RATH RACING YFZ300 XC 2-STROKE HYBRID

RATH RACING YFZ300 XC 2-STROKE HYBRID

Big-bore, fuel-injected two-stroke racer

Taking the heart of the KTM 300XC and transplanting it into a YFZ450R chassis, Rath Racing has created a four-wheeled masterpiece with  smooth power for J.D. Higgins to take GNCC racing. 

WHAT DOES IT TAKE TO SWAP A YFZ450R FOR A KTM?

While one might expect such a swap to be complicated, fitting the KTM 300 two-stroke into the space created for the much-larger YFZ450R leaves ample room. However, getting angles and positions correct is another matter entirely. Rath Racing made a seamless solution with custom anti-vibration motor mounts without cutting or modifying the frame. This trick build could be returned to its Yamaha beginnings if needed. 

To say anyone could swap a KTM 300 into a YFZ would be a stretch, but even fewer could do it as cleanly as this. The build was designed for racing in the woods at GNCC events. It uses the standard YFZ450R airbox with a BNR Motorsports intake that’s been lightly modified to fit on the KTM two-stroke EFI throttle body. The exhaust system is a custom work of art from Trackside Performance using the stock KTM muffler. Rounding out the drivetrain, Rath was still experimenting with gearing ratios at the time of writing, but was close to a solution that adapts to four wheels.

GETTING CREATIVE

With the engine swap, Rath Racing made a significant effort to maximize the fuel capacity of this build. They installed a custom aluminum tank that took plenty of trial and error to make the most of the confined space. From custom lines to seemingly random choices for certain parts, this fuel tank was optimized to the nines. 

The fuel pump comes from a KTM 450, because the KTM 300 OEM fuel pump would only work with the stock dirt bike tank. This led to some interesting geometry at the top of the fuel tank and required a lot of custom-fitting effort. Ultimately, a fuel line from a different KTM model and some repurposed radiator hosing came together to maximize fuel capacity for cross-country racing.

POWER TO THE GROUND!

Rath’s work on the rest of this monster could be best described as race preparation. The front end got Walsh XC A-arms with LTR geometry and custom Axis shocks. The setup is tailored for trail riding and GNCC racing, a feat that comes with high expectations. A Walsh anti-vibration steering stem was also installed, buffered by a Precision steering stabilizer. This setup helps everything feel light and responsive with a width of 47.5 inches, which is optimal for tight woods racing. At the rear, a Rath Hybrid swingarm was custom-built just for this application. 

Keeping this power in check is a set of 6-ply Obor Advent tires with aggressive cross-country grip. The tires are wrapped around lightweight Hiper beadlock wheels. The front brake calipers are stock Suzuki LT-R with Baldwin Motorsports spindles, while Honda TRX hubs are mated with a LoneStar Racing axle at the rear. 

RATH RACING YFZ300 XC – HOW DOES IT RIDE?

This setup was built and tuned to be a veteran racer, and it shows. The power from the KTM 300cc two-stroke engine that now calls this YFZ chassis home is strong from idle to top speed to the point that Daryl Rath described it as “almost too much.” In a head-to-head drag with a conventionally built GNCC YFZ450R, it’s at least as fast, if not a bit faster.

The roll-on power in the bottom end, combined with this KTM engine’s mid-range, makes it an absolute animal in tight woods, which is what it was designed to be. When others have been given the chance to feel it for themselves, they always respond, “I can’t believe how good it is!”

The Rath YFZ450R/KTM 300XC swap is undoubtedly impressive, a match most sport quad junkies dream about, but what is even more remarkable is the level of fit and finish. The swap feels more like an OEM master design than a less refined hot rod. Down to the custom-made motor mounts, everything about this swap is something Rath says could be sold as a swap kit, which is truly incredible considering what the build is capable of. This is excellent news for the “save sport quads” crowd! It’s something worth looking out for in the GNCC later this year or early next year, and while most likely won’t be jumping to buy a sacrificial KTM, it’s undoubtedly destined to turn heads in the woods.

RATH RACING YFZ300 XC