The Yoshimura RS-4 exhaust system claims 3.5 per cent more horsepower than stock as well as 1.5 per cent more torque while being 11 per cent lighter.
We were searching for a bolt-on exhaust system that would boost the power of our Suzuki RM-Z450 long-termer. Suzuki and Yoshimura have been matching up for some years so it was only natural that Yoshi was our first port of call.
The RS-4 exhaust system claims 3.5 per cent more horsepower than stock as well as 1.5 per cent more torque while being 11 per cent lighter. The header and muffler are both made from stainless steel but the silencer end cap is carbon-fibre.
The muffler features a two-stage baffle and pentagonal sleeve while the front-end of it functions as a poly-resonant chamber that helps reduce noise. We bolted the pipe up and gave it a flogging for a few months to see how it held up.
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EASY TO FIT The Yoshi pipe goes on really easily. There are no tricky bits in fitting it. If you know how to use a socket set and a spring puller then you will have no problems bolting up the RS-4.
POWER BOOST The increase in power is dramatic. The standard pipe is very restrictive and not only muffles the noise but strangles the power. The increase in torque as well as throttle response and bottom-to-mid power is very welcome.
APPEARANCE It’s no secret that the stock pipe looks like a giant bazooka hanging out the back of the RM-Z. The stock muffler is excessively long but the Yoshi pipe is much shorter and looks much neater behind the sideplate. The carbon end cap also adds a little bit of flair to the pipe.
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HEATSHIELD The only issue I had with the pipe was it didn’t come with a heatshield for the header. It has the mounts for one but you must remove the stock heatshield and fit it to the Yoshi pipe. This isn’t the biggest of issues but anyone who has had to remove a heatshield after moisture, heat and dirt have done their work in the threads knows the frustration.
VERDICT
The Yoshimura RS-4 exhaust system had everything I was looking for. It increased power in all the places I wanted it to and improved torque to really allow the RM-Z engine to release its full potential. It was easy to fit, produced a nice note and looked stylish on the bike.
Not once did it come loose or cause any issues. It is made from robust, quality materials and stood up to everything I threw at it. It never let me down once so, for this reason, I feel completely comfortable recommending the Yoshimura RS-4. Technical Editor Mat Boyd
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BILL: $999.94
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