How to Install the Throttle and Choke for Honda GX and GXV 600 Series Engines with Video

The throttle and choke are critical points of failure for Honda lawnmower engines, especially after weeks or months of disuse. They control the air pressure by limiting the ratio of fuel and air brought into the cylinder to get the engine going. With too much or too little air in the carburetor, the engine may not start. This is a tell-tale sign of a choke that needs to be replaced.

Owners of GX and GXV 600 Series engines may have horizontal or vertical shaft connections. This article provides step-by-step installation tips for the throttle and choke on a horizontal shaft engine, but vertical shaft repairs can use the same steps in a slightly different configuration. Your engine replacement kit will come with clear instructions on how to use the included parts to install the throttle and choke on your mower’s engine. The chokes are specific to these Honda engines, but throttle installation will be similar for other small lawnmower repairs.

This guide aims to expand the instructions included in engine replacement kits to help you successfully install these parts and get your old mower running like new.

1.   Trim and Route Cables

The engine repair kit will include the needed cables, including replacement throttle or choke cables. The cables will come in a stock length, which allows them to be trimmed to any specification needed. Owners should block out the internal cable routing before trimming or installing the cable to make sure the final length matches the needs of the engine.

In Honda engines, these cables can be routed to one side or one can be routed on each side. This allows for some freedom when routing these cables depending on the length they’ve been trimmed and the specific configuration you’re working with. When measuring the mock cable configuration, it’s important to use wide sweeping turns to allow free movement of the cable within its sheath.

If the measurements are taken too tightly, the cable will bend at hard, restricted angles, resulting in internal friction that can cause system failures. The goal is for the cable and wiring to connect comfortably without unnecessary tension or binds. If this is mishandled, your lawnmower repair could run into problems.

2.   Verify Throttle Linkage and Governor Configuration

Throttle actuation at the carburetor can only occur when crankcase pressure has built up from the engine operating. The linkage between the governor arm and carburetor should not move as the throttle lever actuates with the engine off. This is important to consider when mocking the routing path of the cable. Make sure you measure a sufficient length when adjusting the slack on the cable for operating and non-operating positions. 

Think of it this way. When the engine is off and you move the throttle lever, the throttle cable expands or contracts in relation to the carburetor linkage, throttle plate, and governor arm. Since the engine is off, the governor system isn’t actively controlling the throttle linkage. It’s stationary, meaning the movement of the arm is determined entirely by spring tension and cable pull.

For cable installation, this means that whatever length of cable you use should be one where the governor arm and carburetor throttle plate can move freely. In the high-speed position, the throttle plate should fully open. In the idle position, it should fully close.

A cable that is too long may prevent the throttle from opening and closing fully. Cables that are too long will reduce the control precision you will have on your finished engine. Cables that are too short may have erratic and uncontrollable engine speeds due to the throttle never fully reaching the idle position.

3.   Install Cables

In this example, solid throttle cables and choke cables are routed on the starter side of the engine. However, Honda GX engines can be configured on either side.

The z-bends are connected through the holes on the outside of the choke lever. The clamp should be loosened to give the cable room to be inserted into the clamp and secured. Note that the clamp should not be overtightened, which would result in restricted movement and increased friction within the cable. This process is similar for throttle cable installation, except for the position of the z-bends. They should be inserted through the top holes in the lever to allow the cable to pull and actuate the throttle.

This installation is similar if performed on the oil filter side of the engine, but since the cables are coming in from opposite sides, the position of the clamps is reversed. From the oil filter side, the choke cable needs to pull to close the choke. This makes it necessary to use the inside attachment holes. For the throttle cable on the oil filter side, the z-bends should be attached to the bottom holes of the lever to ensure proper actuation. Once again, refrain from fully tightening the clamp since the cable will need to be adjusted once the engine is operating.

Some applications may require a flexible braided throttle cable, which must be attached to the specific Honda wire holder that guides it to the carburetor linkage. This helps maintain consistent throttle operation without the cable binding.

In this case, the holder may need to be relocated from its factory position before the cables can be attached. A flexible cable is ideal for throttle setups that are long, curved, or high-movement. With the proper adjustment, the Honda wire holder will secure the cable casing to allow free movement of the inner wire and prevent friction.

4.   Test Operations

These configurations may need to be tested and fine-tuned. Observe the full range of operating motion by moving the throttle lever. Make sure the throttle plate can fully open and close with minimum resistance. Finally, start the engine to verify the smooth operation of both the throttle and choke cables at idle, part throttle, and full throttle positions.

If the cable is too long, trim the outer casing first before cutting the braided inner wire. Make sure it’s slightly longer than the casing to enable a wider range of motion with less slack. Remember that a wire can always be cut shorter but can never be cut longer. Adjust until the cable is a suitable length at all throttle positions.

Repower Specialists Provides Comprehensive Engine Repair Kits

These tips aim to help Honda engine owners with their throttle and choke cable installations for GX and GXV 600 series engines. However, any small mower engine will follow similar procedures. Our conversion kits for John Deere F680 Honda GX630 engines will offer very similar repairs.

With an engine replacement kit from Repower Specialists, you will get the tools and instructions you need to successfully pull off this repair. Instead of spending a premium buying a new mower, our Repower kits will allow you to save money while increasing the control precision and efficiency of your old mower’s engine.

Contact us to learn about our engine conversion kits and make your lawnmower repair more successful.

For a visual demo of the above instructions, visit this tutorial video we made on throttle and choke installation procedures for Honda GX Series mower engines:

If you have any further questions, we are here to support you as part of Repower's Unlimited Technical Support for all Commercial Grade engine replacement kits purchased. 

Please contact a technician through our Technical Support Form.