2024 KTM 300SX TWO-STROKE: FULL TEST

Once in a while you get a brand-new bike that understands you. Within a few laps of your first ride, you feel like you’ve been on that bike for years; you know exactly what it will do and when.

The KTM 300SX is not one of those bikes. This bike was a game-changer when it was introduced one year ago. It was a completely new model, a completely new concept and a completely new way of looking at two-stroke motocross bikes. Only now, after the 2024 model has been released, are we beginning to understand the bike and what it means for motocross.

STARTING OVER

Prior to last year KTM had never produced a 300SX for the U.S. before; it was up to the buyer from a kit or start with a modified offroad bike. There were a bunch of riders who attempted to race the 300XC in motocross, but it wasn’t a good fit, particularly with the transfer port fuel injection (TPI) that came along in 2018.

That made for a smooth off-road power delivery, but it wasn’t barky enough for MX. The two-stroke engine platform that KTM introduced in 2023 was completely new. It had electric start, an electronic power valve and throttlebody fuel injection. All that stuff had been seen before individually, but with the 300SX, KTM integrated it all in a way that we hadn’t seen before. The bike’s CPU controlled everything, including how far and when the power valve opened. That had never been done before on a production bike. The chassis was also given the same general specs as the four-strokes, meaning it was a little more stiff and had more anti-squat tendencies than the older frames. The suspension still featured a WP Xact air fork in front and an Xact shock in the rear. The brakes and hydraulics were still Brembo, and premix was accomplished the old-fashion way—you mixed the oil and gas yourself.

That bike arrived and blew our socks off. It was fast, hard-hitting and expected us to change the way we rode motocross. We spent a year trying to do just that. So now the 2024 model is here, unchanged, and it has a second chance to make a first impression. This time we’re ready for it. We know that the 300SX is something completely different, and we’ve been practicing our two-stroke mojo.

PRESS THE GREEN BUTTON AND HOLD ON

The first thing you should know about this bike is that it has two maps available on the handlebar switch. They have two very different personalities. The wild ride is the green map on the bottom, and it’s insanely fast. We always hear riders talk about how powerful modern 450 four-strokes are, and technically, the fastest 450 might make more peak power on a dyno than this bike, but that’s just a number. On the track, the 300SX feels more powerful than any of them. It has more to do with the way the power is delivered. Down low, the 300 is smooth and runs super clean. If you have good throttle control, you can actually ride it in the zone below where the real power starts and turn in respectable lap times. But, the KTM’s power ascends with a steep, rapid rush. Modern four-stroke riders might not be ready for this. Most have grown up in the era where smooth power deliveries have accomplished miracles in disguising and making power easy to use. The 300SX has an element of that; it certainly is easier to ride than a ported and polished 250 two-stroke from the old days. But, it’s still harder to control than a 450. On the other hand, it opens up options for different riding techniques. Almost all 450 riders have learned to do all their hard braking with the clutch in. The risk of stalling makes that essential, and then the power is fed in with a delicate balance of throttle and clutch control. With the 300SX, you can brake hard without touching the clutch, and then roll on the throttle old-school. The 300 teaches you real technique, and that makes you a better, more precise rider.

The green map is the one that most riders choose simply because it’s fun. For pros, that’s perfectly fine. Almost everyone else should go with the gray map. You don’t get the big hit, and the thrill factor isn’t quite the same, but it will wear you out less and result in better overall performance. It’s just hard to accept that. In the course of any given race, riders often switch back and forth, which is easy to do on the fly. They usually start off with full power. When they get a little tired and change to the mild map, they inevitably feel like they’re leaving something on the table. It’s human nature. In truth, KTM really needs to offer more than just two maps. Five would be about right. JD Jetting already has a piggyback fuel controller that allows you to alter the mapping somewhat. You can change fuel delivery, but not the spark-advance or power-valve setting. That gives you a little more adjustability, but there’s no adjustment on the fly.

Even though KTM says there are no changes to the bike for 2024, we wouldn’t be surprised if mapping updates are offered at the dealer level throughout the year. There have been reports of occasional glitches. Sound familiar? The same thing happened with the transfer port injection two-strokes, and it was well over a year before the issues were resolved. In this case, the 300SX will occasionally bog when the throttle is closed and opened again at high rpm. Fast downhills like the big one at Glen Helen are usually the location, but it doesn’t happen every time. Is it a big deal? No, it’s hard to imagine a scenario on a fast downhill where a hesitation—actually, more of a hiccup—could get you in trouble.

 

THE KTM FEEL

As far as the handling is concerned, much has already been said about the new frame on KTM’s four-strokes. This isn’t that different. In general, we feel that KTMs are excellent in turns. They’re effortless to steer but not busy. The 300SX is very light; it weighs 223 pounds without gas, which is 6 pounds less than the 450SX. It’s easy to initiate a turn, and it provides a level platform all the way through the corner. But, keep in mind that any two-stroke will behave differently than a four-stroke as you accelerate out of the turn simply because the power delivery is so much more aggressive. The shock is excellent, but the 300SX doesn’t have a bunch of spinning parts like a four-stroke to create a gyro effect. That means that square edges and off-center impacts can throw the bike off course more easily.

The same goes for the fork. We have come to respect and enjoy the WP air fork, too. It’s light, plush and infinitely adjustable. No matter what you do, however, you will find that a 300 two-stroke seems to hit all the bumps harder than a 450 four-stroke. That’s the one advantage that fourstrokes still have, and it’s hard to fix with just suspension tuning alone.

THE NEXT LEVEL

If it sounds like we’re bad-mouthing the sacred institution of two-stroke motocross, that’s not the case. No one loves two-strokes more than us. The fact that the 300SX still isn’t as stable as a KTM 450SX-F won’t surprise anyone who has ridden both, and it’s certainly not an issue that’s unique to the 300SX. And, regardless of the challenges, it’s impossible to ride the KTM 300SX without getting excited about two-stroke MX all over again. It’s a fun bike to ride and a rewarding bike to race. And, on top of everything else, nothing on the track sounds as good.