First Impression: 2019 KTM 300 XC-W TPI 3

Measuring and mixing premix is a thing of the past… or is it? Two-stroke loving motocross riders might not want to hold their breath.

First Impression: 2019 KTM 300 XC-W TPI

It’s human nature to want technology to save us from ourselves. We make progress, which leads to problems, which are fixed by progress and the cycle continues. With two-stroke dirt bikes, progress and advancement has been abruptly supplanted by four-strokes. They have taken over in both technological prowess and racing performance.

But on an alternative path of development, KTM and Husqvarna have continued to create technology for two-stroke engines, yet it isn’t performance and race victories they are chasing, it is passing emissions and keeping up with ever increasing European regulations.

The throttle body is only regulating the amount of air going into the engine - no gas, no oil.

The oil tank holds about a liter and is good for three to five tanks of gas depending on who you ask. There is a "low oil" light on the dash that lets you know when you have about a gas tank's worth of oil left.

Transfer Port Injection

KTM/Husqvarna has been clear that the TPI technology isn’t fuel injection as we think of it on a four-stroke dirt bike, yet there are some similarities. On four-strokes, the throttle body is controlling how much air and how much fuel from, depending on the bike model, one or two fuel injectors and that air/fuel mixture enters the combustion chamber together.

The TPI system takes a different approach by keeping air, fuel, and oil pretty much seperate. The Dell’Orto 39mm throttle body is only affecting how much air, via butterfly valve, is going into the motor. The oil is being added after that in the bottom of the engine, regulated by the ECU. Lastly the gas is being added by two seperate fuel injectors on both sides of the cylinder in the transfer ports, also controlled by the ECU. Fuel pressure is built by a single fuel pump feeding both injectors.

Cleaner Not Faster

No, we are not calling the bike slow, we are just pointing out that the TPI system was mainly developed to pass stricter emissions regulations in Europe, where KTM sells a ton of their two-strokes. The focus with this technology is a cleaner-running motor. It wasn’t developed by the racing department to make a faster or higher performing two-stroke engine focused on speed and winning races. All that being said, there is a certain amount of oil being sucked into the combustion chamber from the crankcase, it is just less than a standard carb two-stroke.

Since the oil is being injected into the motor without being mixed with gasoline, it is more effective at lubricating the bottom end, therefore less of it needs to be used. The crankcase never sees any gas, unlike a carbureted two-stroke, which has the gas/oil/air mixture pass through it. The ECU is constantly measuring how much gas and oil is needed, lowering fuel and oil consumption. This also means that the oil/gas mixture ratio is being adjusted by the ECU to match the motors real-time needs. If you are chugging along in tight terrain, it can be as low as 100:1, but if you are wide open blasting down a sand wash, it can adjust the mixture much higher to keep things cool and lubricated.  

We are hammering down the  for all the two-stroke mxers out there that are expecting to see this technology show up on the KTM 250 SX or Husqvarna TC 250. A representative at KTM said that there is no current plans to put the TPI system on their motocross bikes. He didn’t give specific reasons for that, other than, the TPI was never developed for racing purposes. We can also take into consideration that the system adds complexity that isn’t necessary on a track-only two-stroke, and it also adds about 7 lbs.

But There Are “Performance” Gains

While TPI isn’t trying to make a two-strokes faster, there are major plus sides to the system. The first… No more jetting! For those that don’t ride at different elevations, this isn’t so much as a problem. But when your off-road ride takes you to drastically different elevations or you live somewhere that has varied humidity and temperature ranges, the struggle is real to get a two-stroke tuned properly.

The TPI bike’s ECU is constantly monitoring the air pressure, temp, and other readings to keep the air/fuel mixture spot on. The ECU is also keeping tabs on just how much oil is need at all times. This leads to another plus; having separate oil and gas tanks. This isn’t so much a performance gain than a convenience gain. Even in states where you can get a plate for your two-stroke, grabbing straight gas at the gas station requires some guess work with the premix. With the TPI, you just throw in straight gas and go. The oil tank, conveniently “hidden” in the frame’s front downtube, holds about a liter of oil; enough for about five tanks of gas. KTM says three but most people we’ve talked to that has long-term tested says that three is conservative. Since you can’t see how much is in the tank, there is a low oil light on the dash. Once it is illuminated, you have one full gas tank’s worth of oil left.

How Does It Ride?

It’s been a while since we rode any 300 two-stroke, so a head-to-head comparison is stretching our memory a little thin. But, our main tester, Michael Lindsay, did have a chance to ride a 2018 250 TPI bike last year, and, while it was down 50 ccs, he noticed that the ‘19 300 XC-W we tested was not only more potent and torquey-er but it had more of that classic two-stroke hit that was lacking in the 250 TPI bike.


Now, its power delivery does feel a bit more linear, a little more smoothed out than typical two-strokes, but this made it extremely easy to ride off-road and we were able to ride it more consistently for a longer period of time over a large variety of terrain without getting wore out. Also, the bike is sneaky fast. Meaning, since the latest generation of KTM two-stroke engine has nearly zero vibration, and the exhaust note is responsibly quiet, the 300 XC-W feels and sounds mellower than it is. Once pointed up a soft, steep climb, that 300 two-stroke power was like cheating. If you have the skill, this bike can climb anything.

Throttle response is also quite exceptional - any throttle opening change created an immediate response in the rpm. Starting seemed even better than carbed two-strokes, not that they are slow to start, just that the TPI bike took like a split second to fire up.

The only con we can say about the 300 XC-W TPI is that the very bottom end of the power, where a few 300 two-strokes can feel super torquey and chuggy, the TPI feels a little thin. Not necessarily down on power, but more like it wants to be a little higher in the rev range than lugged right off idle. And this might not be a con for riders who prefer to rev out their two-strokes like a 250 or even 125.

Suspension

Right off the bat, front and rear is super soft, but we have to keep in mind that the XC-W models are aimed at the rider who spends most of their time in tight, technical terrain with baby-head rocks and endless labyrinths of tree roots. The 48mm WP Xplor fork, while being soft, does have adequate bottoming resistance when not getting too rowdy, and it offers great front end traction and a connected feeling from the front wheel. The Xpor for has a “split function” design where both fork legs have coil springs but the left leg has the compression damping and the right leg handles the rebound.

Also, the word “harsh” is the not in this bikes vocabulary. The WP Xplor shock matches the front in plushness and traction. Some riders find the PDS shock (no linkage) to have stink bug stance but with the sag set for our weight, we didn’t really have that issue. There is a second piston which kicks in at the end of the stroke to create a progressive damping feel, matched with a progressive shock spring. It really does have a similar feel to a linkaged bike, with the benefits of no linkage - lighter and more ground clearance.

We didn’t have the bike long enough to get deep into suspension changes but in the past we have ridden some bikes with the Xpor suspension that we got good hold up out of. Just know that if you are going to be riding this bike on fast or flowing trails, or any terrain with rollers and whoops, you’ll either have to slow down or do some suspension work. For the slow gnarly stuff, your golden.

No linkage here.

No-Mix of the Future?

We don’t have a crystal ball and, frankly, we aren’t thinking that regulations in Europe or in the US are going to ever get more lenient. TPI is pretty awesome technology for the average rider who is just trying to get the most out of riding a two-stroke off-road. And yes, you could race this bike no problem, that is, not at the pro level. But who of you out there really is at the pro level? We planned on racing it at a District 37 Sprint Enduro before a thumb injury sidelined us.

It’s pretty clear that this technology is a step in the right direction but it isn’t the final word in a “clean running” two-stroke engine. What is also clear is that TPI technology doesn’t really make sense for motocross bikes, since you’d be carrying more oil than you’d need, more weight, and have more things that could go wrong in a 20 minute moto.


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