Verifying the impact of CBX PS

FCR-PS-Fully closed air-fuel ratio meter FCR
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Verifying the impact of CBX PS

I have verified the effectiveness of the PS pilot screw for CBX's FCR33 pie, so I will write about it.
To put it simply, I touch the PS and watch the changes in the air-fuel ratio meter while the engine is running.
Please note that there may be problems with personal subjectivity and verification methods.
As a premise,
① When tuning the screws, touch them in the same order from No. 1 to No. 6.
② Although the idling and air-fuel ratio are listed, they may not be correct values.
③FCR may not be in perfect condition.
④It may not be the 1300RPM specified in the manual.
⑤If you turn the PS while the engine is running, the rotation speed will change for about 20 seconds.
I'm checking to see if it exists.


・There is a change in the air-fuel ratio during normal idling.
・Even with the PS fully closed, the engine starts, keeps idling, and runs normally.
- After warming up, the air-fuel ratio is 13.0 when fully closed at about 1500 RPM and 10.8 when the PS is turned back 3.00 minutes.
・If you turn the PS about 2 revolutions, you will notice a change in idling. I couldn't get the feeling that it was being turned little by little.
・It may be a placebo, but low negative pressure when cold has an effect on idling maintenance and starting performance.
・Idling stopped when I turned the stop screw to the limit to maintain idling and fully closed PS from 1.0.
・It may be a problem with the SJ count, but the RPM did not change drastically when opening and closing PS or opening and closing AS.

FCR idle RPM

① Is it the height of the throttle valve?
②Is it the number of revolutions?
③Is it the strength of the negative pressure?
I thought that one of the above would cause PS to work or not.
I was able to see a change in PS during normal idling. The degree of PS change may change depending on any of ①, ②, and ③, but it is usually effective when idling, so I don't particularly care about it at the moment.

Unclear point

① Is it easier to understand the effectiveness of PS when the negative pressure is low?
② Will there be an area where PS does not work depending on the height of the throttle valve?

Regarding the above two points, I will keep them in mind when changing or doing SJ and will verify them when I can. Does the height of the throttle valve affect PS? Is it because of the way negative pressure is applied?
I don't know. At least adjust the stop screw so that it can idle normally.
When the PS was turned, a change was seen on the air-fuel ratio meter. There must be some way to determine the appropriate PS, such as checking the return when the throttle is spun, so I would like to be careful when tuning it.

As a conclusion to the effectiveness of PS

PS is active when idling. It works at least at rotation speeds of 1300RPM-1500RPM.
It may be that after a certain level of concentration (retuning the PS) there will be almost no effect.
The air-fuel ratio that feels good at clutch engagement is around 11.9, so it might be a good idea to adjust it with PS.

PS effectiveness for each motorcycle

According to a senior who works in the Z area, you can clearly see the changes in PS.
God, who built the engine for my CBX, also says that the changes in the PS are clearly noticeable.
Each motorcycle has its own characteristics, so at this stage there will likely be changes in CBX.
The conclusion is that it is difficult to understand clearly.
I've heard that 4 cylinders and 2 cylinders like Ducati are easy to understand.

Verifying the impact of CBX PS【summary】

For several years now, I have had doubts about the effectiveness of the CBX PS pilot screw.
The reason is that I had to stop the engine, remove and install the carburetor, and then turn the PS.
Now that I can check the air-fuel ratio and turn the PS without stopping the engine,
Although it is difficult to understand the effect of PS on CBX, I am certain that it is effective.
I'm starting to get a vague idea of how effective it is. Naturally, how to choose and ride an SJ
There will be various changes as well.
Rather than verifying whether there is a change in the invisible state, I was able to find out that there was a change numerically, which was a huge benefit for me this time. Up until now, when I touched the PS pilot screw and felt that there was a change, it was not a placebo effect.
I was really worried about changing the PS pilot screw, and I changed the SJ one step at a time from No. 35 to No. 55.
Even if I try changing it and trying various things, I can only get a fluffy feeling.
was. There are many machines that have FCR installed on CBX.
Please use this as a reference.
I hope you have a good FCR life!
See you again!
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