Lectron has been designing and manufacturing simple, high performance fuel systems in the United States since 1974. With a rich history in practically all divisions of two-wheeled motorsports, we are proud to have you as a part of our legacy.

 Lectrons outflow comparably sized carburetors while delivering fuel in a more finely atomized form. This creates better throttle response and more horsepower, all while staying in tune throughout a wide range of elevations and temperatures. Instead of rejetting throughout the day, you get to spend more time riding.

Each metering rod has a specific grind profile that has been pre-selected for your application. 

Tuning Spark Notes: 

Please read detailed tuning instructions later in this manual

1. Tune your rod first. If you have to turn your idle screw more than 0.5 turns either way, adjust your idle using your rod! Only tune the rod for idle and always reset your idle screw back to the starting setting when adjusting the rod.

2. Tune your Torque Jet second (bottom screw). This controls fueling from just off idle through half throttle. Tune this circuit for best response in that range.

3. Tune your Power Jet last (top screw). This controls fueling from half throttle to full throttle. Tune this circuit for best response in that range, and best peak power. 

Disclaimer: Lectron products come preset with a base tune determined by in-house testing, rider feedback, and other research. Each application can be influenced by external factors resulting in necessary tuning. Examples of these factors are: riding style, local fuel, custom engine work, etc.

Lectrons are mechanical fuel systems that use physics to compensate for a wide range of elevations and temperatures as well as humidity and other factors that effect air density. They DO NOT mechanically change their own tune and cannot sense load. 

For extreme environment applications like dune riding, snowbiking, ice racing, Supermoto, or other related activities under variable loads, you may need to make tuning changes.  

These are general steps and guidelines for installing your new Lectron carburetor. The actual steps you take may vary. 

Step 1: Prepare the Bike

• Turn your fuel off and disconnect the fuel line from the carburetor. 
• Drain the bowl if there is fuel in it. 
• Remove the seat and fuel tank. 
• Loosen up the center subframe bolt(s) and remove the lower subframe bolts. 
• Loosen the hose clamp on the air box side of the carburetor.

Step 2: Uninstall the Carburetor

• With the subframe rotated upwards, loosen the hose clamp on the engine side of the carburetor and remove it from the frame.
• If your carburetor has electrical plugs attached to it, disconnect them. If your Billetron Pro is not TPS equipped, tape or heat shrink the ends up to keep dirt out, and zip tie the plugs out of the way (usually to the frame up under the gas tank). 
• Disconnect the factory throttle cable from the slide. You will need to collapse the spring against the top cover in one hand, and push the throttle cable in, then outwards and it will come free. 
• Thread the top cover off of the factory throttle cable.  On some models, you may also need to remove the lock nut as well to achieve proper freeplay. 

Step 3: Install the Top Cover, Gasket, Spring, and Slide

• Thread the Billetron top cover all the way onto the factory throttle cable. Do not completely tighten this as you will need to orient the front of the top cover to face the front of the bike. 
• Install the Billetron top cover gasket and spring onto the cable.
• Collapse the spring up against the top cover so the cable is free, then insert the ball end of the cable into the opening on the face of the slide. Release the spring into the hole on the slide as pictured. 

Step 4: Install the Billetron

• Seat the spigot of the Billetron into the intake flange, leaving the hose clamps loose. If the carburetor does not fully seat, you may need to trim the locating tabs off of the flange.
• Route the vent lines down by the shock. If you choose, you can route one or two vent lines up towards the frame or into the airbox. 
• Do not restrict the vent lines with wire or zip ties, or route them into an unvented catch can.
• Confirm that the slide is open no more than 1/8” in the bore of the carburetor. If it does not close enough, thread your cable adjusters together first. 
• If you still do not have enough free play, remove the lock nuts from the carburetor side first, and the throttle side if necessary. 
• If you have our TPS-equipped Billetron Pro, it may be easier to temporarily remove the TPS sensor from the carb  to remove the slide, depending on your model of bike. If you remove the sensor, once the slide is reinstalled, plug in the plug on the bike’s wiring harness to the plug on the sensor, and mount the sensor on the carb body with the marks aligning (if present). If you have any remaining wires, tape or heat shrink them to keep out dirt, and route them out of the way. (please see the above video

Note: Starting the bike on a metal stand on a concrete floor can cause excessive vibration and make the carburetor overflow.

First Start

• Turn on the petcock and watch the float bowl fill with fuel. There should be a small air pocket in the top right corner of the float bowl.
• Pull the choke and fire the bike up. 
• You may need to blip the throttle to keep the bike running as these chokes are very rich. 
• Run the bike for a few seconds on the choke, then turn it off. 
• Continue lightly revving the bike until it is up to operating temperature. 
• If the bike is making an unusual noises, pinging, revving uncontrollably, or anything that may indicate an issue, turn it off immediately.
• Once the bike is up to operating temperature, take it for a nice, easy test ride. Listen for any indications that it could be running too lean or too rich and adjust as necessary. If you are unsure which way to go, always start going richer first. 

IF THE BIKE WILL NOT START

• Pull the spark plug and see if it is wet or dry.
• If it is dry: Take 3 vent lines in one hand and cover them with your thumb. Lightly blow in the 4th one and it will force fuel up the power jet line and into the bore of the carburetor. Continue trying to start the bike. If this is the only way your bike will start,  check for spark and proper compression. A leak down test is an easy way to confirm that the bike is generating proper vacuum to the carburetor and there are no air leaks.  This method for starting is NOT meant to be a permanent solution. 
• If it is wet with fuel: Install a fresh spark plug and continue trying to start it. If it will not start after a few cycles, hold the throttle wide open and try to start it. If it still will not start and the plug is wet again, refill the tank with fresh gas, confirm the air filter is clean, and try again. Further troubleshooting steps include checking the stator and coil for proper output. 

Setting Cable Free-play

• See video above
• Once the bike is up to operating temperature, make sure the bike is not loaded up and set the idle to 1300-1800 RPM. 
• Back the cable adjusters out JUST until you hear the idle RPM begin to increase. 
• Thread the adjusters back in 3-5 turns and lock them there. 
• Confirm that you have enough free-play to adjust the idle by turning the idle screw out and lock the adjuster in place. If turning the idle screw out does not affect the idle RPM, then turn the cable adjusters in further to add more free-play.
• If your cable adjuster at the throttle has too many threads showing or will not achieve the proper amount of free-play, use the other adjusters on the cable or at the top of the carburetor to do so. 

Note: Always turn the petcock off after riding to prevent the possibility of flooding the engine.

Lectron Basics 

Lectrons use the density of the air, the vacuum from the engine, and the grind of the metering rod to deliver the proper amount of air and fuel in a wide range of elevations and weather conditions. 

Lectrons come pre-tuned based on years of testing and feedback. Some tuning may be required due to modifications, different fuels, and personal preference. All carburetors are given a basic starting point to tune from. This is based on being gauged with our Fuel Ratio Tool and measured with calipers. Starting points can vary due to the batch the rod comes out of while still delivering the exact same fuel profile. DO NOT USE A MEASUREMENT FROM ANOTHER CARBURETOR.

Our new Billetron Pro model has the additional adjustability of two power jets, one for high throttle openings (power jet), and one for low throttle openings (torque jet).  Our patented metering rod still serves as the basis for fuel delivery and self compensates for atmospheric conditions, while the two power jets serve to supplement fuel delivery while providing independent adjustment for fuel delivery across all throttle ranges, as well as greater external adjustability so you spend more time riding and less time tuning than ever before. Some metering rod adjustments may still be required depending on mods and conditions, however these have now been minimized in the Pro model. 

Lectrons do NOT compensate for engine load. If you plan to use your Lectron for snow biking or dune riding, continue to read for instructions on how to tune specifically for those high load applications.

Note on Choke: Our carbs have a very aggressive choke, and the bike will not run for a sustained period with it on. The choke should only be used on cold starts and should be turned off immediately after the engine starts. DO NOT tune around the bike being overly rich with the choke on, or your engine will be too lean during normal operation.

Tuning Methodology

Due to the proprietary nature of our carbs, the tuning methodology differs somewhat from traditional carburetors. The following steps should be taken in order to achieve the desired carb settings. Do NOT tune it before riding it unless there is an obvious rich or lean condition. 

1. Set idle: The bike must be up to operating temperature before setting the idle. Lectron Carbs respond best when the slide is set at 2mm or 0.078” from fully closed and are set to this distance from the factory. This slide position corresponds to a fairly high idle (1600-1900 RPM on most bikes), which is completely normal. The air-fuel ratio (AFR) with the throttle closed determines the idle RPM. The leaner the AFR, the higher the bike idles. If more than 1 turn in or out of the idle screw is needed to raise or lower the idle, go back to the standard setting and adjust the metering rod. Adjusting the metering rod clockwise will richen it (right, richer), which will lower the idle. Adjusting the metering rod counterclockwise (left, leaner) will raise the idle. Fine tuning the idle can then be performed again with the idle screw. Note: if having difficulty setting the idle, confirm the starting slide position. This can be done by using a 5/64” drill bit as a gauge. Insert the drill between the slide and the bottom of the carb bore and adjust the idle screw until the slide barely touches it. If that does not help, you may have an air leak, worn reeds, or may need a different metering rod for your application 

Tip: the correct idle gap is generally between 4-4.5 turns from all the way in on the idle screw on the 38, and 5-5.5 turns on the Big Air. Always reset your idle screw back to your starting setting when making metering rod adjustments.

Metering rod adjustment: See the Quick Tuning Guide near the end of this manual

2. Setting the Torque Jet: On most bikes, the starting position for this knob is 3/4 turn from all the way in (LIGHTLY SEATED). This adjustment will fine tune your fuel delivery at lower throttle openings and controls your throttle response starting at about 1/8 throttle. To diagnose whether the bike is lean or rich on the torque jet,  ride the bike and get it up to operating temperature. Then, install a brand-new spark plug and ride the bike at below half throttle for about 30 minutes. Roll the throttle between 1/4 and 1/2 throttle at different speeds in 2nd and 3rd gear to load the motor differently. The bike should pick up cleanly. If it sputters or loads up from riding at constant throttle, you are rich. When accelerating, rich symptoms include: the bike intermittently cutting in and out, smoking excessively, exhaust note may sound “wet” or feel like the choke is on. The solution is to turn in (leaner) the torque jet screw 1/8th turn and repeat. If the bike bogs and the bog gets worse the faster you open the throttle, it is too lean. Other lean symptoms include: If the bike feels like it revs up quickly in neutral but lacks torque under load, runs hot, detonates, or sounds hollow and raspy. The solution is to go to 1/8 turn out (richer) and repeat. If you are not able to get rid of a lean condition with the torque jet, try richening the metering rod a quarter turn. If you have to richen more than 1/2 turn from the rod setting that gives the best idle, you may need a different metering rod.  

Tip: Generally too lean will not like the throttle being opened quickly and too rich will not like the throttle opened slowly or held constant. 

Note: As with the rod setting, there is some degree of rider preference. Being slightly rich will run well under high load, but not like constant throttle (motocross, sand, etc). Slightly lean will run well at constant throttle, but not high load (flowy woods, play riding, beginners). Ensure your bike is not running hot, detonating, or fouling plugs. If you are having to turn the torque jet in or out more than 1/2 turn in either direction for the desired effect, your metering rod setting or metering rod type may need to be changed. Also note that torque jet settings of more than 1.25 can cause richness on deceleration and will start to effect top end performance. 

3. Setting the Power Jet: On most bikes, starting position for this knob is 3/4 turn from all the way in (LIGHTLY SEATED). The Power Jet is the fine-tuning device for half to wide open throttle. Always adjust the Power Jet richer first unless you are certain the bike is already too rich. If you richen the Power Jet by 1/2 turn and it stays the same or gets worse, try going leaner 1/8 to 1/4 turn at a time. If the overrev drops off too early, the Power Jet is usually too rich. You can open the Power Jet another 1/4 turn to confirm this before going leaner. If the power has dips or is erratic at high RPM, the Power Jet is usually too lean. If you have gone leaner and richer on the Power Jet and the peak HP and overrev does not improve, adjust the metering rod (usually richer). If you richen the metering rod and the peak HP and overrev improves but the bike no longer idles or responds well, go to the next richer series metering rod. Look for the same symptoms listed for the torque jet to avoid overly rich or lean conditions.

Note: Sustained wide open riding (Pro MX, sand/dunes, snow bike, etc) requires more fuel to keep the engine temperatures in a safe range. We recommend setting the power jet 1/4 to 1/2 turns richer than normal for these types of riding. Never ride with the power jet all the way closed. If the bike runs ideally with the power jet fully closed, start by going 1/8 to 1/4 turn leaner on the torque jet, but you may need a different metering rod or your there is an underlying troubleshooting issue.

Verify: Pull the spark plug after about 2 hours of run time and examine the color. Two strokes make the best power with a dark brown or light black spark plug. A leaner setting will make the throttle response crisper. A richer setting will create more torque. If the plug is white and speckled, richen torque jet and the metering rod. If the plug is black or wet, lean out the power jet and metering rod. See the “Two Stroke Metering Rod Tuning” section for more information.