The one thing we wouldn’t want to change on the YZ125 is
the Kayaba SSS forks. These forks are still the best forks on
the market hands down.
By adding a tooth to the rear, you can make the usable
power easier to reach, but that means your left foot will be
Q: WHAT CHANGES DID YAMAHA MAKE TO
THE 2017 YZ125?
A: A new 270mm front disc brake (up from 250mm),
which also features a new brake-pad material for improved
pucker power. This is a nice addition and brings YZ125
braking into the real world. As a bonus, the 2017 YZ125
weighs 194 pounds.
Q: IS THE 2017 YZ125 BETTER THAN THE 2017
A: If it didn’t beat out the KTM 125SX last year with
the orange bike’s atrocious 4CS suspension, it isn’t going to
win out against KTM’s amazingly effective AER air forks in
2017. The WP 4CS suspension components were horrible.
MXA testers couldn’t use the power to its full potential,
as the forks were either too soft and bottomed metal to
metal, or were too harsh in the mid-stroke. That was the
past, though. There are no suspension issues for the 2017
KTM 125SX. The KTM 125SX’s combination of great forks,
a bulletproof hydraulic clutch, well-modulated Brembo
brakes, modern looks and a step-above handling leaves the
long-in-the-tooth YZ125 in the dust. All is not lost, though.
We still love the YZ125’s Kayaba SSS components.
Q: CAN THE YZ125 STILL BE COMPETITIVE
WITH THE KTM 125SX?
A: Yes, indubitably, but not without putting cold hard
cash on the line. And, for some reason, the YZ125 went
up in price $109 from 2016 to 2017. Yet, the blue bike is
still $400 less than the KTM 125SX and $500 less than the
clone-like Husky TC125. That difference is cash you can
use to buy some bolt-on power that will make a big difference. What hop-up parts should you buy? Here are a few
suggestions that will get you the most bang for your buck.
(1) Pipe. For less than $250, you can gain around 2
horsepower with an aftermarket pipe (add in $135 for a
silencer). We have had great luck with both Pro Circuit
and FMF pipes.
( 2) Reed cage. We run a Boyesen Rad valve or Moto
Tassinari VForce4 reed cage to broaden the power. The
$179.95 Rad valve or $158 VForce4 reed cage are complete
replacement reed blocks and valve assemblies.
( 3) Cylinder/head mods. A reputable cylinder porter
can get more out of the YZ125 cylinder and head for under
$500, but it’s easy to tune the YZ’s port timing to a standstill. You could end up with a cylinder that works better
holding a door open than on a race bike.
( 4) Gearing. Adding one tooth to the rear, going from a
48 to a 49, will perk up second gear, get you to third gear
sooner and make the overall ratios between the six gears
( 5) Price calculator. If you are thinking of buying the
2017 YZ125 because it is $400 cheaper than the 2017 KTM
125SX, you might want to add up the mods above to see
that your math is seriously flawed.
Q: WHAT DID WE HATE?
A: The hate list:
(1) Chassis. We don’t mind that the YZ125 chassis has
flaws. It is a light bike that is well suspended. That can
cover up a veritable ocean of little glitches. But, we can’t
ignore the fact that Yamaha’s 10-year-old frame numbers
give up a lot to KTM’s up-to-date steel frame.
( 2) Engine. The clutch has to be abused to keep it in
the meat of the powerband. You can buy power, but it will