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.
Changed the FCR acceleration pump diaphragm. Visual inspection is important. Changes in total discharge volume are difficult to understand
We are doing various tuning on the accelerator pump. I tried various things such as changing the acceleration pump diaphragm and changing the large discharge timing. In terms of driving feeling, you can feel a considerable change. The most noticeable change was when I turned off the accelerator pump.
It is unclear whether the discharge timing has been adjusted accurately with the metal plate. There is no problem if the comparison before and after tuning is done by the same person. To adjust the metal plate in 0.1 mm increments, there is a curve on the measuring part. It is likely that the measurements will be different each time. Highly accurate adjustment is a difficult mechanism. I had a chance to remove the Velocity Stack. I tried changing the accelerator pump diaphragm. Check if there is any change in the total discharge amount. . No exact measurements were taken. I will write about how much change there is visually and my thoughts on it.
Effect of accelerator pump diaphragm change
I am trying to replace the FCR standard accelerator pump diaphragm with the Kawasaki KX250 diaphragm. There is a bulge in the center of the accelerator pump. This suppresses the movement of the accelerator pump diaphragm. You can see the change even at first glance. If you try various changes, you will have more questions about things like how to open the throttle. Before posting the video, I will write a conclusion. If you are conscious, you can see it visually. There is a difference in the speed at which the fuel ends. There is a change in the total discharge amount. If you feel like something is different without concentrating, that's a big amount of change. The straight diameter of a jet needle cannot be determined by looking at it. The driving feeling has also changed. The most noticeable change is the change in the air-fuel ratio meter.
Links to YouTube.
The first half is the standard accelerator pump diaphragm. The second half is the acceleration pump diaphragm for KX250. If you concentrate and look at it, you can see the change.
For FCR beginners – Check the movement of the accelerator pump by operating the throttle
① How does it react when you gradually open the throttle? ② How many seconds does it take for the fuel to be sprayed out in the event of a sudden burst? ③ How can fuel directly hit the throttle valve? ④ Is the range of influence described in the tuning manual correct? In addition to the above four points, you can gain a lot of knowledge just by looking at the individual differences between motorcycles, how the rider opens the throttle, how the riding feels, etc. It is important to know the points to look at first. If you slowly open the throttle, the accelerator pump will not work. If you open too quickly, you will run out of fuel. Even if the metal plate of the accelerator pump is opened more than 5mm, the accelerator pump will not turn off.
Replaced the FCR acceleration pump diaphragm. Visual inspection is important. Changes in total discharge volume are difficult to understand【summary】
I did a casual comparison of the accelerator pump diaphragms this time, but it was more difficult to understand the changes than I expected. I feel like things are changing, but it's only noticeable when I watch the video. It may be difficult to notice the change, but the way you open the throttle can also make a big difference. The measurement method is also ambiguous. I was able to confirm this from the video. I've seen posts on the web saying that the total discharge volume of the accelerator pump is large for single-cylinder or two-cylinder engines. The accelerator pump diaphragm should not be used to control whether there is more or less. The FCR acceleration pump should be controlled by the discharge timing. Or it is better to control it by turning it on and off. My CBX1000 is equipped with a quick throttle. I was worried about the bumps when it opened suddenly. The best solution to this problem was adjusting the discharge timing. It seems that fuel is only being discharged from the accelerator pump when it is suddenly opened. Visually checking how the fluid is being discharged is a part of tuning the FCR. Very helpful. For example, if you gradually open the throttle to full throttle, there will be almost no discharge. The force of suction also differs depending on whether the engine is running or not. You won't notice this unless you actually see it. It's easy if you just look. Please check the behavior of the accelerator pump by operating the throttle once. I hope you all enjoy tuning your FCR. See you again!
