Universal Throttle Cable Installation: A Comprehensive Guide

Achieving a clean and streamlined look for your motorcycle often involves addressing the visibility of wires and cables. This article provides a comprehensive guide to universal throttle cable installation, covering both internal throttle setups and external cable solutions for various carburetors and EFI systems. We will explore the steps involved in installing an internal throttle cable within custom handlebars, as well as the process of fitting a universal throttle cable to connect your gas pedal to your carburetor or EFI system.

Internal Throttle Cable Installation

This section details the process of installing a throttle cable inside your motorcycle's handlebars, creating a clean and minimalist aesthetic.

Preparing the Handlebars

Determine Handlebar Length: Begin by deciding the desired length of your handlebars. Use your grips as a reference to determine how much material needs to be removed. Understanding motorcycle handlebar dimensions chart is crucial before you begin. Gather all necessary components, including grips, controls, cables, and other essential parts.
Measure and Cut: Measure from the end of the left side of the handlebar to your marked cutting point. The right side requires more material removal to accommodate the internal throttle.
Account for Internal Throttle: Measure the length of the internal throttle mechanism (typically around 2-7/8 inches, but confirm with your specific unit) from the end of the right side of the bar. Mark this point. Then, position your internal throttle end at that mark and make another mark where the step ends and the slug begins.
Cut the Handlebars: Carefully cut the handlebars at your marked points.

Fitting the Internal Throttle

Prepare the Handlebar Interior: Most handlebars have an internal weld seam that needs to be removed for the throttle mechanism to fit correctly. Use a grinder to carefully remove the weld seam and any debris, ensuring a snug fit for the slug. Take your time and check frequently as you remove material.
Drill a Set Screw Hole: Measure the distance from the step on the throttle mechanism to the center of the set screw hole (e.g., 1 inch). Mark this measurement on the handlebar, center punch the mark, and drill a pilot hole. Then, drill the hole to the appropriate size for the set screw.
Clean and Test Fit: Clean the inside of the handlebar tubing with a barrel sander to remove any burrs created during drilling. Test fit the internal throttle to ensure a proper fit. Do not force the set screw.
Set Screw Placement: Determine the desired location for the set screw (e.g., at the bottom of the handlebar).

Routing the Throttle Cable Housing

Determine Cable Outlet Point: Decide where you want the throttle cable housing to exit the handlebars. This will depend on your handlebar style. For example, with Lowbrow Customs Rabbit Ears, the cable could run down the entire tube to the bottom of the tree. However, with T-bars, the cable might need to exit in the middle and run down the left side riser.
Measure and Cut the Housing: Determine the necessary length of the throttle cable housing. Ensure sufficient slack to prevent pulling on the cable when turning the handlebars and to avoid pinch points near the fork stops. Open the adjuster on the cable all the way as well.
Remove the Internal Throttle Cable: Once you're satisfied with the cable routing through the bars, pull the cable back off the bike and remove the internal throttle cable from the black cable housing.

Preparing the Throttle Cable

Measure for Cutting: Measure the distance from the slug of the internal throttle to the end without the small aluminum piece where the housing snaps into (e.g., 1-1/2 inches). Mark this measurement.
Mark the Cutting Point: From your previous mark, measure 1-1/2" closer to where the cable goes into the carb. Measure the step to the face of the slug on the internal throttle minus the little aluminum cap. Measure 1-1/2" from previous mark towards the brass ferrule and that will be where you need to cut.
Cut the Cable: Use a cut-off wheel to cut the cable, avoiding wire cutters, which can fray the cable.
Determine Inner Cable Length: Remove the slide from the internal throttle. Insert a small object, like an Allen wrench, into the cable opening to determine the correct length for the inner cable.
Measure the Slide: Measure the outside of the slide (e.g., 1/2 inch) to align with the end of the white plastic, providing a reference point for your next measurement.
Measure from the Bearing: Push the slide to the end of the throttle towards the slug and measure from the face of the bearing (e.g., 3/16 inch) to the end of the step of the slug.

Final Assembly

Reassemble the Cable: Feed the internal wire cable back into the black outer housing and run the entire cable back through the bike and bars.
Mark the Inner Cable: Measure 1-1/2" of the internal wire cable past the black cable housing end and make a mark onto the inside cable wire.
Finalize Measurements: Measure 1/2" from the face of where the cable goes in on the outside and it lines perfectly up with the plastic part of the slide. After determining the bearing to the end of where the cable would be is 3/16".

Final Installation

Install the Internal Throttle: Insert the outer housing cap of the internal throttle, then install the internal cable into the slide and lock it down.
Reassemble the Throttle: Put the slide into the thermal cable and reinstall your screw with bearings onto the slide.
Secure the Housing: Lock your outer housing and then insert the slug into the handlebars and line up your hole.
Tighten the Set Screw: Secure the slug in place by tightening the set screw.
Adjust the Cable: Adjust the cable at the adjuster near the carburetor to eliminate any slack.

Completion

Reinstall the air cleaner, grips, clutch lever, and brake lever (if applicable).

Universal Throttle Cable Installation for Carburetors and EFI Systems

This section outlines the process of installing a universal throttle cable for aftermarket carburetors and EFI systems, ensuring a proper connection between the gas pedal and the engine.

Understanding the Need for Universal Cables

Most factory throttle linkages are not compatible with universal aftermarket carburetors and EFI systems. This is where universal throttle cables and bracket kits become essential.

Lokar Performance Products

Lokar Performance Products offers U-Cut-to-Fit throttle cables and bracket kits designed to provide a clean and effective connection between the throttle lever and the gas pedal.

Components and Options

Cable Options: Lokar cables are available with stainless steel braided housing, black stainless steel braided housing, or black housing. All cables feature a specially extruded liner to extend the cable's lifespan.
Fittings: Aluminum fittings and ferrules are included to prevent fraying.
Bracket and Spring Kits: Cable kits can be paired with Lokar's bracket and return spring kits for a complete installation.

Installation Process

Gather Components: Assemble the necessary components, including the Lokar throttle cable, bracket, and return spring kit.
Bracket Installation: Install the Lokar bracket onto the carburetor or EFI throttle body. The Lokar bracket and return spring kit is specifically designed to fit the Holley Sniper EFI throttle body. There's even an adjustment screw to perfectly align the cable housing with the throttle lever.
Cable Routing: Route the throttle cable from the gas pedal to the throttle body, ensuring a smooth path without any sharp bends or obstructions.
Cable Length Adjustment: Measure and cut the throttle cable to the appropriate length. Lokar cables are designed to be cut to fit your specific application.
Cable Connection: Connect the throttle cable to the gas pedal and the throttle lever on the carburetor or EFI system.
Adjustment: Adjust the cable tension to ensure proper throttle response. The throttle pedal and throttle blades should move together. There should be no play in the pedal before the throttle opens and the throttle should be wide open when the pedal is at its maximum travel.
Final Checks: Verify that the throttle opens and closes smoothly and completely.

Step-by-Step Installation (Example: Lokar Cable on a 1968 Corvette with Holley Sniper EFI)

Adapt Pedal: Use a washer to adapt the Corvette throttle pedal to the Lokar cable ball end.
Mount Bracket: Mount the Lokar bracket to the Holley Sniper EFI throttle body.
Route Cable: Route the Lokar throttle cable from the gas pedal to the bracket.
Cut Cable: Cut the cable to the appropriate length.
Connect Cable: Connect the cable to the gas pedal and the throttle lever.
Adjust: Use the adjustment screw on the bracket to align the cable housing with the throttle lever.
Test: Verify smooth and complete throttle operation.

Universal Throttle Cable Kits

You can easily upgrade your stock throttle linkage to an aftermarket universal throttle cable kit (and kickdown for the auto trans) with Speedway Motors and Lokar. Lokar offers throttle cables for nearly every application you could need. The install featured here uses Lokar Hi-Tech stainless steel braided kits for both throttle and kickdown on Chevy 327 small block and TH350 in Corvette demo chassis.

Throttle Cable Function

A throttle cable serves as the link between your gas pedal and the throttle blade. As the driver presses or releases the gas pedal, the throttle cable controls the movement of the throttle plate, which then regulates the engine's speed. Unlike rigid mechanical linkages, a throttle cable provides flexibility in routing, allowing for easier adjustments. Changing pivot points or lever arms in hard linkages can alter the movement ratio, but this may result in unwanted driving characteristics, like inconsistent throttle response.

Troubleshooting

Problems with your throttle linkage can occur with factory or aftermarket components. The key is to ensure that they are correctly routed so that they can operate freely. A linkage or cable may come into close contact with the engine itself or the exhaust and then bind up when trying to re-route them.

Cable Considerations

Mechanical linkages should be free and clear of any objects through their entire movement. Cables donât have the same physical restraints, they can bend and flex around obstacles, making them the ideal link. Most cables use a plastic housing, even aftermarket braided cable housings have a nylon or plastic inner core for the cable to pass through. Heat is the biggest issue for a cable, as the inner lining can melt or deform, hindering throttle control. Even if the housing looks normal on the outside, the inside can swell from heat and bond to the cable. The other common issue for cables is sharp bends. While cables can certainly bend, there is a limit before the cable starts to get pinched in tight curves. Sweeping bends are always best, but sometimes they are unavoidable.

Installation Tips

Proper installation is key for achieving smooth, responsive acceleration and consistent performance. Installing and adjusting these cables is easy, you just need a little patience and planning. No special tools are needed, however a chop saw is recommended for cutting stainless steel cable housings, as the strands will fray and can cause difficulty upon reassembly.

Kickdown Cables

Kickdown cables control non-electronic automatic transmissions. When the throttle reaches WOT (Wide Open Throttle), the kickdown cable is pulled tight, which pulls a linkage or valve in the transmission, forcing it to downshift to a lower gear. This should only occur at WOT, so the adjustment of a kickdown cable is important when you have changed the carburetor or throttle body (check out the difference between throttle body vs carb. Stock cables do not have adjustable links, instead they use a long-slotted arm that allows the throttle to move freely until WOT. Donât confuse a kickdown cable for a TV (Throttle Valve) cable. Used on GM 2004R and 700R4 automatics, and Ford AOD transmissions, these cables require adjustment. If the TV cable is out of adjustment by even a tiny bit, the transmission may shift too fast and burn up the clutches.

Bracket Options

The first bracket is a Speedway Motors universal throttle cable bracket. This one is designed for factory-style cables which use square lugs to secure the cable. Aftermarket cables typically use threaded fittings, which will work in this type of bracket but are not ideal. Once the installation was completed, we swapped out the Speedway Motors bracket for the Lokar Hi-Tech cable bracket, which looks better as it was designed for the cables we used. We opted to show both brackets, as using the universal bracket is a common choice. The biggest benefit (outside of looks) to the Lokar bracket is the setscrew that stops the bracket from rotating on the single mounting bolt.

Kickdown Cable Necessity

You do not actually NEED a kickdown cable at all, your transmission just wonât downshift when you floor the gas pedal. You will have to select the lower gear yourself manually via the shift lever (shift from 3rd to 2nd for example). While that is certainly fun and all, it gets old fast.

Detailed Installation Steps with Speedway Motors and Lokar Brackets

Pedal Positioning: Weâre using a Speedway Motors pedal, in the stock location, the cable must have a clear path through the firewall from the pedal.
Firewall Installation: Next, we installed the throttle cable housing into the firewall and threaded on the nut.
Bracket Mounting: Under the hood, the new Speedway Motors bracket was mounted to the carburetor left-rear stud. The bracket has adjustable cable positioning. The cable housing was routed through the bracket. We played with different routings, as the hole in the firewall is directly behind the cylinder head, leaving a tight space.
Housing Preparation: We slid the ferrule past the cut line on the housing so that when it is cut, the ferrule can be pushed up to the frayed edges for a clean, poke-free installation.
Cutting the Housing: Stainless steel housings are best cut with a chop saw, but you can use a cut-off wheel or hacksaw. Lokarâs non-stainless housings can be cut with side-cutters.
Reinstall Housing: We reinstalled the housing to the firewall and inserted the cable. The other end of the housing was secured to the bracket. This is a round tube in a square hole, it is a little sloppy, but once the nut is tightened, it works fine.
Throttle Fitting Installation: We installed the throttle fitting to the carb and then slid the cable ferrule onto the cable. Using the supplied Allen wrench, the set screw was tightened to secure the cable in position.
Cable Assembly: The cable assembly was connected by threading the two pieces together.
WOT Adjustment: With the pedal on the floor the throttle should be wide open. There should be no additional movement. If the throttle is not at WOT when the pedal is on the floor, thread the cable end fittings together until it does.
Kickdown Cable Location: Moving under the vehicle, we located the kickdown cable on the transmission. This is usually on the passenger side, but not always. Chrysler transmissions have this on the driverâs side. We removed the cable and disconnected the lever from the cable. On GM transmissions, this is a little S-bend, just work it around the bends.
Lokar Housing Installation: Next, we installed the new Lokar housing with the cable removed and no O-ring. Under the hood, we routed the housing to the bracket. Lokar supplies a polished clamp and bolt, which we slipped onto the housing. The housing is sealed to the case with a supplied O-ring.
Throttle Bracket Pin: Back under the hood, the supplied throttle bracket pin was installed on the throttle arm. This should be on the lower half of the arm.
Kickdown Adjustment: Adjusting the kickdown requires pushing the gas pedal to the floor for WOT. Pull the cable tight and tighten the cable stop. Verify the pedal opens the throttle to WOT without resistance and returns home.
Lokar Bracket Set Screw: Lokar makes this cable bracket for their cables. It works for both throttle only and throttle and kickdown or TV cables. We loved this feature on the Lokar bracket. The set screw is adjusted to keep the bracket from rotating on the carb stud.

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