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.
Is an FCR accelerator pump necessary? This debate is very difficult because it involves many different conditions. You want to make effective use of what you can use. Keihin also uses this mechanism because it is necessary. It is said that single engines such as the SR have too much total discharge. I think that the timing at which the discharge starts should be determined more strictly than the total discharge. And I don't think it is necessary for tuning my CBX1000 at the moment. I feel that it would be better to have the accelerator pump turned off and then turned on after a while. This symptom appeared after I set the quick throttle. If I set the discharge timing to about 1/4 throttle opening, even if I reduced the amount, it became a rich symptom. Currently, I set it to start working at about 1/2 throttle opening. I feel that it is not affected by sudden opening at low throttle openings. Either way, even if you tune based on the discharge of the accelerator pump, I don't think it will be a severe tuning because it is a somewhat approximate mechanism. In addition, the mechanism significantly affects each rider's throttle operation, with some riders opening the throttle suddenly and others slowly and gradually. I will write about the acceleration pump from the perspective of the CBX1000.
Accelerating pumps measure discharge time rather than total discharge volume
There is a slight misunderstanding about the total discharge volume of the accelerator pump. The accelerator pump can be tuned for the following two things. ① At what throttle opening does discharge start? ② For how long does it discharge?
Let me explain. ① can be easily controlled. ② is the total discharge volume of the accelerator pump, but the amount discharged per second does not change. The momentum may change, but the amount discharged per second does not change significantly. As you can see by looking at the nozzle, replacing the accelerator pump diaphragm changes the discharge time. Of course, it will also be affected by how hard the push rod is pressed. It is difficult to say that a smaller total discharge volume of the accelerator pump is better because it is a single engine. Also, since the total discharge volume cannot be strictly controlled, there is a limit to adding fuel in any amount at any location.
We believe that an FCR accelerator pump is not necessary during tuning.
It depends on the tuning method. I think it's better not to use the accelerator pump when tuning the CBX1000. In particular, if the accelerator pump starts to discharge before the throttle is half open, it will usually be too rich when you try to open it quickly. I was tuning it while feeling that something was not right. By turning off the accelerator pump, I was able to realize that the accelerator pump was getting in the way. There is also a way to tune it under the assumption that the accelerator pump is working when the throttle is low. In the case of my CBX1000, I have installed quick throttle. Currently, the accelerator pump starts to work at about 1/2 throttle opening, so the response is not bad when opening it quickly, and the air-fuel ratio gauge no longer shows rich values for no reason.
The feeling of the acceleration pump changes depending on how the rider operates it.
When operating the throttle, there are moments when I feel that the accelerator pump is working. I think that the fact that there are moments like that means that the accelerator pump is a necessary mechanism for the carburetor. With the way I ride, when I use the throttle at 90 degrees all the way up to full opening, I haven't been particularly aware that the accelerator pump is working too well. However, with my current throttle at about 56 degrees all the way open, there are moments when it works too well and I get into trouble.
Does the CBX1000 require an FCR accelerator pump?【summary】
Having written the above, I feel that when the accelerator pump is too effective, the solution is to either change to a narrow throttle, ride carefully so as not to open the throttle too sharply, or change the accelerator pump diaphragm. Riding a motorcycle with the throttle open suddenly is also a lot of fun, so I am currently experimenting with slowing down the timing and reducing the total discharge volume. I have over a year's worth of tuning data for the jets. I would like to change the accelerator pump diaphragm and discharge timing in sequence in early spring until I can find the accelerator pump tuning that is best for me.
