This article was originally published in the June 2017 issue of Dirt Rider.
Life is full of choices, right? Like picking the correct size dirt bike for your style and riding ability. Questions flood in all the time about which size motocross machine is right for our readers. So we decided to put this question to the test. We picked five riders who ranged in weight and ability to ride the 2017 KTM 250 SX-F, 350 SX-F, and 450 SX-F in a controlled environment. We enlisted LitPro and its helmet-mounted GPS-enabled data system to help us track each rider’s lap times and progress (if any was made) throughout the day of testing. None of the test riders were told their lap times during the test, as they had to pick which bike they felt most comfortable and thought they were fastest on. Below are their opinions and ranking (in order), as well as their best lap times on each size.
Here is a quick refresher of what each KTM engine and chassis character is like from when we tested them earlier in the year.
250 SX-F: The 250 SX-F doesn't have a big bottom-end hit but churns out mid- to top-end horsepower like no other 250 in the class. You can't lug it as much as other 250s, but if you are a screamer and like to get the most out of each gear, this might be the right engine character for you. The chassis is light and nimble and is a very capable cornering machine. The fork can get a little soft at times for a heavier rider, but overall balance of the KTM 250 SX-F is comfortable and plush.
350 SX-F: More torque than a 250 SX-F out of corners, but the 350 pulls similarly to the 250 in the mid- to top-end power. The 350 can be lugged a little more than the 250 yet still prefers to be revved out like the 250. The chassis is still very 250-esque feeling and can be flicked around just like its little brother. The fork, however, is not quite as comfortable through the mid-stroke like the 250 and 450 and can be somewhat hard to dial in at certain tracks when there are bigger braking bumps. Vibration is not an issue when the engine is spooled up.
450 SX-F: The Big Bertha of this group feels super light compared to other 450s in its class. The engine character is smooth off the bottom, but you are able to carry second gear longer on this 450 than all other competitors in its class. Mid- to top-end is more than you will need but will never rip your arms out of their sockets while increasing the throttle. The WP suspension has enough movement and hold-up for an aggressive rider but is also stiff enough for a slower rider who may not be able to clear all of the obstacles on the track.
Starting with the 250 SX-F, I personally enjoyed this bike a lot. To me it feels so light and nimble I can go anywhere on the track. Since I am accustomed to a 250 (because that’s what I race) it was easier to feel at home on this size of a machine. Aside from great handling characteristics and comfort, this bike has a strong engine package; however, I don’t find it quite up to par with its bigger brothers. It pulls hard throughout the midrange and really shows its strength on top, but I noticed a rather large lack in bottom-end power. I really like this bike, yet the engine lacks in bottom-end power, making it my second favorite.
This 350 is hands-down one of the most fun bikes I have ridden. I feel this bike shows off its light and nimble characteristics, which were very notable on the 250. The 350 was my favorite for its engine, which allowed me to ride it like a 250F and stretch out each gear. It is a very free-revving bike, and you are also given the option to ride it like a 450 and ride it a gear high easier than you can with the 250. With the 350’s super-responsive bottom-end rpm response and midrange pulling power, as well as its ability to rev far like a 250F, this in-between cc’d bike is a very good option for a rider like me.
Moving on to the biggest bike in the SX-F lineup, the 450 was my least favorite. The reasons were the fork and engine. Starting with the fork, I felt that it did not offer much rider comfort for my weight. One of the biggest characteristics I look for in a bike is a plush ride, and I want a bike that offers as much rider comfort as possible. Being more of a 250F rider, I want very smooth, less scary, linear power on the bigger bike. The 450 was just a little too aggressive for my liking, and I was more timid on this machine out on the track. I felt it had a very hard-hitting power delivery and was a very solid motor, but I think the 450 SX-F is geared more toward bigger riders and/or riders who have had time on big bikes.
—Matt Bynum
5'10", 155 lb., Intermediate
Personal Ranking: 1. 350, 2. 250, 3. 450
Actual Lap Times: 2:02 (350), 2:05.47 (450), 2:05.50 (250)
I consider myself a 250F rider, but I was amazed how much more fun the 450 was to ride than either of the other two bikes. I stuck to the vet track with shorter straights, and the 450 felt more nimble, more precise, more planted, and more fun; it laid into turns perfectly. It got better traction front and rear, and the strong power was fun to modulate.
The 250F probably had the best suspension for me. It was comfortable and predictable, but the 450 had more accuracy. The 350’s ends just didn’t work in unison; the bike rocked front to back through the bumps. The 450 had strong, meaty power from the bottom-end on up, where the 350 had a great bark down low but ran out of “go” before my straightaways did, and I had to shift where I did not on the 450. So the 350 requires the same amount of attention to throttle control down low without the reward of a long pull once you are hooked up. In that bottom-end rpm where I ride, the 250’s power felt a big, big step down from the 350’s.
If I told myself I was going to get into great shape then somehow believed it, I would pick the 450 easily as my favorite; right now I pick the 450 with some reservations since it takes more energy and would be too much bike at many tracks, with the 250F a close second, and the 350 a distant third.
—Pete Peterson
5'10", 175 lb., Vet Novice
Personal Ranking: 1. 450, 2. 250, 3. 350
Actual Lap Times (Vet Track): 1:47.25 (450), 1:47.42* (350), 1:50* (250)
I own a 2015 KTM 350 SX-F, and this was my first time ever riding the KTM 250 and 450. I have always been a little afraid of the power of a 450, and that’s why I purchased the 350 when I stepped up from a 250F. The 450 has a lot more power than the 350, but it is not as light and nimble; yet it did give me the confidence to jump the larger jumps on the track that I didn’t try on the 250 and 350. Still, I felt slower in the turns because of how big and heavy it felt underneath me.
The 250 feels super light and was awesome in the turns, but coming out of them it felt underpowered and I had to shift a lot, plus I did not feel comfortable jumping a few large tabletops out of tight turns because I couldn’t get the bike to soar over them without revving the motor to its limit.
Then I hopped on the 350, and I felt right at home. The 350 just feels so right for me and my skill level. It’s easy to ride, corners amazingly, and has the power when I need it. I trust this bike more than I trust the 250 or the 450. I also felt that my fastest laps were done on the 350. I would say that the 350 outperforms the other two by a long shot for me.
—Steve Caballero
5'3", 160 lb., Vet Novice
Personal Ranking: 1. 350, 2. 450, 3. 250
Actual Lap Times: 2:22 (350), 2:25 (450), 2:27 (250)
I am very familiar with all these bikes. I rode the 450 first, and since I prefer a larger-size bike I immediately became accustomed to it. I am a smooth type of rider who likes to roll the throttle on calculated coming out of corners, and finding creative lines is key for me to go fast around the track. The KTM 450 SX-F lets me do this and agrees to my riding style the best.
The 350 is a little more hyperactive than I want out of a machine but is still so much fun to ride. The track we tested on was faster with bigger-size jumps, and the 350 had no problem clearing them all. However, I feel like I can’t lug the bike as much as I prefer, especially when the track gets hard-packed and choppy. The more I rode the 350 like a 250, the better I felt my lap times were getting. I do like the free feeling of the engine and the lack of engine-braking on the 350 the most, however.
The 250 plain and simple just doesn’t have enough power for me to take inside lines and clear obstacles. In order to get over those obstacles I have to seat-bounce the jumps, and my back has too many miles on it to keep riding like that. The 250 felt awesome to lay into corners, but coming out of them is where I felt it lacked the fun factor for me.
—Kris Keefer
5'11", 170 lb., Pro
Personal Ranking: 1. 450, 2. 350, 3. 250
Actual Lap Times: 1:54 (450), 1:57 (350), 2:02 (250)
The 250 was just easier to manage everywhere on the track. I felt like I could be more aggressive. When the track became rougher and drier, I was able to stay on the throttle longer through the turns. It was a little low on low-end power after coming off of the larger bikes, so you had to rev the bike out. When it comes to jumping I usually like to have a little more power to accelerate on the face. While riding the 250, it took more speed before you made it to the face.
The 350 had everything I like in all three of the bikes! I was able to ride this bike almost as aggressively as the 250, but I had the power to launch over the jumps that I couldn’t clear on the smaller bike. The power delivery was great and as long as the 250’s. I was not able to notice a power difference between the 350 and 450, but the 350 did seem easier for me to hit the ruts. I feel like I can ride the smaller bike faster than the 450.
I would buy the 450 if I was 6 feet and weighed 180 pounds. With me being a little out of shape and not able to muscle the more powerful bike around I feel like I get tired sooner. However, the 450 is smooth and easier to ride; it becomes more of a handful when the arms get pumped up.
—Kelly Gelhaus
5'9", 245 lb., Senior Intermediate
Personal Ranking: 1. 350, 2. 250, 3. 450
Actual Lap Times: 2:21 (250), 2:25 (350), 2:33 (450)
Some of the riders “thought” they were fastest on one bike, but lap times don’t lie. However, most of the lap times were close enough between the testers’ top pick and their actual fastest times. The rule of thumb is if you feel confident on a machine, it usually is the right choice. The fastest bike is not always the correct one to choose. The correct machine is the one you feel you are able to do the most with on the track and not necessarily the bike that gets you from point A to point B the fastest.
