I am the owner of a Honda motorcycle [CBX1000] who lives in Hiroshima City, Japan. I am posting about FCR carburetor and CBX1000 customization. I also post about things other than cars and motorcycles. We will post information that will make bikers around the world happy.
This is one episode about good things and three parts about failures. It's true that people often learn from their mistakes. So let's get started!
The tuning changes depending on whether you use high octane or regular gasoline.
I've always used premium octane fuel, so this is something I've never tried. I'm glad I heard about it before it made a mistake. The following is written in second person instead of third. First of all, switching between premium and regular gasoline will change the tuning. Premium and regular gasoline have different specific gravities. This means that the weight per 1cc is different. With the same tuning, using premium gasoline will result in a rich sound. FCRs basically require premium octane fuel. The reason is to use fuel efficiently to produce power. It's a racing carburetor, so it's only natural, and after hearing the details, I was convinced that this was probably the case. I haven't tried it myself, but this story seems credible.
The main jet and slow jet can be purchased as a set.
Although they are not genuine Keihin products, the main jet and slow jet are sold as a set. The CBX1000 is a 6-cylinder engine. Collecting all the jets costs six times as much as the SR. I already have 52 jet needles alone. For a small body, if you convert by type rather than number, you can buy 2/3 of the jet needles. Although they are aftermarket parts, if you buy the jet needles and slow jets as a set, you can buy them for roughly 2/3 of the price. It is more efficient to buy a certain amount in bulk rather than buying each type one by one while watching the tuning progress.
The meaning of the oil level adjustment angle and the float valve gauge
This is about adjusting the oil level. The tuning manual states that the body should be tilted about 15 degrees. It doesn't say whether this is horizontal or downdraft. My senior told me that this basically means that you should adjust it at a free angle where there is no resistance from the spring. It's a bit of a rough adjustment method. You can't get a clear measurement in the first place. You can't measure the height clearly unless you buy a float valve gauge and measure it. If you want to measure the float level accurately, you need to use the siphon law with a clear tube.
Do the air screws return differently for each cylinder?
It may depend on the characteristics of the motorcycle, but I will write it based on the CBX1000. The tuning manual states that you should determine the highest RPM for each cylinder. In the case of the CBX1000, you cannot determine this by sound or meter. In my case, I used the same return for each cylinder. After that, I introduced a digital tachometer and adjusted the return for each cylinder to match the point where the RPMs rose, but realistically speaking, there did not seem to be a difference of more than 10 minutes between each cylinder. Currently, I tune each cylinder with the same return amount. There may be individual differences between motorcycles and characteristics depending on the type.
The two-pronged throttle wire requires wire adjustment.
I was so shocked that I could say there's no point in tuning without adjusting the throttle wire. First, open the throttle a little from fully closed, but if you haven't adjusted the throttle wire. The angle at which you start to open is different for the left group of 1 to 3 and the right group of 4 to 5. In other words, there is a difference in how the throttle valve rises on the left and right. The idle stop screw comes into play. And this is about opening it fully, on the other hand. Even when the throttle is fully open, the timing at which it opens fully on the left and right may be different, and even when the throttle is fully open, one of the left or right groups may not be fully open. It may not have much effect on driving, but it can be quite depressing to discover such a fact when you're doing detailed tuning.
Foam Air Filter Sock requires oil
The rate at which the sponge deteriorates is significantly different when filter oil is applied to the Foam Air Filter Sock air compared to when it is not. It depends on the storage conditions, but if oil is not applied, the sponge will turn to powder and begin to decay after about a year. As for the effect on tuning, I have not noticed a big change. The same goes for the Velocity Stack, but there does not seem to be any noticeable change. The air intake efficiency will definitely decrease. At a general level, durability should be prioritized.
Keihin does not sell products that adjust the total discharge volume of the accelerator pump.
It appears that Keihin does not sell tuning accelerator pump diaphragms. They are sold as genuine Yamaha parts with numbers that allow you to change the total accelerator pump discharge volume. Kawasaki has a lineup of genuine parts for different types of motorcycles. And the total discharge volume is also set differently for each model. I think they are purchased from different places.
Tuning becomes more difficult when quick throttle is introduced
This is more of a fact than a failure.
I changed the throttle angle from 90 degrees to 56 degrees.
I thought that 90 degrees would be more difficult to tune because it allows for more precise throttle work.
In reality, quick throttle allows the jet range to switch more quickly and allows for more rapid acceleration. I feel like the difficulty of tuning has increased because I had to tune for acceleration and the jet switching,
and also take into account the effectiveness of the acceleration pump.
Just before I introduced quick throttle, I thought it would be easy to ride and that it would be all good because I could easily twist the throttle up to full throttle.
The advantage is that you can easily twist the throttle up to full throttle.
Making tuning more strict is not a disadvantage.
From this result, tuning with narrow throttle is easier because the changes are more gradual.
I think it’s bad if the acceleration pump timing is too fast.
If the acceleration pump discharge timing is too fast, the fuel will hit the throttle valve directly. The situation is different when the engine is running and when it is not running. It is best to check it visually once. The fuel evaporates, so it may not have any effect on driving, but it is not a pleasant feeling.
Accelerator pump total discharge amount is hourly
It is sometimes stated that changing the accelerator pump diaphragm will change the total amount of fuel. It does not change the force with which the fuel comes out, but the time it takes for the fuel to come out. There may be a change in the force, but it is better to think of it in terms of time. When looking at the tuning manual, it may seem as if the fuel will continue to come out until it is fully open, but in reality, changing the accelerator pump diaphragm will change the time it is discharged. Be careful.
Tuning by the burnt color of the plug
You cannot tune your engine based on the burnt color of the plugs. Checking the burnt color of the plugs is to detect any malfunctions in advance. It is taboo to frequently remove and reattach the plugs for tuning, as this can damage the plug threads.
FCR tuning improves fuel economy
There are pros and cons depending on your point of view. First of all, the FCR is a racing carburetor, so it's not something to worry about fuel efficiency. When fuel efficiency is extremely poor, it's because the tuning is not working properly. Rather than actually improving fuel efficiency, the correct interpretation seems to be that improved riding performance and the rider's feel lead to improved fuel efficiency. I don't drive at low engine speeds to get good fuel economy, so I can't say for sure, but it seems safe to say that an FCR that has been tuned to your own liking will have better fuel economy than an FCR that's not working properly.
Ignition timing affects tuning
My CBX1000 is equipped with the AS Wotani SP2. The ignition timing can be easily changed with a dial. I have felt that this changes the performance of the motorcycle. Here's the tricky part - you need to re-tune it to match the changed condition. It's not that changing the dial improved the tuning, but rather that the tuning before changing the dial was suboptimal. It is also possible that changing the ignition timing can improve performance regardless of tuning.
For FCR beginners – Collect information online and contact the manufacturer
It may be bad manners to inquire at a custom shop. However, it is essential to search the web for FCR information left by your predecessors. It is not bad manners to do so. The web is information without responsibility. Do not take it at face value. There is a high chance that someone has made a mistake before you tried it. You can check in advance. It is bad manners to inquire at a custom shop, but there are exceptions. It is not bad manners to inquire at the place where you purchased the product, such as BIT. The other party will tell you anything that they cannot tell you. If you are doing DIY as an individual, you may not be able to move forward unless you gather information. Take the initiative to gather information.
The surprising moment when I tried tuning my own FCR – for beginners – Failures 3/3【summary】
I may not have written enough yet. I have written down what I can remember about the things I felt I had done wrong since I started tuning FCRs, and the things I would not have wasted time or money if I had known beforehand. One thing I realized again while writing this is that [people learn from their mistakes]. Sometimes mistakes can be irreversible. In my case, tuning the carburetor did not cause any irreversible problems. I made a lot of mistakes, but it was good that I tried various things. I hope this will be helpful for those who are about to start tuning FCRs. See you again!
