Aftermarket exhausts are almost a must-have item on any competitive bike these days, and our Project Moto 2013 RM-Z250 was no different.

Serco hooked us up with a Yoshimura RS-4 full system for our bike and we’ve put it to the test, read on to hear what we thought.

Yoshimura’s RS-4 full system was a great addition to the MotoOnline.com.au Project Moto RM-Z250. Image: Alex Gobert.

Technical Information
The Yoshimura RS-4 stainless steel full system was designed with one thing in mind – winning races. The RS-4 is a unique design with predicated power and a side benefit of a quiet earthy exhaust note that speaks volumes for performance.

The full system comes with a stainless steel header and mid-pipe, aluminum muffler sleeve, carbon fiber muffler tip, installation hardware, and step-by-step instructions. An AMA-approved sound insert also comes installed in the muffler.

Positives

One of the more common modifications you will see in the pits is the addition of an aftermarket exhaust. Most riders will ditch the stock system within days of taking delivery of their new ride, but it’s important to be sure you are actually making power gains, not just making noise.

For our Project Moto 2013 Suzuki RM-Z250 the guys at Serco provided us with a Yoshimura RS-4 stainless steel full system, complete with a super-cool carbon fiber muffler tip. That carbon-fiber tip brings a factory-look to the bike and really makes this exhaust a beautiful piece of hardware.

Fitment on the Yoshimura RS-4 system was a breeze. The product came with all of the necessary mounting hardware and the instructions were straight-forward. Those features are only small, but they’re things that will make life a lot easier for you guys working on your own bike at home.

Firstly, the note it puts out is very impressive. The bike sounds deep and throaty, but it also puts out a nasty bark at high rpms (click here to view the latest Project Moto film and hear the RS-4 in action). I must mention that we had removed the spark arrestor/sound insert that came on the exhaust before hitting the track.

Power-wise, I noticed a stronger pull throughout the rev range, but it was the mid-range that really benefited in my eyes. The RM-Z250 had that extra edge over the stock system, some more meat in the mid-range area to pull through corners and up hills.

On the RM-Z I was using the stock ignition coupler on the bike while running the Yoshimura RS-4 system. I preferred the power curve using the stock setting, the more bottom to mid-range power, the better for me.

The header section of the Yoshimura RS-4 exhaust. Image: Alex Gobert.

Negatives

My only negative comment on the Yoshimura RS-4 system is the decision to re-use the stock heat shield on the header pipe. Obviously they wanted to keep safety in mind with this design, but really, it just doesn’t look that impressive from a visual standpoint. That’s really what it comes down to in the end.

Verdict
We’re very impressed with the Yoshimura RS-4 system. It sounds great, performs even better and really makes your ride stand out with that trick carbon fiber muffler tip. The Suzuki RM-Z250 Yoshimura RS-4 system retails for $679.95 and you can check out www.serco.com.au for more information.