This 12 months KTM tossed all the things about its current two-stroke motocross bike within the trash. The motor within the earlier SX two-stroke had served KTM nicely. It had acquired a significant replace in 2017, however hadn’t provided expertise or ideas that have been really new. It nonetheless had a Mikuni carburetor, a kickstarter and a ball-ramp mechanism working a mechanical energy valve. All these issues had been round because the ’70s. Now, KTM has began over.
WHAT’S SO DIFFERENT?
One of the vital superficial modifications is the brand new displacement. There was no 300cc motocross two-stroke in KTM’s American line-up final 12 months. There have been 300cc off-road bikes and a 300cc equipment for the 250SX motocross bike, however the motor wasn’t really designed to be that displacement. Riders who put in the 300 equipment on the 250 bumped into issues with the ignition and an absence of rpm. In the event that they received round these points, they’d reliability points. KTM was additionally reluctant to deliver gasoline injection to a two-stroke motocross bike. Their engineers had invested an excessive amount of time and growth into Switch Port Injection (TPI), however that at all times appears extra acceptable for an off-road bike. KTM didn’t use electrical begin or an digital energy valve, both. They mentioned they favored the simplicity of the prevailing bike, which integrated a ball-ramp energy valve and a kickstarter.
The 2023 motor was designed round throttle-body gasoline injection, which is principally what a four-stroke makes use of. Switch Port Injection and oil injection stay solely on the off-road bikes. The electronics bundle was additional sophisticated by bringing electrical begin and an digital energy valve. Digital energy valves have been used earlier than, however we haven’t seen something like this. Earlier designs have acted like mechanical energy valves. They have been open or shut. All that engineers might work with was how shortly they opened and at what rpm. KTM’s new system is pushed by the identical CPU that operates the gasoline mapping and spark advance. It appears to be like at rpm and throttle place to find out when and the way far the ability valve ought to open. Which means the ultimate mapping is much extra advanced than something seen beforehand on both the two-stroke or four-stroke.
All of KTM’s 2023 full-size motocross bikes received a brand new chassis, together with this one. The body is extra inflexible and has a brand new shock and rear suspension format. The entrance suspension continues to be a WP Xact air fork, and the hydraulics are nonetheless by Brembo, together with brakes and clutch. When it was all accomplished, the brand new bike did achieve some weight. The earlier 250SX was 215 kilos. Now, with the battery, the starter and the brand new body, the KTM 300SX is 223 kilos.
RETURN OF THE OPEN-CLASS TWO-STROKE
We like to toast the sheer energy of old-timey 500 two-strokes, however in actuality many trendy 450 four-strokes have attained horsepower numbers in the identical neighborhood—someplace within the mid 50s. The five hundred two-stroke received there with torque and trendy 450 four-strokes do it with rpm. The 300SX does it with each. At low rpm, the 300SX has unimaginable pulling energy. It’s virtually startling, however that’s nothing in comparison with what’s ready later. Within the mid-range, the 300 goes just a little loopy. It hits with power and venom, so that you higher be ready. The motor pulls so arduous and goes via the center rpm degree so quick that almost all riders hen out and upshift early. In case you attempt to roll off just a bit, you find yourself in a really awkward place the place it’s really tough to dial in the correct amount of horsepower. If, alternatively, you keep in all of it the best way to peak revs, you find yourself accelerating as arduous as any bike made. The 300 nonetheless doesn’t produce the height energy or rpm of a 450 four-stroke, but it surely’s shut sufficient. You simply must have someplace to go, and most motocross tracks aren’t manufactured from straight traces.
If that sounds just a little intimidating, that’s okay. We like bikes that scare us just a little. The trick with the 300SX is studying to make use of that loopy zone within the center. For a lot of components of the monitor, you’ll be able to upshift and let the torque do all of the give you the results you want. In case you enter a nook at low-to-middle rpm, you’ll be able to pull a lot of the means via with out touching the clutch. Then, when you’re strapped in and able to go, you hit the clutch as soon as or simply anticipate the fireworks to start. Convey your A-game. It’s an absolute blast once you do it proper. However, as everyone knows, a couple of laps right into a 20-minute moto your A-game begins slipping away. The engineers and check riders at KTM know that, which is why the 300SX has the sissy change. Different riders may name it a map change. There are two buttons—one prompts a inexperienced map and the opposite is a white map. Trip with the inexperienced map once you’re feeling sturdy and wanna have enjoyable, then go to the white map once you’ve had sufficient. The white map tones down the hit significantly. It additionally shaves just a little energy off the highest. It’s the good map to make use of more often than not, however be forewarned: when you’ve tasted the wild facet, it’s arduous to return.
THE GREAT HOPE
KTM went all in with a brand new body for 2023. Between the KTM and Husqvarna traces, the body comes on over 20 new fashions. That body doesn’t make associates simply. Initially it comes throughout as stiff and unforgiving. After some time, it grows on you. One concern is that it “breaks in” and will get extra compliant with time. One other is that its biggest property are extra obvious in extraordinarily tough circumstances that don’t present up that always, whereas its stiffness is obvious on the trip to the beginning line.
The body for the 300SX isn’t precisely just like the one used on the four-strokes, but it surely’s very, very shut. It has the identical steering geometry because the outdated one, which implies it’s wonderful in turns. It drops in simply and lets you make changes mid-turn. However, it provides you an identical preliminary suggestions because the four-stroke body—it’s very stiff on small impacts and easily not as comfy because the older, flexier body. Moreover, there’s the two-stroke think about uneven terrain. You don’t get the invisible hand of gyroscopic stability that four-strokes supply. On acceleration, sharp edges make the bike deflect extra. The hard-hitting energy supply combines with that to make traction tough to search out and maintain.
What meaning to a racer is that there are occasions when he’s going to must work just a little tougher than his buddies on 450 four-strokes. The rougher the monitor, the extra the two-stroke will battle to place all that energy to the bottom. On the flip facet, a monitor with good traction and fewer square-edge bumps is 300SX heaven. Once you’re all lined up with easy chocolate dust earlier than you, there’s nothing as satisfying as feeling that green-map energy surge take you to the following flip in warp drive.
So, despite the fact that the brand new 300SX modifications the two-stroke recreation in motocross, it stays a really specialised bike. It gives sensations and emotions that no four-stroke can duplicate. Heading in the right direction, it may possibly tackle a contemporary 450 face to face. As soon as you start thinking about the true world with a cross-section of flawed, ill-prepared tracks, nevertheless, it’s clear that the 300SX is a motorbike that can find yourself being extra enjoyable to trip than it’s to race.
