About engine overhaul of CBX1000

The popularity was split between the 70s and 80s, and currently the Z series has a larger market share, but I'll write about the differences. The main difference between the CB-F and Z series engines is the number of valves. The Z series has two valves, while the CB-F series has four. Putting aside the things that are not immediately accessible or visible, such as a strong engine or powerful output, it all comes down to this one point.

FCR Tuning – Should the Slow Jet Be Changed According to the Season?

Tuning the FCR requires adjustments based on the weight of air and fuel. As the temperature drops, the density of the air increases, making the air heavier. In response, it is necessary to either increase the weight (amount) of the fuel or reduce the amount of air.

FCR Tuning – To What Extent Should Carburetor Synchronization Be Done?

How Far Should Carburetor Synchronization Be Done?When performing synchronization using a vacuum gauge, there are graduations to consider.Is it acceptable for the reading to be off by one graduation?Does even the width of the black line on the gauge count as an error?There are many questions. Recently, I was able to hear the answer from the legend, Mr. Bito.

With the FCR, you can start the engine even on early winter mornings.

I will write about starting the engine of a motorcycle with a carburetor in the early winter mornings. Logically speaking, the Honda Cub, which was commonly used for newspaper delivery in the past, starts the engine easily with the choke and kick start, even on cold winter mornings. Now, regarding motorcycles equipped with FCR carburetors, they don’t have a choke, but you can use the accelerator pump as a substitute. By twisting the throttle about three times and then waiting for about 10 seconds before turning on the starter motor, the engine starts up normally.

re the standard brakes of classic motorcycles low in performance? I customized my brakes.

Comparison of brakes from the past and present: Even when comparing a CBX1000 equipped with a recently manufactured complete brake system to a CBX1000 that is using well-maintained, 40-year-old brakes, the performance difference is significant.

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. It’s a 30mm red plastic Velocity Stack. The Velocity Stack of the FCR can be considered the 'exhaust' on the intake side. It is an essential part for smoothing the airflow.

FCR Tuning – When changing the straight diameter of the jet needle, also adjust the clip position.

When you change the straight diameter of the jet needle, you may need to change the clip position as well, or else the performance can become quite poor. It’s difficult to specify exactly how many steps you should change the straight diameter before adjusting the clip position, but it seems reasonable to think that changing the straight diameter by about five steps would correspond to a change of approximately one clip position.

Is it true that classic cars are prone to breaking down? As long as the engine is intact, it can be managed.

For those of you who are contemplating whether or not to purchase a vintage motorcycle, I think this is an interesting topic. My conclusion is that as long as the engine is running, it can be managed. If you aim to faithfully reproduce the looks and performance of the motorcycle when it was new, maintaining it might be impossible, but if the goal is simply to ensure it runs smoothly, the challenges become much easier to overcome.

The recommended installation position for the air-fuel ratio gauge is at the center of the meter.

Where do you all mount your air-fuel ratio gauges? The air-fuel ratio gauge needs to be carefully monitored during high-speed runs, especially on straight stretches of road where it’s crucial to check the readings. On my CBX1000, I’ve removed the stock voltmeter and positioned the air-fuel ratio gauge right in the center of the meter cluster for easy visibility.

FCR Tuning – Changing Slow Jets, Adjusting Air Screw and Pilot Screw – 2023-11-09

It’s important to make adjustments to the FCR as soon as you notice something off. I’m considering adjusting the throttle low opening screw range and the air-fuel ratio at wide open throttle to be about 1.0 richer. I changed the Slow Jets (SJ) and Main Jets (MJ). This year, I decided not to change the SJ.

FCR Tuning – If the pilot screw is set to 1.00 turns out, it may not be adjusted sufficiently.

In FCR tuning, the initial values for the screws are typically set to an air screw (AS) of 1.00 and a pilot screw (PS) of 1.00, as stated in the tuning manual. This content suggests that there might be an additional level of power available even after achieving what seems like the best tuning.

I went to the 2023 – 11th BITO JB-POWER Meeting.

I attended the 11th JB-POWER Meeting on October 29, 2023 (Sunday). I will focus mainly on the atmosphere of the venue. Photos are compiled at the bottom, separate from the text. My personal reflections will be kept modest, and I will primarily guide you through the venue's ambiance.

FCR Tuning – Regularly resetting the air screw and pilot screw can improve performance.

The FCR air screw and pilot screw are parts that can be adjusted continuously. In contrast, the slow jet and main jet needle can only be adjusted with specific sizes. The air screw is easily accessible once you remove the filter or velocity stack, making it straightforward to observe changes.

FCR Tuning – Having an air-fuel ratio gauge is useful for adjusting the pilot screw.

Having an air-fuel ratio gauge (A/F meter) is convenient for FCR tuning. Even without a gauge, you can achieve precise settings through real-world riding once you get accustomed to it. You can adjust mid to high-speed settings based solely on your feel. In fact, it might be better not to get too caught up in the numbers. However, it can be challenging to determine whether the throttle opening at low speeds is functioning well or poorly.

Does the scope of the FCR tuning manual affect the throttle opening or the valve opening?

This is regarding the scope presented on page 8 of the FCR tuning manual. This page indicates the impact range of tuning, but it raises the question of whether the X-axis refers to the throttle opening or the valve opening. This is something I posted about recently; the throttle opening and valve opening of the FCR are not directly proportional.

FCR Tuning – To what extent does the main jet affect the throttle opening range? – 2023-09-19

I'm describing the effects of changing the main jet, focusing on how it influences throttle positions other than full throttle. After changing the main jet, I went for a test run. My assessment is centered around the changes observed from around half-throttle to three-quarters throttle rather than focusing solely on the full throttle range.

FCR Tuning – Adjusting Accelerator Pump Discharge Timing and Straight – 2023-09-12

I’m framing this as fine-tuning rather than tuning in the strictest sense. The tuning of the FCR is the result of repeated A/B testing. It’s a process of searching for jets that improve performance, and then finding even better jets from those improvements.

The throttle opening and throttle valve opening of the FCR carburetor are not directly proportional.

Even when the throttle is opened to 1/2 on an FCR, the throttle valve on the FCR does not open to 1/2. This is not specifically mentioned in the FCR tuning manual. Knowing this might change your perspective on the operation of the FCR throttle. At 1/2 throttle opening, the throttle valve is typically open only about 1/4.

With the quick turn throttle housing, you can set the throttle free play to 0mm!

When installing a quick turn throttle, one feature that is not present in a standard throttle housing is the throttle stop screw function. Although it might sound elaborate, it is simply a screw hole that has been cut. It is a bolt used to adjust the minimum return position of the throttle.

Throttle grip wiring – The FCR is a push-pull carburetor. Its direct operational feel is very appealing.

For adjusting the throttle area, there's no problem at all in thinking that you can easily do it yourself without needing to rely on a professional. For such tasks, you can usually find methods by searching online. If you still have trouble, you can consult a local motorcycle enthusiast, and you’ll likely find a solution.

FCR Tuning – Testing 6 Variations of Accelerator Pump Diaphragm – 2023-08-22

One of the highlights of FCR carburetors is the accelerator pump. This time, instead of making just minor adjustments, I performed tuning with all the diaphragms I have on the same day. The accelerator pump diaphragms tested were Standard, KLX250, and KLX400, with discharge timings of 1.0mm and 0.5mm, resulting in a total of 6 different patterns.

Adjustment of Motorcycle Throttle Free Play

Throttle Free Play Basics. The standard throttle free play is typically set to 5mm. Additionally, it’s essential to ensure that the throttle returns properly when the handlebars are turned left and right. This ensures that the throttle operates correctly and safely.

FCR Tuning – Adjusting the air screw to the appropriate setting after changing the slow jet – 2023-08-13

The position of the air screw has been adjusted to slightly less than 0.30 minutjes return. The pilot jet has been changed from 45 to 48. This air screw setting in summer may not be ideal for winter, as it would likely need to be adjusted (tightened) during colder months.

How much gasoline is accumulated in the float chamber of the FCR carburetor?

For the FCR carburetor on the CBX1000, it holds about 100cc to 150cc. I took some photos when I changed the slow jet. I will be discussing how to handle gasoline when changing the main jet or slow jet on the FCR carburetor.

FCR Tuning – Re-synchronization after adjusting the throttle cable – 2023-08-01

I synchronize the FCR carburetors on my CBX1000 more than 10 times a year. Whether 10 times is a lot or not, I’m not sure. It’s not that I feel the synchronization has drifted while riding and then correct it. Rather, it’s because minor misalignments occur when I perform tuning and have to remove and reattach parts.

FCR Tuning – Tuning the main jet at full throttle is fun.

As you gradually open the throttle from a low position, you will adjust the relevant jets and screws. Once the low-throttle setting is in good condition, the main jet (MJ) is often already in a good or near-good state as well

Spark Plug Replacement – The Idling of Carbureted Engines Smells Like Gasoline

If you feel that the idling is off, replacing the spark plugs and then re-tuning is a viable option. Tuning involves various interconnected factors, and the spark plugs might be one of the causes of irregular idling. By replacing the spark plugs, you eliminate one potential concern.

FCR Tuning – Adjusting the Jets Slightly Leaner for Summer

When discussing carburetor tuning, terms like "rich" and "lean" are often used. These terms can be a bit confusing for beginners.

FCR Tuning – Full Throttle! How lean can the main jet go? Will the engine hold up?

I have performed full-throttle runs with a main jet size of 102 on my CBX1000.This is a discussion about how lean the main jet can be set based on past experiences.I should clarify that I haven’t tested it to the point of damaging the engine, and the testing is therefore insufficient. The inadequacy of the testing is due to the fact that it has not been tested until the piston melts.

3 Reasons Why Used FCR Carburetors Can Be Used

When you perform the overhaul yourself, it generally ends up being quite cost-effective. This is specifically if you handle the overhaul personally. If you don’t have jets and other parts on hand, it's recommended to use the Carburetor Parts Kit for FCR - KEYSTAR. If you already have some FCR parts, you can buy individual parts separately and complete the overhaul that way.

FCR requires a filter for street use. Constant use of a velocity stack is not recommended.

This applies not only to FCRs but to all carburetors in general: going filterless on the street is not recommended. This is because it sucks in debris. I will write a column discussing why it’s better to avoid this and what you should do instead.

FCR Tuning – Acceleration Pump Discharge Timing Adjustment – Finalized as is – 2023-06-20

FCR Tuning for CBX1000. I was concerned about the discharge start position of the acceleration pump, so I conducted a test ride. As a result, I ended up making changes and then reverting to the original settings. There wasn’t much noticeable difference.

FCR Tuning – Test Ride with Awareness of Shift Position – 2023-06-17

I'm still not quite able to tune it perfectly yet. Recently, I had the opportunity to ride on the highway. During the ride, I noticed something: I realized that I haven't been tuning with much attention to the shift position.