Fine-tuning the injected two-stroke off-roader

 The popularity of the KTM 300 XC-W TPI machine revolves around its clean power—a smooth exhaust of tractable muscle that erupts with a vibration-free throb that allows it to make traction. That is certainly why the world’s best hard enduro racers not only praise it but make it their go-to steed in tough events. There is no doubt that average riders are positively anemic compared to these racers, yet the 300 serves their needs with as much authority.

DB’s Tom Webb may be OTS (Older, Thicker, Slower) but the KTM 300 TPI machine has been a good marriage. All of the mods were done to make it stronger and easier to ride.

Over the last six months our 300 has traveled more trail miles than any machine in our stable. In the process, we have tested a bevy of products, mods and updates that any hardcore 300 flag-waver would embrace. Here’s a look at what makes life with the 300 XC-W TPI steed more palatable and empowers it to be one of the best off-road tools of the year.

SRT Off-Road is a huge supporter of off-road, both in racing and in focused products. Its Pro-Flo exhaust pipe is designed to be more durable than the stock chamber, yet offers smooth, consistent power. It’s made from 18-gauge carbon steel, is nickel-plated and comes with two O-rings for the header. This exhaust pipe is a beefy unit, weighing more than the stocker. SRT designed it to be tough but understands that if you make a pipe too stout, a blow that won’t compress it will actually tear the frame tabs right off the machine. The mounting and fit mirror the stock unit, though loosening the mounting brackets allows it to properly line up with the muffler. 

Our extensive field testing showed that the SRT chamber made for a nice upswing in roll-on power. The smooth character of the 300 is one of the critical factors in usable power, and the SRT Pro-Flo exhaust pipe gives it a little more pop. It is subtly stronger and very friendly. Moving into the midrange, the power remains very close to the stock powerband’s, and peak horsepower also feels similar. In two months of testing, we have yet to ding the pipe. We love the bottom-end strength and retention of usable thrust. Overall, we give the SRT Pro-Flo pipe a hearty thumbs up. 

Price: $209.99

The RK billet head is designed and manufactured in the USA. The two-piece design with an outer dome and a changeable inner dome allows you to tailor your powerband for the altitude you ride at via the alternate dome profiles. It utilizes tighter squish clearances and a narrow squish band, which will increase combustion efficiency and produce a more centralized push on the piston, thus increasing power. End gases aren’t trapped in the squish band where they can’t contribute to the power process. With a two-stroke, getting the proper compression is the key to usable thrust. And in the case of the KTM 300 TPI, an increase in compression improves bottom power. RK prides itself on the fact that its employees ride, and molding the powerband to work more efficiently off-road is a process that is critical to their passion for riding. 

We tested the RK billet head with the standard dome insert. This offers performance gains via the dome profile and increases compression, yet allows you to retain the standard ECU settings on the TPI machine. In the stock configuration, this machine tends to be a little rich down low and segues into a lean zone in the middle. With the RK head, we felt an immediate gain down low, making for more responsive power and the ability to short-shift and use a taller gear in technical terrain. Mid-power felt strong, and peak power was both stronger and meatier. We also tested it with a re-flashed ECU (from KTM) with richer settings. In this scenario, both the mid and upper power were stronger, allowing it to pull with more authority. The bottom line is that the RK billet head is a quality product that bolts up easily and makes for an immediate improvement in usable power. It actually makes the machine run cooler and is tunable via the dome inserts to perform in high-altitude conditions. 

Price: $325

In our constant search for a stronger yet meaty and smooth pull of power down low, we installed a Thunder Products torque wing. The torque wing is installed on the engine side of your throttle body. This divides the throttle body’s intake zone into four quadrants, utilizing horizontal and vertical air stabilizers. The horizontal and vertical wings target the elimination of air turbulence, which increases air velocity to the engine. With a throttle body that uses a butterfly valve, a half-opened throttle has the butterfly opening working as a virtual wall that blocks incoming air. The torque wing is designed to enhance flow, directing the air up and through the butterfly flap. 

The installation is not a knee-slapper. You must remove the throttle body from the machine, then make two small cuts in the neck of the opening at 12 o’clock and 6 o’clock that accept the lock tabs. There are also locating tabs that you must bend and shape to fit into the throat of the throttle body. We were nervous nellies using a hacksaw on our throttle body, but in the end, we got it located, set and fit in where the internal cutaway runs close to the opening butterfly valve. 

We were impressed with the improvement in the feel of the powerband. It’s stronger—not in the hit, but in the flow from roll-on to the middle meat to the band of usable power. Short-shifting and throttling down to make traction in tricky terrain is much easier. Overall, the Thunder Products torque wing gives our 300 one more weapon in the search for usable tractable gains in bottom-to-mid power. 

Price: $125

Originally, we had two maps for our GET ECU that Slavens Racing set for us to work in conjunction with its S3 high-compression head. We had a performance setting and a traction mode for smoother power in technical terrain. In the power mode, we were happy, though it tended to be rich and lethargic as the altitudes got up to the 6000-foot level. Here, the second mode for traction was too rich. Since we spend more riding time in the summer at higher altitudes to escape the heat, we needed something that would work from 5500 to 7500 feet above sea level. Slavens sent us a new GET unit with updated maps installed. The full power mode has changes to the fuel and ignition timing, making for an all-around gain in the muscle to the powerband from top to bottom at 3300 feet of elevation where we normally ride. The second map, switchable at the bars, was our high-elevation map. 

You can program your GET ECU with the WI-FI module.
You can program your GET ECU with the WI-FI module.

This unit has an app and Wi-Fi connector that allow you to make changes any time; although, to be honest, we’re not confident enough to calculate the proper settings that will work for us. This is where Slavens Racing came in and programmed the new settings. You still have to reset the TPS on the machine with the GET app and Wi-Fi module. It’s a detailed procedure but doable when you follow the instructions properly. 

You need to reset the GET ECU using the dongle that plugs into this connector.
You need to reset the GET ECU using the dongle that plugs into this connector.

Our second setting was a high-altitude map that proved to be phenomenal for our higher-elevation riding zones. Power here suffers, and even with the stock EFI machine, it gets to be a challenge as the power gets thick and tends to want to load up (though it’s substantially better than a normally carbureted machine). With the new Slavens map, the power was crisp and broad, and allowed the machine to still short-shift and lug in zones where obstacles demand smooth, clean power at our normal riding elevation. The high-altitude mapping was brilliant and a game-changer when the air got thin. This gets a big thumbs up.

We have documented that there are certain areas where the standard 300 XC-W TPI machine is lacking. One of them is standard mapping, which is a little rich down low and lean through the middle of the hard-on-the-gas throttle. We know that for 2020 KTM has addressed this with new mapping, and targeting stronger and meatier power. Our contact at KTM got us to send in our ECU so they could remap it. This is something that any owner can do by going to his or her dealer. This mod offers an immediate performance gain, giving the 300 stronger mid-power and the ability to pull harder on big loads, such as a long sand hill-climb. It also works perfectly if the owner adds compression, be it through head mods or an aftermarket head fit with a higher-compression dome. It is labeled as MAP updates, or Sport rider MAP.

Price: N/A

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