When you think of Yoshimura, you usually think of Suzuki, right? The race team did very well for years before the untimely demise of the LTR, and the names sort of go hand-in-hand. However, Yoshimura R&D makes exhaust systems and fuel tuners for a number of machines, including ATVs, UTVs, dirt bikes, street bikes, and even scooters. We had a thirst for performance, so we ordered one up for our resident YFZ450R, which is currently the hottest sport and racing ATV around.
The Yoshimura RS-2 full-exhaust system is made of stainless piping and an aluminum muffler skin with high-quality billet hangers and inserts. The headpipe and mid-pipe both feature a coated heat shield to protect your pants and legs from burns. The system comes with top-quality fasteners and installation hardware. The price for all this beauty is $595 in aluminum/stainless, $845 in titanium, and $395 for the stainless/aluminum slip-on system (without the head pipe). Installation is quick and straightforward, as it fits every bit as well as the stock exhaust.
After running a stock baseline on the track, we bolted up the RS-2 full system using Yosh’s PIM-2 fuel tuner and DATA Box to draw up a custom fuel map. Using a full custom tune on a track will give you the best fuel trims possible, and the PIM/DATA Box combination is easy to use and works extremely well. We will do a full test on the PIM-2 and DATA Box at a later date.
For the first few laps, the tuning was slightly off. Small hiccups in the powerband kept the YFZ from running as cleanly as it does in stock trim. Fortunately, after a couple hours of riding and stopping every 4–5 laps to download the DATA Box’s fuel mapping, we had a solid map that allowed the YFZ to run beautifully with the RS-2 full system.
Off the bottom, the YFZ seemed to make a bit more power with the Yosh pipe, but it could be attributed to better fuel tuning as well. It pulled into a meaty midrange, and the top end pulled much harder and longer than with the stock pipe. We spent most of our time with the motor in the upper midrange where we still had a few thousand rpm to play with before shifting. It was smooth, fast, and with the 96 dB standard spark arrestor, not too loud. The pipe yielded a strong performance gain, and when we tested it in conjunction with the Fuel Customs intake, the power increased even more. The throaty sound of the pipe gives the YFZ more attitude, which it deserves since it’s currently the fastest ATV in the Quad-X race series.