We started our trail build with the last 300XC model to come equipped with a carburetor: the 2019 KTM 300XC. This machine was fairly well-received by the carbureted community as a whole but did have some issues. One major issue was the constant need to modify jetting specs in the Mikuni unit that came on the bike stock. KTM had fought this issue since changing to Mikuni in 2016, making niche carburetor companies like Smart Carb and Lectron very happy. Keihin carburetors were standard issue before that, and we are still scratching our heads at KTM’s decision to change.
For this build we started with what we know works—a Keihin 38mm carburetor dialed in with a JD jetting kit. Internally, Tom Morgan Racing made some modifications to the head, giving it a slight bump up in compression, and installed a Vertex Pro Replica piston kit. Our goal was to get a little more grunt right off the bottom, like the new fuel-injected models, without losing midrange and top-end power. An FMF Gnarly pipe with a platinum finish and an Erzberg Factory 2.1 silencer were also added for some additional performance. The blue-anodized finish is just a bonus in the bling department. The last two internal engine modifications included a Moto Tassinari V-Force reed cage and Hinson Racing clutch components for some additional wear protection.
The 2019 300XC model received significant updates chassis-wise, basically getting the frame, styling and suspension updates that came the previous year to all four-stroke models. Race Tech did a service and re-valve, setting up both ends of our XC. One universal gripe about XC models on trails is the WP air fork’s harshness on small stuff. Since Race Tech is an authorized WP service center, we decided to go one step further and add a WP Pro Components Cone Valve spring fork. This was a large investment, but since this bike was primarily going to be used off-road on single track trails, we decided to see if spring forks are better than air forks once and for all.
With engine performance handled by Tom Morgan and the suspension under control thanks to Race Tech, our attention was focused on items that would make our XC more trail-worthy. We installed a rear fender and support off a 2020 XC-W model, along with a complete headlight assembly. The nice part about this is the headlight plugs right into the 2019 XC wiring harness, unlike with the 2020 TPI model. Another item that comes in handy on the trail is a Trail Tech radiator fan.
As with the headlight, installation was easy because the 2019 XC model features a direct plug-in for the fan as well. IMS Products makes a couple of items we used on this build. One is very noticeable, and the other is hidden inside the frame. The larger IMS tank holds 3.0 gallons without being any wider that the OEM tank. Losing coolant on the trail is not an option, so the engineers at IMS designed a coolant recovery system that mounts inside the main down spar of the frame right above the “Y.”
From here on out, it was all about protection from the elements. P3 Carbon’s full-coverage skid plate and pipe guard offer huge amounts of protection and add major style points to the build. We used Enduro Engineering’s new wraparound hand-guard system with orange EVO2 replaceable plastic deflector shields and clutch slave cylinder guard. TM Designworks has been seen on off-road factory bikes for years for one very good reason: all TM Designworks stuff works. The rear disc guard, caliper guard, rear chainguide and swingarm slider provide additional protection and more wear life, and the bright orange matched our color scheme perfectly.
We know fuel injection is the future, but is the future really now? Our 300XC trail project is a great argument for keeping the carburetor around for a few more years. The switch to a 38mm Keihin was a great decision. Once dialed in, it ran crisply and didn’t require any major internal changes, even with outside temperature fluctuations. Our Tom Morgan Racing head mods provided noticeable gains down low, so much so that we had to use the external power-valve adjustment to tone it down a little.
Testing the Race Tech air and spring fork setups back to back was definitely eye-opening. The WP Pro Component Cone Valve spring fork initial setting is hands down better than any setting we could get on the air fork. It just has a plusher and more rider-friendly feel, especially on small trail chop. For some people, having the latest and greatest technology in the form of fuel injection is a must; however, we are all smiles with the primitive technology that made this build a blast to ride. Long live the carburetor!