How do they compare?
We get this question a lot and understandably so. Both carbs use metering rods in lieu of jets and needles, and both manufacturers make similar claims in terms of performance, air density compensation, and ease of use. Understanding how they compare is the first step to making an informed decision on which one is right for you. In this article we’ll cover a bit of the history of both products and then provide an objective comparison.
First a little background. The history and heritage of the flat slide, metering rod style carburetor is one shared by both the SmartCarb and the Lectron. They even share the same inventor: the late, renowned carburetion expert William “Red” Edmonston. Red first pioneered the metering rod carburetor concept with the unique Posa-Fuel and Lake Injector in 1967 and 1971 respectfully. Red’s Lectron came to market in 1974 and represented a major leap forward for the technology with the addition of a float bowl and the use of a flat slide for throttling rather than the cigar cutter or guillotine style sliding venturi from before. After selling Lectron to General Motors in 1978, Red went on to further develop and refine the metering rod style carburetor, culminating with the SmartCarb in the early 2000s. Technology Elevated’s Chief Technology Officer and Founder Corey Dyess had the privilege of working with Red during his final years and has led advanced development of the SmartCarb, winning multiple patents for feature improvements over time.

Same inventor, same concept, same thing… right?
Nope! While both carbs use a metering rod and a flat slide to provide precise air/fuel mixture control and superior fuel atomization to that of conventional needle and jet carburetors, there are more differences between the two than are readily apparent.
Always looking to do things better, Red, and more recently Technology Elevated, have evolved the design over time by adding improvements and features to enhance the basic operating principles of the technology while also addressing the shortfalls and limitations of prior designs. The result is a fuel system that is substantially different from its predecessors, including the Lectron.
Venturi Profile
Like most conventional carburetors, the Lectron uses a circular venturi shape. The SmartCarb does not. Instead, it uses a patented “inverted egg” venturi shape. The thinking here is not unlike what backyard mechanics have been doing for years by oval/offset boring conventional carburetors – that is to change the rate of throttle opening through the range.
There’s more to it when it comes to metering rod carbs like the SmartCarb and the Lectron. Maintaining sufficient air velocity or “signal” at the rod is critically important for fuel pickup and atomization. Any loss of velocity or weak signal at the metering rod can result in loss of fuel pickup and poor atomization, translating into hesitation, bogging, or soft throttle response. The SmartCarb’s venturi profile is designed to focus airflow directly at the metering rod through the entire throttle range in order to maximize signal and promote fuel atomization. The Lectron’s venturi is not designed for this purpose and as a result is more prone to suffer from weak signal and soft throttle response, particularly down low or just off idle.


← Drag Slider →
It is important to note that Lectron has taken steps in recent years to improve this deficiency, especially with their latest HV and H-Series models geared toward the off-road market. Both the HV and H-Series Lectrons are tapered down 4mm smaller than advertised just behind the slide. Higher velocity yes, but at the expense of top end flow and performance. The SmartCarb, with its advanced venturi shape, offers no such compromises, providing strong, linear throttle response bottom to top.
Float Bowl Venting
Float bowl style carburetors require float bowl venting to work properly, just ask anyone who has ever had plugged or frozen vent lines. The Lectron, like more conventional carbs, vents its float bowl through external vent/overflow hoses that hang down in front of the rear wheel. The SmartCarb vents its float bowl quite differently – from inside the airbox via a scoop/port located in the top of the venturi bell.
This patented internal venting feature allows the SmartCarb to compensate for a much wider range of air densities compared to the externally vented Lectron.
Venting and airflow communication between the airbox and the float bowl applies a steady, equalized pressure against the fuel in the bowl that is proportional to air velocity and density inside of the airbox. Put simply, more dense, heavier air drives more fuel flow, less dense air drives less fuel flow, and air/fuel ratios stay consistent regardless of elevation or temperature changes.
Beyond better air density compensation, internal venting also provides for sufficient top end fueling in the SmartCarb without the need for a power jet. Although the original Lectron of 1974 did not have a power jet, all modern iterations of the design come with at least one or more power jets to provide enough fuel to the mix from mid to top.

No overflow hoses?
Where does the fuel go in the SmartCarb?
Fuel in the SmartCarb’s float bowl stays in the float bowl. One-way check valves in the vent passages allow air to flow into the bowl but they do not allow fuel to flow out. That means fuel remains in the bowl on steep downhills and even if/when the bike is laid down. The SmartCarb is a sealed fuel system with zero fuel spillage that has been EPA certified with the lowest evaporative emissions ever tested by a carburetor fuel system. Zero fuel spillage and superior, single circuit metering rod atomization through the entire throttle range gives the SmartCarb user unrivaled fuel economy gains and emissions reductions compared to the Lectron or any other conventional carburetor.
Making Adjustments
Unless you count the Lectron’s power jet as a jet (and it is), both it and the SmartCarb are jet-less carburetors in the traditional sense. That means no more brass to change either way! Adjustments are still required during initial tuning and to accommodate engine modifications, changing fuel selection, and in the case of the Lectron, when substantially changing elevations or for large temperature swings.
The Lectron has 3 adjustments: the idle set screw, the metering rod position, and the power jet. The SmartCarb has only two: the idle set screw and metering rod position. Changing the metering rod position in the Lectron requires removing the cap and pulling the slide. Lectron metering rod adjustments are limited to 4 positions per revolution.
Conversely, changing the position of the metering rod in the SmartCarb is done externally, by hand, and from the seat of the bike in most cases. The SmartCarb’s metering rod can be more finely adjusted with 10 clicks/positions per revolution by shutting the engine off, opening the throttle to wide open, and using the clicker adjuster in the cap. Adjustments take seconds and can be done while the engine and pipe stay up to temp.

With both the SmartCarb and the Lectron, metering rod adjustments will primarily affect the bottom end or the low speed. Metering rod mixture adjustments in the mid to top of the throttle range require swapping out the metering rod for one with a different grind profile, depending on fueling requirements. Both companies offer a variety of different metering rods for the fueling needs of various applications and can advise their customers regarding metering rod selection.
Compatibility
The SC2 model SmartCarb and H-Series Lectron are designed for use in modern 2-stroke dirt bikes and similar applications using the Keihin PWK or Mikuni TMX stock, however their build quality and manner of construction differ in a few notable ways that affect their appearance, compatibility, durability, and ease of use.
The cast aluminum Lectron, being a much older design, presents a few issues when used in modern applications including a longer end-to-end length (.25″/6mm longer than the SC2), stock throttle cable incompatibility, inconvenient choke placement, and no throttle position sensor (TPS) option. This means the fit in the tighter bikes can be tricky (Lectron recommends the use of the shorter XC-W or TE intake flange with the H-Series when installed into 2017 or later KTMs or Huskies), the stock throttle cable and handset must be replaced with ones provided by Lectron in most applications, the pipe side choke can be hard to reach, and the use of 3D ignition mapping, Beta oil injection, or aftermarket CDIs requiring TPS isn’t an option.

Forward Thinking
The SC2 SmartCarb is designed with the future in mind and is capable of meeting the performance needs and emissions requirements of the rapidly changing off-road powersports industry. They are fully CNC machined for precise tolerancing and increased durability, accept all modern stock throttle cables, and TPS is a factory option or user installable at any time.

Which one is right for you?
The choice is ultimately up to you. Our hope is that this article sheds some light on the history of these revolutionary fuel systems and that it offers a clear and concise explanation about their differences. Knowledge is power and an informed decision is a smart decision.
Stay tuned for a comparison video coming soon to our new YouTube Channel!
Hello my name is Robert, I live here Japan. I was thinking of purchasing a Lectron but you’re got my full attention. I have a ‘99 MBk Stunt(Yamaha Slider)vertical Minarelli, 2 stroke mods are: Most 70cc high end bore kit, Most racing exhaust, custom intake with V-Force 8reed, Pwk 28 carb (slow jet 48, main jet 145) . Spark plug is NGK BR9ECM the same that is used on NSR250 and no air box only velocity stack. Well nothing is stock anymore, it doesn’t even look like a Stunt, I do mostly street racing and either the throttle is closed or fully open. I use 100 octane pump fuel pre mix at 50 to 1 oil ratio, . What do you recommend and is it available? By the way, my sister live really close to you, your located in Raytow she lives in KC about 20 minutes from the KCI Airport. Thank you for your time, Robert Sasagawa
I hear one of your customers are testing a 38 mm on a BMW R100 RS with good results and I read the Ducati 900 article. Would you consider making asymmetric sets for BMW airheads and if so when might that be .. ?
Hi Niels, yes we’ve equipped around 5 R100s so far with great results. Asymmetrical or mirrored versions are coming but not likely until toward the end of the year.
Wonderful, I won’t be riding until March 15 anyway. Can you spill something about what “great results” means, dyno hp, economy and emissions? if you can post something on your site when ready, then I can make propanda for them maybe .. question: in the Smartcarb vs Lectron article your metering rod is shown, but I would like to see how the holes are made on it .. and what is the blue hose going from the bottom doing?
Sorry I overlooked the manuals says the blue hose at the bottom is just a drain. Is the BAC model, which subjectively looks better to me, also sold or just the ones that show on the Shop page? Are you planning asymmetric/mirrored versions for other two cylinder older bikes?
Hi!, I have a Banshee with 2-into-1 intake system (one carb for both cylinders). What do you recommend, 36mm or 38mm?
Hi Jose, we recommend the 36mm for a mostly stock Banshee with 2-into-1 intake. Are you using 1 or 2 pipes?
Hello looking to buy a 2015 yz85 FOR my son and would love info on WHEN you WILL have the carb BACK in stock
Dan
Hi Dan, we’re planning on having the 28mm size SC2 SmartCarb available in the coming few weeks. Send us an email at info@technologyelevated.com and we’ll add you to our list to notify of availability ahead of a general announcement.
What setting should I start with i have a smart carb 38 ca kn air filter and open air box v force 3 reeds?
Also its a Honda TRX250R 2 stroke.
Hi Lloyd, for a 38mm Cast model SmartCarb we would recommend the A-Q07 metering rod at around 45-50 clicks from full rich. Depending on engine mods and fuel selection, the step richer A-Q05 may be recommended. Any engine mods on this TRX250R? What fuel type and oil ratio are you mixing?
Tengo una yamaha dt200wr q me recomiendas de cuantos mm me recomienda el carburador SmartCarb SC2
Ok im currently Racing 45 flatheads and running Lectron.what do you have and Price! And any Sponsorship !
sir my motorcycle is 1999y cagiva mito 2 stroke street bike
can i use smartcarb on my bike?
it is for only premix dirt bike?
thank you
Hi Team SmartCarb,
I am planing to use your carb on my PX200 251cc engine. what size of the Smart Carb which i use it?
What about 4 strokes
1 . The SC can be used for 4stroke engine?
2 . I have suzuki v100 scooter ( 2 stroke )
can the SC be used on my motorcycle? what is the right size?
Was wondering about vintage bikes, I have an 81 YZ 465 and would a smart carb fit, the stock Mikuni 97 mm long and I don’t have a lot of height before it hits the frame . I live at 6500 ft elevation but go to around 500 ft and up to 9000 ft so no jetting would be real nice. Thanks for time. Dave
Can this work on my moped .. it uses a bing Carburetor
I have `17 TC125 running the 144cc top end. It is modded by Tom Morgan. He ported and adjusted the compression. Although I dont know exactly the spec changes he made (port height changes, squish changes etc).
What info do I need to get from him, for a SmartCarb to be properly set up?
I also run: V force reeds, ProCircuit pipe and shorty silencer and 32:1 pre-mix of 50:50 mix of 92octane non-ethanol pump to 110 Trick race gas which yields about a 101 octane mix w/ Maxima Super M.
FYI – Im currently running a JD kit, but it is not perfect. I still get an occasional bog off idle, or at a steep forward angle, despite using JD`s recommended settings as well as changing things around a bit.
and….will a SmartCarb for my TC144 be able to retrofit to a differing bike in the future such as a 2020 TC250?
Cheers.
Hi Robert, thank you for your interest in the SmartCarb for your Tom Morgan modified 2017 TC144. It would be very helpful to us in pre-calibrating your SmartCarb if you could gather the following information from him and also provide further information yourself: difference in compression from stock and what your current, best jetting specs are with the JD kitted carb. If Tom provided jetting specs for his mods they would be helpful to know as well. We’ll take that information and use it to set your SmartCarb up accordingly. Questions from us: how do you ride this bike, or what is your riding style? How would you plan to ride the TC250?
We recommend the 36mm size SC2 model SmartCarb for your 144, available here: https://technologyelevated.com/product/36mm-sc2-smartcarb/ We typically recommend replacing size for size but there are some notable exceptions, the 2017+ KTM/Husky 125s and 150s (includes 144 kits) being some of them. Our 38mm size is just a bit large. That said, and to answer your question about the TC250, the 36mm size we recommend will work very well for either your current bike or the 250 and it is by far our most popular size. For the 250 a 36mm or a 38mm are acceptable and either will be an improvement everywhere over stock, however the 36mm will prioritize bottom end snappiness/responsiveness as well as fuel economy gains. Choosing a 38mm for a 250 is done when the top end needs prioritized as it will extend the powerband and provide an additional 500-600 useable RPMs over stock (think pure MX, snowbiking, desert racing, etc).
Feel free to reach out direct over the phone or via email at our Contact Form (https://technologyelevated.com/contact-us/) for assistance. We are happy to help!
Do you set a baseline in the carb for the applciation? for example, I have a WR250 with a Gnarly Pipe and FMF turbine core?
Hi Franky, yes we do. Every SmartCarb is set up specifically for the application for which it was ordered. We ask for the year/make/model, what notable engine and exhaust mods you’re using, how you ride the bike, and what fuel type/oil ratio you’re mixing. That information gives us everything we need to know to select a metering rod and pre-calibrate the SmartCarb just for you. Most exhaust pipes and silencers don’t affect our baselines. Mods that have a bigger effect include head modifications, upped compression, porting, bore kits, etc. We hope this answers your questions. We recommend the 36mm size SC2 SmartCarb for your WR250, available here: https://technologyelevated.com/product/36mm-sc2-smartcarb/
I have a KTM 950 with vacuum slides do you have a replacement for these carbs?
Hi Art, unfortunately we do not have replacement down draft style SmartCarbs developed yet for the KTM 950.
I run a old school honda cr125 on a shifter kart
What’s your recommendation
Its ported with rlv r4 or r5 pipe
Carbon tech reeds stock bore boost port teflon coated flat top piston
Hey James, we’d recommend our 36mm size SC2 for your CR125 shifter kart. See it here: https://technologyelevated.com/product/36mm-sc2-smartcarb/ How is your fueling set up – are you running gravity or a pump and if pump, is it a pump-around system? Also what fuel/oil ratio are you mixing at? Need to know these answers to configure the carb properly.
Do you have one that fits the YZ125 2017 model…
and is it suitable for same bore machines like a 125.
Who in the UK is the dealer for your carb
Yes we do, the 36mm size SC2 is recommended for the YZ125. Can you clarify what you mean by same bore machines? For a 125cc 2-stroke the 36mm is typically the standard recommendation, though there may be exceptions. We would need to know more about the application.
We do not currently have UK distribution, however we are working to expand our dealer network throughout Europe, including the UK, over time. You can order directly from us or you might reach out to SIP Scooter in Germany or HTM Racing in Italy for availability. They are currently our largest European dealers.
What would you recommend for a 2002 polaris edge x 700 twin snowmobile
Will you make a coolant heated option for the snowmobile market?
We don’t currently offer a coolant circulating heater, however there are two aftermarket companies that make heaters specifically for the SC2 SmartCarb. PST (Power Sports Tech) and Avid Products both make press on or clamp on heater jackets for use in snowbiking. That said we have found with our extensive experience snowmobiling that carb heating isn’t normally required as they’re completely shrouded under the hood.
Have you been addressing the street bike market with this info? Such a big market out there…
It’s a huge market and the potential for excellent results is there as you well know with your SmartCarb equipped BMW Airhead, however until we are able to better address the fitment considerations and gain a better understanding of baseline settings like we have with the off-road 2-stroke market, we’re content to let it ride so to speak for now.
I have a 2001 kx250 with a BUD racing pipe and silencer so what carb would I need?
Hi Chet, for your KX250 we’d recommend the 38mm size SC2, available here: https://technologyelevated.com/product/38mm-sc2-smartcarb/ We just need to know how you ride the bike and what fuel type/oil ratio you’re mixing in order to pre-calibrate it specific to your needs.
Thanks for your reply. My applications are Honda NSR50 and NSR80 engines with the reed block entry at 43º forward of vertical. I am currently using an adapter block that reduces this by 13º, but normal carbs are not up to the job at that angle.
The resulting 30º angle forward toward the engine is workable with a SmartCarb, however proper float level becomes just a bit more important. The stock carbs are flange-mount correct? Ours are designed to be spigot-mount with a rubber flange and clamp.
Thank you. I only use spigot mount carbs so SmartCarb is a good option.
What setting should I start with i have a smart carb 38 ca kn air filter and open air box v force 3 reeds
What is the maximum degree of downdraft that is usable with a Smartcarb?
Hi Roger, the SmartCarb in its current, vertical mount configuration, performs best being tilted no more than about 35 degrees forward and up to 15 degrees either side. We have plans to eventually release downdraft versions. What is your application?
I currently run an H series on a modified 2009YZ125 and I love it. I am considering upgrading my 2018 KTM 150sx. What smart carb do you recommend??
Hi Troy, thanks for asking. If you’re happy with the Lectron on your ’09 YZ125 then you’ll be really impressed with the SmartCarb. We recommend the 36mm size SC2 for your 2018 KTM 150SX. It’s available here: https://technologyelevated.com/product/36mm-sc2-smartcarb/ The 150SX comes stock with a 38mm Mikuni TMX and typically we recommend replacing size for size but there are exceptions, including the 150 KTMs, where we recommend otherwise. The 36mm size SC2 will increase performance everywhere compared to the Mikuni, even on the top end. You can expect very crisp, clean, and strong throttle response down low with linear power delivery through the mid to top. The SC2 is a direct fit and accepts the stock throttle cable. Let us know if you have any questions about how to order, installation, or tuning.
Thank you for a very clear comparison.
How do you pitch your carb over a Lectron user that only had problems? How do you get that person to go from $550 spent on a turd. To an $800 different version? And I mean that not as an insult. But one metering rod carb to another. I’m in that boat.
We’re sorry to hear about your Lectron troubles. That’s a tough spot to be in and we can certainly understand your apprehension to try another metering rod style carburetor after having had that experience. While we can’t help you with the Lectron you have now, we can encourage you to work with Lectron to sort out any potential metering rod mismatch or workmanship issues. You may be able to sell it also, especially if it’s one of their later HV or H-Series models. We would also encourage you to check out our Facebook Page and Instagram account for customer feedback and testimonials. The Facebook Group SmartCarb Users is also a good resource for you when considering purchasing a SmartCarb. Lastly, as we hoped to clarify in this article, the SmartCarb is more than just a different version, but rather the careful development and culmination of a lifetime’s work on this fuel system concept.
What do you ride Dario?
I know some guys that have used lectrons with some success on big bore horizontal piston imported engines Like the Daytona 190s. These engines come with a Kehin 28 mm round slide carburetor. Is there a smart carb available that might work in this application? Most everyone spending money on these motors are going up and piston size and rod length ending up somewhere between 212 and 274 cc. If there is a carburetor you offer I would expect to likely have to weld up an intake to work, but without an airbox I’m not sure if the venting would function properly, or as described in this article. We race YCF mini Flat Track Bikes, and everyone I’ve ever seen has deleted the cheap airbox and opted for a pod filter.
Yes, although it is currently out of stock, we offer a 28mm SmartCarb that will fit the stock Daytona 190 and will also work well for the stroker big bores like Pirahna, Lifan, etc. The spigot diameters are nearly identical to the 28mm Mikuni VM roundslide. A flange may be necessary for your application and can be easily fabricated, or you can make an adapter flange for the engine and use a short rubber hose with clamps for attachment.
Running a pod filter, or even no filter is not a problem. The SC will read the air density and velocity at the front of the intake bell regardless of whether a filter or airbox is used.
We will have the 28mm size SC2 SmartCarb available again in the coming weeks so stay tuned!