Yamaha and KTM have kept premix purists very happy over the years with continual support of two-stroke machines. The 2017 KTM 250 SX is an all-new motorcycle, with the orange engineers focusing on weight reduction, centralizing mass, improving handling, and of course trying, and getting, more power out of the engine. The company also made updates in the ergonomic department to give the SX an all-new, fresh SX-F look. Meanwhile the 2017 Yamaha YZ250 hasn’t changed in quite some time (other than cosmetically), but its solid footprint in the two-stroke realm keeps it relevant, competitive, and a threat in the midsize premixed department. We took both of these machines to several tracks to really compare each of their characteristics and see which stacks up better.

Engine

You couldn't find two more completely opposite engine characteristics between these two bikes. The KTM 250 SX builds rpm a little more calculatedly and is almost four-stoke-ish when coming out of corners. The Yamaha YZ250 is more barky (at low rpm) and has an exciting throttle response and bottom-end.

Yamaha YZ250
The YZ250 has been the standard bearer for years.Jeff Allen

Exiting loamy corners is when you can really feel the Yamaha’s increased throttle response. When the track gets chewed up and rough the KTM’s power delivery is easier to manage; it has a ton of rear-wheel traction for a two-stroke. Midrange on both bikes is very good, but the KTM likes to be shifted early and doesn’t quite rev as far in each gear as the Yamaha. Coming out of second gear in corners and accelerating, the KTM falls off quickly whereas the Yamaha will pull further down the straight.

After experiencing this on a couple of tracks we decided to ride the KTM in a higher gear, and to our surprise the 250 SX prefers this method of riding. The Japanese Yamaha engine likes to be ridden aggressively, and although the KTM can do that to a certain point, this Austrian motor is more of a lazy man’s type of engine character. Top-end on both bikes in third and fourth gear is similar, but it’s the way you get up to third gear that makes them so different.

KTM 250 SX
The KTM is a lazy-man's 250 two-stroke.Jeff Allen

The KTM also provides much less engine-braking than the Yamaha. You might be asking yourself, “Are they really talking about engine-braking on two-strokes?” Yes, we are! In fact, it is so noticeable that it was one of the first comments to come out of all of our testers’ mouths when they rode them back to back for the first time.

Suspension

Both machines have a great suspension feeling, but the Yamaha pleased us a little more at a wide variety of tracks. The KYB SSS fork has tons of damping feeling and feels firm yet doesn’t deflect or feel harsh anywhere throughout its stroke. The KYB fork is also more consistent and feels the same over the course of the day even when track conditions change.

KTM
The KTM has air forks while the YZ still has springs up front.Jeff Allen

This doesn’t mean the 48mm WP AER fork is bad; it just didn’t react the same when we took it to a variety of tracks. For example, we tested at a soft-sand track and the AER fork moved too much through the stroke and was dive-y, so we tried adding (stiffening) compression. This helped some but gave us an increased harsh mid-stroke feel. We then went with a little more air (from 10.2 bar to 10.3) and backed out compression and found this a better setting, but we still didn’t quite have the comfort on small bumps like the YZ did. On hard-packed, square-edge tracks the AER fork felt good, moved through the stroke well, and gave us better front-end traction than the YZ. However, the YZ still was predictable and wasn’t that far off in comfort from the KTM on hard-packed, rough-track days.

Both shocks on both bikes were great on all tracks we tested on. The different feelings between the two were: The KYB shock on the YZ gives the rider more movement in the rear end and tracks the ground nicely. The WP shock has more of a dead feeling and moves less over bumps, though the rear wheel tracks the ground equally as well.

Chassis

It’s hard to beat the lightweight feeling through corners of the KTM. Direction changes are easier on the KTM (even with the mellower bottom-end snap), as the rider can cut down from a berm and get into a rut with less effort. Bump absorption on the KTM is also slightly better on square edges. You can only feel the difference when the track gets super baked and hard-packed. On softer tracks both frames on each bike do a great job of providing comfort and stability.

YZ250
The YZ's suspension is incredibly predictable.Jeff Allen

On hard-packed tracks the Yamaha will deflect a little more off of small, sharp bumps when leaning. The KTM remains planted, and the sensation the rider gets is that of more tire contact to the ground. Depending on what type of rider you are will determine which bike you will say corners better. Most rear-end steering riders like the Yamaha more coming into corners, and front-end steering riders prefer the KTM.

Vibration is also another key element when debating two-strokes. The KTM has zero vibration through the handlebar and pegs. The YZ doesn’t have a lot, but when you have next to no vibration for comparison, any vibration is magnified and the Yamaha gives the rider more buzz through the gloves and boots. Ergonomically both machines fit our smallest tester 5-foot-8 to our tallest 6-foot-1 very well. None of them complained about being too spacious or were cramped on either machine.

KTM
The KTM's lack of weight feel is unparalleled.Jeff Allen

Who Wins

So who wins this two-bike two-stroke shootout? We would have to give the nod to the 2017 KTM 250 SX. The suspension isn’t better than the Yamaha, but it’s close. However, the KTM is easier to ride, feels lighter, has less vibration, and takes less effort to go fast around the track. If you are looking for that barky, snappy throttle response, then the Yamaha would be your pick. Both of these machines are capable of giving any type of rider (four-stroke or not) endless amounts of fun on the track. It could also bring back the fun, possibly some extra money (in savings) in your wallet, and some welcome simplicity if you are somewhere lost in the four-stroke technology Twilight Zone.

Yamaha
Yamaha YZ250Jeff Allen
2017 KTM 250 SX
MSRP: $7,699.99
Seat Height: 37.8 in.
Ground Clearance: 14.7 in.
Fuel Capacity: 1.9 Gal.

What's Hot:

  • Zero Vibration
  • Rear-Wheel Traction
  • Easy-To-Ride Engine Character

What's Not:

  • Lack of Bottom-End Excitement
  • Fork somewhat hard to dial in on different tracks
  • Shroud can interfere with some knee braces
KTM
KTM 250 SXJeff Allen
2017 Yamaha YZ250
MSRP: $7,399
Seat Height: 39.1 in.
Ground Clearance: 14.2 in.
Fuel Capacity: 2.1 Gal.

What's Hot:

  • Bottom-end excitement
  • Suspension comfort
  • Proven durability

What's Not:

  • More vibration
  • Engine hard to ride when track is slick
  • Dated look

Opinions

Michael Allen | 6'1" 180 lb. Novice
After 10-plus years the Yamaha YZ250 is finally showing its age. When compared to the 2017 KTM 250 SX, the YZ has more vibration felt through the bar and footpegs and lacks some modern styling that the KTM has. The Yamaha's engine has a more linear feel with strong power throughout the rpm range and also has more engine-braking than the KTM. For me, the KTM engine is the smoothest 250 two-stroke engine in history, and I feel it's more powerful than the YZ, even though it has a soft feeling down low. It has minimal engine-braking when entering corners. After time on both bikes the Yamaha feels a little outdated, but I think it's the bike for me. The reason I prefer the Yamaha is that I prefer the KYB spring fork feel when the track gets rough, as it stayed consistent throughout the day. I also like the fun factor the bottom-end gives me out of corners.

Matt Bynum | 5'10" 160 lb. Intermediate
After spending a few test days riding the two bikes, I was able to come to a conclusion on which bike I preferred: KTM. Right away I noticed the KTM did not have the typical overwhelming two-stroke vibration, which made it feel much more comfortable on the track. As soon as I fired up the Yamaha I noticed the vibration was far more substantial. Both bikes have a good motor; however, in this department I enjoyed the Yamaha more. I felt the KTM revved out sooner and signed off far too early, with the Yamaha I felt it had much more midrange. It pulled longer and offered more over-rev. On to handling characteristics, I felt both bikes were rather easy to maneu­ver, but the KTM won here. It was much easier to turn the KTM, especially in deep ruts. The Yamaha just simply felt less nimble, while the KTM felt very light and easy to ride. On the suspension side, I liked the Yamaha more just because I felt it wasn't as soft as the KTM and seemed to hold up better when the track got choppy. Overall, I liked both bikes, but the KTM was easier to ride than the Yamaha and much more enjoyable with the track conditions where we tested.