First look at the all-new SmartCarb SC3 arrives lighter, simplified, and with fresh options for smaller engines – it’s "the one they’ve always wanted to make," says Nathan Dyess from the U.S. manufacturer.

SmartCarb first came onto the Enduro21 radar nearly a decade ago. Ironically, this was a time when two-stroke off-road bikes were starting to feel under pressure – particularly those built in Europe for enduro – due to emissions regulations. It was also a period of change, with fuel-injected Austrian bikes becoming a dawning reality.

At the time, we asked of the SmartCarb: “Don’t we need this kind of technology to keep us going?” The answer was sure we did, and we still do, as two-stroke dirt bikes remain a massive part of enduro and continue to benefit from; “the most advanced mechanical fuel system available today for off-road and racing motorcycles.”

Helped in part by Cody Webb, ahead of his new venture onto Yamahas, the SC3 has been in development for over a year and has included race testing in the US Hard Enduro series.

Now updated to its third generation, the SmartCarb SC3 model retains its impressively broad remit – not just for enduro and motocross but essentially for anything with a carburettor (including Yamaha Banshees, BMW airheads, trials bikes, karts, aircraft, snowmobiles – you name it!).

To get a better understanding of the new SC3, Enduro21 reached out to Nathan Dyess at SmartCarb. He explains why increasingly compact engines and chassis designs mean the new model hard to slim down and why both amateur and professional riders are at the core of their product development.

SC3 Technical Highlights:

• Family of SC3s ranges from 36-40mm plus 26 & 28mm 
• New CloudForge™ Venturi | Optimized signal generation and fuel atomization
• Moisture Management | Improved throttle control in extreme humidity
• Larger Vent Scoop | Faster float bowl venting communication
• Blended Slide Cutaway | Cleaner off-idle throttle response
• O-ring Float Bowl Gasket | Improved sealing and sleeker look
• Doubled Fuel Rate | 2X fill passages for quicker float bowl filling response
• “Tucked” Fuel Fitting | Improved fuel line routing
• Crisper Clicker Haptics | Improved clicker feel
• Complete Design Overhaul | Better fitment with smaller form-factor
• Mirrored Option | Right Hand (RH) and Left Hand (LH) configurations available
• Reduced Part Count | Cost savings passed to our customers
• Lighter Weight | 12% reduction
• Smaller 26 & 28mm SC3 option has single piece unibody design

Can you tell us the main aims or design brief with the SC3?

Nathan Dyess: “The SC3 is in many ways the SmartCarb we’ve always wanted to make – the ultimate distillation of what makes a SmartCarb a SmartCarb and that is, in a word, simplicity. We really had to (got to :) get creative in building upon everything good about the SC2 while asking ourselves “is there a cleaner, simpler way to do this?

“The most obvious change we made was, hands-down, to the little carbs (26/28mm). They’re now a unibody design using a single piece of aluminum for the main body piece. That alone cut 12 parts out of the assembly while allowing us to adopt best carburetor practices like rubber o-ring float bowl gaskets.”

“Aside from going as simple as possible we did have a few things to improve with the new SC3 based on feedback on the SC2. One is fitment. Carbureted bike seem to be getting tighter and tighter, particularly with the Betas (our top bike make equipped by far). The SC3 is shorter end-to-end, top-to-bottom, and the rounded corners really help with clearance (not to mention appearance).

“Lastly, we’ve always felt a need for mirrored configurations as we expand into new markets. So the SC3 comes in a Left Hand and Right Hand option for applications like Yamaha Banshees, BMW Airheads, and more. The Right Hand 28mm SC3 will really help us dive into the Beta EVO trials community in particular.”

How long has the SC3 been in development?

“Well, we had our wish-list started for it pretty much the day after launching the SC2s back in 2019 but I would say serious development began in January of 2024 or around 14 months ago. Testing in-house, via trusted long-time customers, and more recently with some of our high-level sponsored racers has been invaluable toward delivering a 100% ready product. Fun fact: the 36-40mm SC3s launched on their 6th internal design revision.”

Normally new products are more expensive, how on earth did you manage to make is LESS money?!

“Right?! In today’s world? It all goes back to simplicity. Reducing part count, working with our machinists on clever ways to reduce machine time, hunting down alternative suppliers without any reduction in quality all played a role in our ability to pass along savings to our customers.

“We’re proud to make SmartCarbs in the USA and so that was non-negotiable, but machine time here can be quite expensive. Fortunately, we’ve been able to link up with a new mix of shops that are more our size and that are, critically, more flexible. Our POs will lock up multiple robotic palletizing mills 24/7 for months at a time.”

In terms of Enduro/off Road: Is it applicable to all kinds of riding and racing from hard enduro to trail to Cross Country?

“Absolutely and we’d go beyond that to add in MX, trails, supermoto, snowbiking – and that’s just motorcycles, right? We’re also selling to scooters, paramotors/light aircraft, an increasing number of 4-strokes, and more.

“But to your question yes, the SmartCarb SC3 is suitable for all riding styles which is why that is one of 4 questions we ask from each and every customer. We factor it in when we pre-tune their SC3.”

All other well-known positives (like fuel efficiency, no spill, no complicated set-up) remain, right?

“Oh yes, we don’t believe in stepping backward on anything. The SC3 retains all of the same function and benefits including performance, efficiency, and ease of use that the SC2 is well-known for. That said we have made some significant updates beyond simplification of the design and improved fitment.

“The 36-40mm SC3s get what we are calling the CloudForge venturi profile and without going into a bunch of math it essentially lofts airflow differently at low throttle positions, boosting signal at the metering rod which is critical for fuel pick-up and atomization.

“As you may know our competitors seem to keep adding additional circuits and power jets to work around what we believe to be signal deficiencies. SmartCarbs are the only single circuit fuel system made today but to do that right requires very purposeful shaping of the venturi as well as integrated float bowl venting.

 “Speaking of venting, the SC3 gets a larger vent scoop, catching a bit more airflow that it uses to drive fuel flow – especially at higher throttle positions.

 “Before leaving Sherco to join the Blu Cru, Cody Webb was instrumental in testing different slide cutaways in the SC2s in his 300 SEs and so the 36-40mm SC3 comes with what we call a blended slide cutaway that cleans up the off-idle transition nicely.”

Thanks Cody!

Who makes cheaper products these days?!

Literally a smarter replacement for your stock carburettor, a SmartCarb has always boasted tool-free tuning, better fuel consumption, power and emissions than a conventional carburettor. In our experience, put simply, a SmartCarb makes life easier and our two-stroke better (our YZ250 has an SC2 fitted).

The new SC3 promises to take things to a new level with improvements including cleaner off-idle throttle response and better performance in humid conditions, better fuel line routing, lighter overall weight and, thanks to design simplifications, reduced part count, and improved supply chain, is available for $100 less than the SC2. In this day and age what on earth costs less when they make a new version?!

Colour anodised options available soon. 

Configure an SC3 for your bike for prices and more information: www.smartcarb.com

Photo Credit: Sky Pixel Media and Jenny Keller (Quinn Wentzel image)