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Yoshimura’s goal was to add bottom end performance and over rev of the 23/24 KTM 350 SX-F engine character. On the dyno the new RS-12 TI system adds 2.7% max power and 2.6% max torque, but its not just about the numbers on the track is it? This new system is one of the few Yoshimura production motocross exhausts to incorporate a resonator on the header and in the muffler. The new header resonator can unlock bottom and midrange power to not only make the new Austrian bikes more powerful, but provides more rider connectivity. Yoshimura uses only premium titanium alloy tubing imported from Japan. Using titanium keeps the system light at 7.9 pounds and gives it that “works” look that is so sought after. The RS-12 asymmetrical shaped muffler allows maximize capacity and incorporates a resonance chamber for managing sound and increasing usable power. RS-12’s unique profile also provides more clearance for tire and brake caliper.
Just like the works systems that Yoshimura’s factory racers use, RS-12 systems utilize precision machined joints. Machined joints provide a superior and exacting fit for joints by better securing the seal between two surfaces with a perfect 360 degree contact surface which translates into improved system life, fit and performance. Works-look matte carbon fiber end cap is something different and to me sets the muffler apart from other carbo end cap muffler users.
On the track the Yoshimura RS-12 system increases bottom end pulling power out of corners yet without that snappy low end rpm response. I do miss that crack of the throttle with the stock muffler but the gain I get with the RS-12 out of corners is a welcome feel and actually allows me to get into third gear sooner so that kind of makes up for the loss of low end RPM response feel. Sometimes as riders we mistake low end rpm response with bottom end pulling power. The seat of the pants low end rpm response can hypnotize riders thinking they got excitement but that is not always the case. The Yosh delivers it’s power a little smoother than stock but has more torque feel in 2nd and 3rd gears. Mid range delivery is also increased and to me just pulls cleaner than the stock system. I like that there isn’t any mapping changes needed for the RS-12 and no de-el popping was apparent when swathing the Yosh system. Top end feels as good as stock but no increase of top end/over-rev was felt between the stock and Yosh systems. You will lose almost 1.5 pounds over stock so that is an added bonus. I also gave Eric Phipps from Works Connection the RS-12 to try on our 2024 KTM 350 SX-F test bike that was equipped with a FMF 4.1 and XPR tuned Vortex and below was his opinion.
My first impression of the Yoshimura Titanium exhaust system (full system) is that it is a work of art! The craftsmanship, welds and overall appearance are a 10. When installing the system on the bike, the fit is good and installation was easy. I did have to wiggle the head pipe around a bit to get the hole lined up with the frame mount, but overall the installation process was very easy. I have been running an FMF system previous to installing the Yoshimura and the Yosh pipe is slightly quieter and had a good tone. The bike also has a Vortex ECU mapped by (XPR Motorsports), and I used power map 1 like I did before so that the comparison would be apples to apples. The Yosh exhaust spread the power out but seemed to not quite have as much top end power as before. The power down low was very good and led into a meaty mid-range though and the power was easy to use. I was running the insert also, so that may have had an impact on slight lack of top end power. -Eric Phipps
Ease of installation: 10/10
Fit: 9.5/10
Appearance: 10/10
Power: 9.5/10