For FCR Beginners – Don’t use the red Velocity Stack on the street as it is!

For FCR Beginners – Don’t use the red Velocity Stack on the street as it is!

When you purchase an FCR, it comes with a red Velocity Stack. The small version is red, while the large version is blue. My CBX1000 features the small FCR with a 30mm red plastic Velocity Stack. This Velocity Stack can be considered the "muffler" on the air intake side, as it is a necessary component for streamlining airflow.

In this post, we’ll explore how to modify or replace the red Velocity Stack that comes with the FCR. A concerning trend I’ve noticed among those who install racing carburetors like the FCR is that they often leave them untouched. With the standard red Velocity Stack, you risk sucking in debris, and it’s not suitable for riding in the rain. Additionally, you won’t be able to properly adjust the air screw.

Having an FCR and not doing anything with it results in a state that is simply “installed.” Since the FCR is a carburetor meant for tuning, it’s important to make some adjustments. If your aim is to restore your bike, you should definitely consider installing a filter as well.

There’s a difference between not touching it at all and being unable to do so. Using an FCR on the street draws attention, so you might as well want to be seen in a good light.

In this post, I’ll discuss the best ways to handle the red Velocity Stack once you’ve installed the FCR. So, let’s get started!

Simply installing an FCR for aesthetic purposes is actually a downgrade.

You must not forget that the FCR is a racing carburetor. Unlike professional racers who can quickly use new ones, average users may not have that luxury. The true essence of the FCR lies in its maintainability and tunability.

Regarding the topic of this blog post, the red Velocity Stack, the key point is its use in street applications. While it’s perfectly fine to use it as is for racing, if you're using it on the street, you should definitely install a filter. The Foam Air Filter Sock on the red Velocity Stack offers an easy dust protection solution.

Using a brand-new carburetor with the original red Velocity Stack on public roads doesn't align with the intended use of the FCR. If you're using the FCR because your standard carburetor isn’t performing well, having a filter is essential.

If you're just dressing up your bike with the FCR, I would recommend swapping it for something more polished, like an aluminum Velocity Stack. If your engine or FCR starts to underperform, you can always throw money at it to fix the issues.

A red Velocity Stack that is left unmodified typically conveys a clear message: it shows a lack of both time and investment in the setup.

The red Velocity Stack is used as an adapter for modifications and for the Foam Air Filter Sock.

The use of the red Velocity Stack is to serve as an adapter for modification or to install a Foam Air Filter Sock. If you want to ride filterless on the street, it’s a good idea to choose an aluminum Velocity Stack or your preferred size as part of your tuning. In the case of my CBX1000, I need to modify the Velocity Stack to install the Foam Air Filter Sock. However, I feel hesitant to buy an aluminum Velocity Stack just to modify it for the Foam Air Filter Sock. In this respect, the plastic red Velocity Stack is easier to work with, allowing you to freely drill holes or make other modifications to adjust the air screw.

The length of the Velocity Stack is a tuning item.

It is said that a longer Velocity Stack is better suited for low RPMs. Conversely, I've heard that a shorter Velocity Stack is better for high RPMs. I'm not sure if this is true. I wonder if a longer air passage at low RPMs helps create more momentum when drawing in air. I also think it’s better to have good airflow at high RPMs. So, a longer Velocity Stack might be preferable. However, when reaching high RPMs, the length of the Velocity Stack may not affect performance, and there might be reasons why shorter stacks are better.

In any case, selecting the length of the Velocity Stack is one of the tuning considerations. My CBX1000 is equipped with a 50mm Velocity Stack. I have not tested the difference between a 30mm and a 50mm stack. There might be noticeable differences if I pay attention while riding. If you're primarily riding on the street and considering changing the length of the Velocity Stack, I recommend choosing one longer than the initial 30mm.

There are large and small Velocity Stacks.

There are two types of FCR: large and small. If you include horizontal and downdraft configurations, there are a total of four types, but for now, I want to emphasize that there are large and small versions. The size of the Velocity Stack also comes in two variations corresponding to large and small. The diameter of the FCR itself is not the main concern. You only need to pay attention to whether your motorcycle's FCR body is large or small.

What air filter will you choose?

I seriously recommend using a power filter or a Foam Air Filter Sock. If you absolutely want to go filterless with the red plastic Velocity Stack, you're likely a veteran who knows engines and carburetors inside and out. You should be someone who can perform maintenance immediately if you’re unhappy with the performance or if things start to go wrong. Wealthy individuals who think it's fine to replace things as soon as they break will likely spend money on Velocity Stacks as well. If you're using the FCR on the street, please use a K&N power filter or a similar product. Filters that cover the Velocity Stack are also effective for dust protection. Even if you apply a lot of oil, it won’t particularly affect your riding. There's also little chance of getting your motorcycle or pants dirty.

I’m concerned about fires with the Foam Air Filter Sock.

I apply filter oil to prevent fires. It also extends the lifespan of the Foam Air Filter Sock and enhances its dust filtration performance. Installing a Foam Air Filter Sock without applying filter oil only adds one more risk. If a fire were to occur, it would be disastrous, so please make sure to always apply oil to the Foam Air Filter Sock.

Riding without a Velocity Stack (direct carburetor).

There is no problem riding with a direct carb setup without a Velocity Stack. I haven't tried it until I encounter issues. Riding without a muffler is too loud to be practical. Without a muffler, it results in a hollow sense of power. It's also questionable whether the engine can function properly in that state. The Velocity Stack is something that should be installed, which is why it comes included. I don’t see motorcycles running without a Velocity Stack. Moreover, if you install a K&N power filter, it will have a shape similar to that without a Velocity Stack, which also reduces the rectifying effect of the Velocity Stack. If the engine operates at low RPMs, the effect of the Velocity Stack might be minimal.

A direct carb setup with a Velocity Stack produces more power.

Until recently, I thought that whether or not a Foam Air Filter Sock was installed, or whether it was a Velocity Stack setup, there wouldn’t be much difference. However, when you use a direct carburetor on smaller displacement motorcycles, you can sometimes get more power than expected. In the case of the CBX1000, when I consciously focus on my riding, I do feel that the direct carb setup offers a greater sense of power. The CBX1000 is a large displacement motorcycle, so the difference might have been less noticeable initially. Currently, I believe that going filterless provides a better sense of power. However, it's hard to say there is a significant change in the air-fuel ratio.

A motorcycle with a red plastic Velocity Stack on the street looks uncool.

Before I started working on the FCR myself, I thought it looked cool and race-ready. However, after I began tuning the FCR myself, I find it less appealing when I see an FCR that hasn't been properly adjusted. Even for motorcycles fitted or tuned by a shop, I often assume they've only made minimal adjustments to the air screw. If a shop has seriously tuned a motorcycle, there will usually be some modifications around the Velocity Stack. Motorcycles with adjusted or modified Velocity Stacks are fast when you ride with them. They also tend to run smoothly and look cool. Just as appearance is important for people, a motorcycle’s look can also give away a lot of information.

For FCR Beginners – You can’t turn the air screw with the red Velocity Stack as it is.

With the 30mm length of the red Velocity Stack, it’s quite difficult to properly adjust the air screw. The air screw and the jet needle clip positions are elements that can be adjusted immediately from the moment you purchase an FCR. No special tools are required. Depending on the shape of the motorcycle, it might be impossible to turn the air screw with the 30mm red Velocity Stack. You may need to make modifications, such as drilling a hole in the red Velocity Stack. Removing it each time is also an option. In any case, there are a few drawbacks. You’ll need to either install a longer Velocity Stack, drill a hole, or remove and reattach the Velocity Stack every time you adjust the air screw.

For FCR Beginners – Don’t use the red Velocity Stack on the street as it is!【summary】

I recommend using a filter on the street. If you are someone who absolutely doesn't want to use a filter, you must be quite knowledgeable about motorcycles. For those who are not well-versed in motorcycles, going filterless is not advisable. Personally, I don't want to ride a motorcycle without a filter. Riding with just the Velocity Stack and no filter is something I only do for a short time during tuning, when I need to frequently adjust the air screw. A motorcycle equipped with an FCR and still in its initial state with the red Velocity Stack is likely not fully tuned. There may also be cases where riders temporarily remove the Foam Air Filter Sock just to put in some extra effort during a touring ride. In any case, the Velocity Stack is one of the tuning elements. Riders who haven’t adjusted their FCR should consider changing the Velocity Stack. It might be the starting point for your FCR tuning. See you again!

I will post related photos from previous entries.

The red Velocity Stack also gives a sense of having an FCR installed. As for the red Velocity Stack, I’ve shaved the sides to be able to fit a Foam Air Filter Sock. Due to the pitch, you need to cut the sides of the Velocity Stack on the CBX1000 to fit the Foam Air Filter Sock. I regularly apply filter oil to the foam.