDLE?
A: Better than the 250 or 450 four-stroke that is sitting
in your garage. We are not just talking about the 125SX,
but also the YZ125, TC125 and MX125. These bikes are
25 pounds lighter than most 250 four-strokes and don’t
have the rotating inertia of a valve-and-cam engine to deal
with. The reduced gyroscopic effect of a two-stroke engine
allows a racer to put the bike where he wants. Plus, you
can throw it around in the air with ease and manhandle
it in the rough (as opposed to being manhandled by a
thumper). The KTM 125SX is incredibly fun to race just
as long as you are willing to hold the throttle to the stops
and fan the clutch.
The 2018 KTM 125SX is the best-handling bike in its
class. Some MXA testers think they can push the YZ125
harder, but that’s because they are going slower on it.
Q: HOW WAS THE STOCK GEARING?
A: In stock trim, the 2018 KTM 125SX could use a
bit more bottom and mid to get it moving quicker out of
corners and in deep loam. Our faster riders opted to use
their throttle hands to keep the powerband in the sweet
spot. Slower riders went from a 50-tooth to a 51-tooth rear
sprocket to help them get to the power sooner—and, most
important, to make third gear more effective.
Q: WHAT DID WE HATE?
A: The hate list:
(1) Gas cap vent hose. KTM’s vent hose gets twisted
in a knot when you take the cap on and off to fill the tank.
( 2) Preload ring. The plastic preload ring needs to be
beefed up. “Beefed up” is code for “made out of metal.”
( 3) Power valve adjuster. The square power valve
adjuster is ridiculous. Have you ever heard of a Robertson
wrench? Nobody can find a tool like that. Making it into
an Allen or Torx would be a step in the right direction.
We do a lot of KTM power valve tuning and always use
a flat-bladed screwdriver instead of the proper tool. KTM
does have a Robertson wrench in its Power Parts catalog.
( 4) Bleed screw. The fork’s air bleed screw is a #20
Torx. We change it to the Phillips head bleed screw from
the 2016 model on the right fork leg and use a 10mm
T-handle on the left side.
( 5) Wheels. The rear spokes never want to stay tight,
especially the one by the rim lock. We have better luck
with the Husky’s D.I.D DirtStar wheels.
( 6) Carburetor. The new Mikuni carb works better
than it did last year, but not as well as the old Keihin did.
( 7) Grips. We love the feel of the stock ODI lock-on
grips. We always love how easy they are to change; but, if
you don’t own a #10 Torx, they aren’t coming off.