1974: The Foundation — A Drag Racing Carburetor
Lectron Fuel Systems was founded in 1974 by Norman Quantz, a WWII pilot and engineer. Quantz observed the vortices formed on the trailing edge of aircraft wings and recognized that the same pressure differential principle could be applied to fuel metering. This insight led to the invention of the Lectron metering rod—a tapered, flat-faced rod that creates a localized low-pressure wake inside the carburetor bore, drawing fuel proportionally to engine demand.
The original Lectron was designed exclusively for motorcycle drag racing. In drag applications, throttle input is essentially binary: closed at the line, wide open down the track. There is no need for nuanced transitional fuel delivery between throttle positions. The metering rod handled this perfectly—a single, continuous fuel circuit that replaced the pilot jet, needle, and main jet found in conventional carburetors.
The design was an immediate success. Lectron became OEM on Penton motorcycles, was offered as a factory option on Harleys, and quickly became the dominant carburetor in motorcycle drag racing, flat track, and road racing applications.
The 1980s: Off-Road Discovery and the Limits of a Single Circuit
Lectron’s focus remained on drag racing throughout the late 1970s and into the 1980s. However, riders outside the drag world began installing Lectrons on off-road motorcycles and motocross bikes on their own. These riders were drawn to the simplicity—no jetting, automatic altitude compensation—but their riding exposed a fundamental limitation.
In off-road and motocross riding, throttle input is constant and varied. Riders use every position from idle through quarter, half, three-quarter, and wide-open throttle, often transitioning rapidly between them. The single metering rod circuit delivers fuel on a linear curve tied to throttle position. This means any change to fuel delivery at one throttle position affects the entire range. Enriching the bottom end to improve low-RPM response also enriched the midrange and top end. There was no way to optimize one region of the throttle range without compromising another.
This is the inherent limitation of any carburetor that relies on a single metering circuit: linear fuel delivery cannot match the non-linear fuel demands of an engine operating across a wide throttle range. Lectron recognized this limitation from direct field feedback—and began engineering past it.
Any fuel system still relying solely on a single metering rod circuit is operating within this same constraint—a design chapter Lectron closed decades ago.
Mid-1980s: The Power Jet — Independent Top-End Fuel Control
The first major evolution of the Lectron platform was the Power Jet, developed in the mid-1980s. Originally designed to give drag racers trackside adjustability—the ability to add or remove fuel between runs to keep motors optimal—the Power Jet introduced an entirely new fuel circuit independent of the metering rod.
The Power Jet draws fuel from a dedicated nozzle positioned in the center of the airstream. It activates at higher throttle positions (approximately half throttle and above) based on venturi velocity, providing enrichment that is dependent on airflow mass rather than throttle position alone. Critically, it is controlled by an externally adjustable tapered screw—no disassembly, no jet swaps. Racers could fine-tune top-end fueling on the fly.
For the off-road application, this was the first step toward solving the single-circuit compromise. Riders could now adjust high-RPM fuel delivery independently of the metering rod’s primary curve, allowing the rod to be optimized for idle and low-speed response without over-fueling the top end.
The Lectron platform now operated on two fuel circuits: the metering rod for continuous vacuum-referenced fuel delivery, and the Power Jet for velocity-activated top-end enrichment.
2014–2019: The Off-Road Pivot — High-Velocity Bore Design
For nearly three decades after the Power Jet, Lectron’s platform continued to dominate drag racing while maintaining a presence in off-road through the standard 36mm and 38mm carburetors. The 36mm favored low-end power; the 38mm favored top-end flow. Both used 2mm of bore taper.
In 2014, Lectron made an intentional decision to engineer the product specifically for off-road performance. The first modifications targeted the known weakness: bottom-end throttle response in varied riding conditions.
Drawing on aerodynamic principles from drag racing—specifically the velocity stack concepts used in Formula 1 and Top Fuel applications—Lectron’s engineering team developed a high-velocity bore design. Rather than changing the bore’s cross-sectional shape (which would compromise flow), a tapered sleeve was introduced that increased airflow velocity at the metering rod pickup point, strengthening fuel signal without sacrificing peak airflow capacity.
Additional improvements included high-velocity insert ramps to increase air velocity in the low throttle range, and fuel encapsulators at the metering rod pickup system that held fuel in place during high-vibration conditions—a critical issue in off-road riding that never surfaced in drag racing.
38HV (Late 2016)
The 38HV formalized the high-velocity concept. This 38mm carburetor used a bore sleeve to create approximately 1.5mm of additional taper. On two-stroke dirt bikes, this left peak horsepower unaffected while meaningfully boosting bottom-end power and throttle response.
H-Series (Mid-2019)
The H-Series eliminated the sleeve entirely by molding the taper directly into the carburetor body at 4mm of taper. This improved both peak horsepower (over the 38HV) and low-end feel (over the original 36mm). The H-Series also introduced a more aggressive slide cutaway and served as the platform for Gen II four-stroke and Harley-Davidson models.
However, the H-Series body was still relatively long and tall compared to modern OEM carburetors, and fitment still required aftermarket throttles, cables, and additional components. These were the problems the next generation would solve.
2022: The Billetron — Complete Platform Redesign
The Billetron 38, released in 2022, was not an incremental improvement—it was a ground-up redesign informed by years of off-road customer feedback.
Material and Construction
The Billetron moved the entire carburetor body to billet aluminum, replacing the cast construction used since 1974. Billet machining enabled tighter tolerances, with many critical dimensions held to less than three ten-thousandths of an inch. This precision directly improved fuel metering consistency and product-to-product repeatability.
Fitment and Form Factor
The body length was reduced to 78mm—matching the form factor of modern short-body Keihin and Mikuni carburetors. The redesigned top cover accepted most OEM two-stroke cables
directly, eliminating the need for aftermarket throttles, cams, and adapters. The choke was relocated to the left side for easier access.
Bore and Airflow
The Billetron introduced a tailored high-velocity bore design optimized for specific displacement ranges. Combined with a new H-Style slide that improved throttle feel and fuel signal
at low RPM, the Billetron delivered a significant improvement in torque production and throttle response over the H-Series.
Precision Fuel Delivery
The metering rod adjustment was refined to 1/8th-turn increments, translating to 0.003” of adjustment per step. A redesigned all-billet pickup tube with o-ring sealing improved fuel metering precision and was made user-serviceable. The entire carburetor was designed to be DIY rebuildable—a first for the Lectron product line.
2023–2024: The PRO-Series — Multi-Circuit Fuel Delivery
The Billetron’s improvements in airflow velocity and low-end response revealed a new engineering challenge. The redesigned bore was now capable of delivering significantly more air at low
throttle positions than previous generations—but fuel delivery from the metering rod and Power Jet alone could not fully match this improved airflow curve.
The core issue: airflow delivery to the engine is not linear across throttle positions. At 1/4 throttle, total air delivery might represent 35% of maximum. But at 1/2 throttle, total air delivery is significantly less than double that figure, because engine vacuum and velocity behave differently at each throttle position. The fuel system needed to match this non-linear airflow behavior—not just respond to throttle position.
The Torque Jet
The PRO-Series introduced the Torque Jet: a tunable bypass fuel circuit that activates between approximately 5–20% slide opening. Positioned to deliver fuel precisely where the engine’s
increased velocity and airflow demand it most, the Torque Jet provides immediate off-idle enrichment that the metering rod alone cannot supply at low vacuum levels.
The Torque Jet is externally adjustable—a quarter-turn can shift engine character from smooth tractability to aggressive response. This gave riders independent control over low-throttle fuel delivery for the first time in Lectron’s history.
Additional PRO-Series Engineering
Beyond the Torque Jet, the PRO-Series platform included several critical engineering changes: internally routed fuel circuits for both the Power Jet and Torque Jet, reducing fuel delivery delay; a redesigned needle and seat for improved sealing under vibration;
an H-Style slide with an Air Redirect ramp that redirected airflow for stronger fuel signal; and availability of a TPS (Throttle Position Sensor) option for data acquisition.
Three Independent Fuel Circuits
With the PRO-Series, Lectron now operates three coordinated but
independent fuel systems: the metering rod for continuous vacuum-referenced fuel delivery from idle through full throttle; the Torque Jet for adjustable off-idle and transition enrichment; and the Power Jet for velocity-activated high-load enrichment. Each circuit responds to a different aerodynamic signal within the venturi, creating a continuous, self-adjusting fuel curve across the entire throttle range.
Late 2024: The Xcelerator Metering Rod — Transient Fuel Delivery
Even with three fuel circuits optimized across the throttle range, one universal carburetor problem remained: the momentary fuel delay during rapid throttle opening.
When a rider opens the throttle quickly at low RPM—what riders call “whacking the throttle”—there is a brief rise in pressure inside the carburetor that prevents immediate fuel delivery. The engine demands fuel instantly, but the carburetor is momentarily playing
catch-up. At best, this creates a slight lag. At worst, it produces the hesitation or bog that has plagued carburetors since their invention.
Lectron’s solution was the Xcelerator Metering Rod: a patented redesign of the metering rod itself that integrates a mechanical accelerator fuel delivery system directly into the rod.
The Xcelerator rod includes an internal fuel reservoir, a top-side orifice, and a controlled lower discharge slot. At idle and steady throttle, fuel fills and stages in the reservoir, held near the venturi. During rapid throttle opening, the stored fuel is released immediately—before engine vacuum has time to recover—providing a burst of enrichment exactly when the engine needs it most.
As RPM builds and vacuum stabilizes, the system transitions seamlessly back to standard metering rod operation. The reservoir refills and stages for the next throttle event.
The Xcelerator rod achieves this with no pumps, no o-rings, no electronics, and no additional moving parts. It is a purely mechanical system that delivers fuel as fast as the rider can
open the throttle. The result is throttle response that riders describe as comparable to electronic fuel injection—from a fully mechanical system.
2025–2026: The EVO H-Series — Modernizing the Legacy Platform
While the PRO-Series represents the peak of Lectron’s performance engineering, not every rider needs or wants
three fuel circuits and maximum adjustability. Many riders value the simplicity of Lectron’s original set-it-and-forget-it design philosophy.
The EVO H-Series, released beginning in October 2025 with remaining sizes following in 2026, brings the Legacy carburetor model up to current manufacturing and design standards. The
EVO incorporates key Billetron-era improvements: billet aluminum construction, a shorter body, a hard-anodized slide, choke relocation to the correct side for easy access, and a DIY-rebuildable design.
The EVO does not add the Torque Jet or Power Jet circuits found in the PRO-Series. It is built around the proven metering rod and Power Jet combination, refined with modern materials and precision manufacturing. For riders who want consistent, adaptive performance without managing multiple fuel circuits, the EVO delivers the Lectron experience in a modern, reliable package.
1974 → Original Lectron → Metering Rod replaces pilot, needle and main jets → Simplifies fuel delivery for drag racing → 1 (Rod)
Mid-1980's → Power Jet Addition → Externally adjustable velocity-activated enrichment → Independent top-end fuel control → 2 (Rod + PJ)
2014-2016 → HV/38HV → High-velocity bore sleeve for increased low-end signal → Bottom-end reponse in off-road use → 2 (Rod +PJ)
2019 → H-Series → Molded taper bore, aggressive slide cutaway → Improved peak HP and low-end feel → 2 (Rod+PJ)
2022 → Billetron 38 → Billet construction, 78mm body, tailored bore → Fitment, precision, torque delivery → 2 (Rod+PJ)
2023-2024 → PRO-Series → Torque Jet, Air Redirect ramp, internal routing → Non-linear fuel mathcing across throttle range → 3 (Rod+TJ+PJ)
Late 2024 → Xcelerator Rod → Mechanical transient fuel reservoir in rod → Bog / hesitation on rapid throttle opening → 3 + transient
2025-2026 → EVO H-Series → Billet Legacy with modern construction → Modernized simplicity for set-and-forget riders → 2 (Rod+PJ)
Why This Matters: The Limitation of Single-Circuit Designs
The metering rod remains the core of every Lectron carburetor. Its ability to meter fuel based on engine vacuum signal—rather than fixed jet calibration—is what gives Lectron carburetors their automatic altitude and temperature compensation.
But the metering rod alone, operating as a single fuel circuit, has an inherent constraint: its fuel delivery is tied linearly to throttle position. This was sufficient for drag racing, where throttle input is binary. In off-road riding, where throttle positions are constantly varied and transitions are rapid, a single circuit cannot independently optimize fuel delivery across the bottom, middle, and top of the throttle range.
Lectron learned this from its own product history. The original platform—a single metering rod with no supplementary circuits—worked brilliantly in its intended application. But when riders demanded more, Lectron engineered more: the Power Jet, the high-velocity bore, the Torque Jet, the Xcelerator rod. Each generation solved a specific limitation that the previous design could not address.
A fuel system that still relies on a single metering circuit—regardless of bore shape or rod geometry—is operating within the same fundamental constraint that Lectron identified and moved past across multiple generations of development. The question is not whether a metering rod carburetor works. It does. The question is whether a single circuit can deliver the fuel precision that modern off-road engines demand across the full throttle range.
Lectron’s answer, built across five decades of continuous engineering, is that it cannot—and that is exactly why the platform kept evolving.
