Adjustment of Motorcycle Throttle Free Play

Adjustment of Motorcycle Throttle Free Play

I will write about the adjustment of the throttle cable on my CBX1000.
Please note that the method I use might deviate from standard procedures or contain errors, so I appreciate your understanding.
This adjustment is for the FCR carburetor.
First, I'll outline the process, then go into the details.

Throttle free play is generally said to be about 5mm.
If the throttle does not return smoothly when turning the handlebars left or right, there might be an issue with cable routing.
A proper throttle cable should ensure that the throttle returns smoothly even when the handlebars are turned fully in both directions.
After adjusting the throttle cable, always check if the throttle returns correctly when turning the handlebars left and right.

When replacing the throttle cable, first attach it to the throttle holder, then to the carburetor side.
Check that the float valve opens fully when the throttle is fully opened.
If the float valve doesn’t open completely, you can adjust it using the tension of the pull-side throttle cable on the carburetor side.

To reduce throttle free play, move the pull-side adjuster (long nut) towards the carburetor.
If you move the return-side adjuster towards the throttle, the tension will increase.

Throttle free play should only be adjusted using the pull-side adjuster on the throttle side.
If the throttle tension decreases, adjust the return-side to tighten it up.

That’s the process in writing.
In the next section, I’ll explain with photos.
For those of you doing DIY work, I hope this can be helpful.
Reading this through to the end before starting the work will help improve your understanding.

So, let's get started!

How to Adjust Throttle Free Play

By moving the adjuster [blue ①] towards the carburetor, you can reduce the throttle free play.
If the throttle return tension feels weak after adjustment, move [blue ②] towards the throttle holder to increase the tension and ensure a stronger throttle return.

Before adjusting the throttle free play, there is something you must check.
Always make sure the throttle returns correctly when you turn the handlebars left and right.

Sometimes, you may experience an issue where the throttle doesn't return properly.
In that case, review the routing of the throttle cable or increase the tension on the return-side cable.
After adjusting the return-side tension, be sure to check the throttle free play again.

Throttle free play and return tension are interdependent.

Throttle Adjustment on the Carburetor Side – Explanation for the FCR Side.

Let’s proceed with the explanation based on the FCR carburetor.
[Red ①] is the pull cable, and [Red ②] is the return cable.
Make sure [Red ①] is adjusted so that the throttle valve opens fully when the throttle is fully opened.
Loosen [Red ②] just enough so that there is no tension. Tightening too much on the carburetor side can cause stiff movement.
Adjust the full throttle position using [Red ①], while [Red ②] is just there to be connected without applying tension.

Throttle free play should be adjusted using the adjuster on the throttle holder side.
Even if [Red ②] is loose, it will be tensioned through the adjustment on the throttle holder side.
If you apply too much tension to both throttle cables, you won’t be able to make the necessary adjustments.
[Red ②] is a mechanism designed to allow you to manually return the throttle in case of a throttle malfunction, even if it's loosened.

Important: Please ensure that [Red ②] is in a state with no tension applied.

[Red ②] is the return throttle cable.
Make sure it is always set to a loose tension. Adjust and tension the throttle using the adjuster on the throttle holder side.
If you loosen [Red ①] first, you won’t be able to adjust the opening and closing of the throttle valve. Always keep [Red ②] at a loose tension.

For vehicles with a dual throttle cable setup, similarly loosen the tension on both standard carburetors.
When you close the adjuster and apply tension to the throttle, only one side should have tension. As long as the return throttle cable is connected, there should be no problem.

Adjustment Method for Single-Pull Throttle Cable

Although not recommended, here’s how to adjust a single-pull throttle setup.
My blog typically assumes a two-cable setup for both pull and return, but if you get the chance, experimenting with a single-pull setup can enhance your understanding of throttle cables.

Adjustments are made using only [Blue ①] and [Red ①].
As mentioned earlier, the return throttle cable should be connected, but it does affect the tension of the pull cable.
While some users opt for a single-pull setup, having a two-cable setup allows you to manually return the throttle in case of issues with the throttle cable.

Is it better for the FCR throttle free play to be as minimal as possible?

Generally, a throttle free play of 5mm is recommended. However, regarding motorcycles equipped with FCR carburetors, my personal view is that a smaller free play is preferable, ideally as close to 0mm as possible.

The reason is that the FCR is a direct-acting carburetor. It directly moves the throttle valve via the throttle cable, offering a direct operational feel. From this perspective, minimizing the free play is beneficial.

However, be cautious as having almost no throttle free play can make the motorcycle difficult to ride on the street, and can even become dangerous. Risks include the throttle opening when turning the handlebars or accidentally hitting the throttle with your hand.

It is essential to check that the throttle fully returns when the handlebars are turned.

After adjusting the throttle cable, make sure to fully turn the handlebars to both the right and left, and verify that the throttle returns smoothly from fully open to fully closed. If the return is sluggish, you may need to adjust the routing of the throttle cable or increase its tension. The best approach is to review the routing of the throttle cable. This step is crucial to prevent potential issues and ensure safe operation.

For FCR Beginners – Be sure to adjust the throttle cable.

Adjusting the throttle cable is an essential task in FCR tuning. As mentioned, the FCR is a direct-acting carburetor, meaning the throttle operation directly influences the opening and closing of the throttle valve. This direct response is one of the highlights of the FCR.

To fully experience this direct operational feel, it is crucial to adjust the throttle free play to your preference. The adjustment is straightforward and should be done properly to ensure optimal performance.

When installing or removing the FCR, the throttle cable is often detached. Take the time to adjust and secure the throttle cable properly each time you reinstall it to ensure a smooth and enjoyable riding experience.

Adjustment of Motorcycle Throttle Free Play【summary】

Throttle adjustment is a task that anyone can handle. It doesn't require any special tools, and even if mistakes are made, they are usually easy to correct. I encourage you to give it a try.

When tuning the FCR, I pay particular attention to the throttle cable tension and synchronization. Additionally, I also make sure to adjust the idle stop screw carefully.

The throttle is something you interact with constantly while riding your motorcycle. By taking the time to make these adjustments carefully, you'll enhance your riding experience and enjoyment. If you haven't checked these adjustments before, I recommend doing so.

See you again!

CBX1000 – Photo Gallery