There are more reasons to fit an aftermarket exhaust to your motorcycle today than ever: to hear your engine, cut weight, improve the design, and, in most cases, add better performance. Euro 5 and all of its buddies, Euro 5+ and now Euro 6, are slowly making their way deeper into our ECUs, making it increasingly difficult to have a bike that sounds good, looks good and fuels correctly. In fact, from my experience riding almost every new test bike that comes through ZA Bikers, it feels like some bikes are fuelling worse from the factory than ever before. That’s obviously my personal opinion, but it’s also why my view on flashing an ECU or fitting a slip-on exhaust is generally positive, provided you’re using a premium brand.
One of those exhaust manufacturers is Yoshimura, and if you haven’t already heard, Yoshimura exhausts are back in South Africa thanks to Sparx Distributing. We’ve already dipped a toe into Yoshimura’s history, what the brand stands for in the world of performance and racing, and the ethos and legacy behind it. But for me, that really started to sink in when I got my hands on the physical product. Ironically, it wasn’t until Steve Theron from Sparx Distributing sent me a Yoshimura RS-4 system for my Husqvarna Norden 901 that I truly appreciated what makes the brand so special.
We know the reputation, and that should be enough to justify spending your hard-earned money on a premium exhaust, but Yoshimura goes as far as packaging the product almost as well as it manufactures it. Unboxing the RS-4 made me realise that the passion really is in the DNA, from the well-packed box to the labelled bags of parts, including the tools for fitment and even some stickers to brand the back of your bakkie or laptop, for those special fans. I’m a die-hard nerd for these kinds of things; especially with my mechanical workshop upbringing, it’s just something I appreciate seeing.
Built for the Bike
Back to the RS-4, this is one of Yoshimura’s off-road-focused designs, and you’ll see it on Motocross, Enduro, Cross Country, Dual-Sport and selected Adventure bikes. It’s definitely not a one-size-fits-all kind of product, something you see all too often in the industry these days. Yoshimura focuses on designing each exhaust around the individual motorcycle, not simply changing the obvious link pipe and exhaust hanger, but also the length, shape and exhaust cone design. To me, that’s impressive. It shows how much effort a manufacturer is willing to put into essentially re-engineering an exhaust not only for a specific discipline, but for a specific model. That takes serious R&D, but for us riders, it showcases a commitment to producing something far superior to your run-of-the-mill aftermarket pipe.
The adventure-style RS-4 also has a distinctive off-road look, with its high-rise, MX-style design. I hate it when manufacturers suggest a certain accessory partner’s exhaust as an OEM fitment extra, only for it to look like some generic road or race-bike design bolted onto an adventure bike. I won’t name brands, but there is one that’s very good at making adventure bikes look like grocery-shopping SUVs with its exhaust design. Ok… Rant over!
KTM’s legendary LC8c parallel twin has been a winner since it came out in the original 790 Duke, and since then, no matter what package it’s found itself in. We’ve seen that same engine grow from 790 to 890 and now 990 cc, while moving from the Duke into the Adventure, SMT, Norden and now the RC R. It’s known for many things, but most importantly, its characterful midrange grunt and top-end hit make it a fun package enjoyed by all.
Of course, emissions regulations have played their part in the evolution of modern engines, with manufacturers having to find ways of maintaining performance while meeting increasingly strict regulations. Luckily for KTM and Husqvarna, their bikes haven’t been quietened down quite as much as some others, but the factory exhausts have still become bulkier and, in my opinion, uglier.
Living With the RS-4
So, out of the box came the RS-4, and I was keen to get it onto the Norden 901 as quickly as possible. On the home scale, the Yoshimura weighs around 700 grams less than the OEM muffler at 3.4 kg. That’s not a huge savings, but saving weight was never my reason for looking at the RS-4 in the first place. I was looking for a premium slip-on that looked at home on the bike, sounded good and actually added something to the overall package, almost becoming a feature of the motorcycle itself. The RS-4 does exactly that, with its carbon end cap and upper carbon exhaust shield, Yoshimura laser-cut mid-pipe cover, Yoshi-labelled exhaust spring rubbers, and beautifully brushed finish.
Fitment took me roughly 20 minutes, and it didn’t take much fiddling to get everything together. With all the required hardware and tools included in the box, it was refreshingly simple.
So, how does it sound? The typical small-block V8 character that comes from the LC8c has been enhanced, with a deeper low-down rumble, slightly more midrange pull and a lovely, subtle pop on overrun. It also sounds amazing when shifting right through the rev range with the quickshifter, giving it almost an Australian V8 Cup Car feel with that crisp sequential-shifter bark. Again, it’s not loud, but subtly enhanced, and if I had to put a rough, non-mathematically-correct percentage on how much more noise it makes, my best guess would be around 10% more. So, do with that as you will, but for me, it’s a good balance before the bark becomes bigger than the bite.
Does it make more power? Yoshimura claims the RS-4 slip-on provides a 5.5% increase in maximum horsepower and a 4.7% increase in maximum torque over the standard pipe. I haven’t dyno-tested my Norden, so I can’t independently verify those figures, but it definitely feels like there’s a little more in the bag. Obviously, if I were willing to go down the decat route with a new map and air-filter upgrade, we could be looking at more substantial gains. But if you’re looking to keep your warranty, retain some “OEM-plusness” and add to the overall look and sound of your Norden or KTM 790/890 Adventure, I think the Yoshimura RS-4 is hard to beat.
The Yoshimura RS-4 isn’t a cheap exhaust, and how can it be with all the R&D that’s gone into it? What it is, though, is a premium exhaust at around R23,000, and one that I feel looks the best on the Norden 901. Premium bikes deserve premium pipes.
For more information, visit your local motorcycle accessories store or contact the importer, Sparx Distributing, on +27 72 912 4658 to find your nearest stockist. Alternatively, contact Steve directly via email at [email protected].
