FCR tuning – You can tell whether the accelerator pump is rich or lean with the air-fuel ratio meter.

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FCR tuning – You can tell whether the accelerator pump is rich or lean with the air-fuel ratio meter.

My CBX is equipped with a PLX DM-6 air/fuel ratio meter (A/F meter).
When it comes to measuring the air-fuel ratio meter, which is the subject of this article, it is better to use one with a wide band and high response.
I removed and installed the CBX triple meter analog voltmeter.
Of course, this is to be used for FCR tuning.
The reason I installed it in that position is to stare at the meter.
It is difficult to stare at it while driving.
At least if you put it in a highly visible position, you can easily check the air-fuel ratio while driving.
Motorcycles travel an incredible distance in seconds.
It depends on how you use the air-fuel ratio meter, but it's easier to drive if the meter you check frequently is in front of you. For clocks such as Yoshimura Progress 2, voltage, oil temperature, etc., there are few instantaneous changes in the meter itself, so
There is no problem even if it is placed in a place with poor visibility.

PLX-DM-6, air fuel ratio meter

How to check the effectiveness of the accelerator pump

Rich or lean can be determined by the change in air-fuel ratio when the throttle is suddenly opened.
In addition, if you change the total discharge volume of the accelerator pump by turning it on or off,
You can tell whether the accelerator pump is rich or lean.
Instead of taking 1 second to reduce the throttle opening from 1/8 to 1/4,
It is necessary to change the throttle opening from 1/8 to 1/4 in 0.01 seconds.
It is necessary to try a rapid opening pattern that is likely to be used in the driving scene, such as a throttle opening of 1/8 to 1/2.
When you gradually open the throttle, the fuel from the accelerator pump is also gradually discharged, so
I don't know if it's working or not.
Tuning on the FCR jet controls the mixture ratio.
The accelerator pump works on the same principle as a water gun.
This refers to how many seconds and with what force the water gun was used to supply fuel to the combustion chamber of the engine.
The larger the throttle opening is, the more fuel is delivered in a short period of time, so it is necessary to reduce the discharge amount of the accelerator pump or change the timing of the start of discharge.
It also depends on how each rider uses the throttle. Also, if you change the throttle to quick throttle, the discharge amount of the accelerator pump increases by operating the throttle rather than mechanically.

When you open the throttle quickly, the air-fuel ratio becomes lean.

The carburetor uses the negative pressure that sucks in air when the engine piston moves down to feed the air-fuel mixture into the engine. It is more correct to say that the engine is sucking the oil rather than pumping it.
If you open the throttle quickly and the throttle valve opens a lot, a lot of air will be sucked in.
In theory, if you open the throttle quickly, the air-fuel ratio meter will show a lean value.
The accelerator pump discharges only fuel directly to the engine without using the engine's negative pressure.
Since it does not use the negative pressure of the engine, it is possible to directly make the air-fuel ratio rich.
If you look at the air-fuel ratio at that time, you can see how much the accelerator pump is correcting the air-fuel ratio.
If the engine becomes rich even when the throttle is opened rapidly, the accelerator pump is working too strongly.
If you want to become lean, try speeding up the discharge timing first.

accelerator pump is fun

When the accelerator pump is working well and you roughly operate the throttle while riding the motorcycle, you can experience a tremendous sense of acceleration and it's very fun.
In the case of my CBX, I didn't notice it before I installed quick throttle, but
After installing the quick throttle, I started to notice the symptoms of sluggishness caused by richness with the accelerator pump.
At first I didn't realize that something was wrong, but
Before I knew it, I was running better without the accelerator pump.
FCR is not very good at controlling the acceleration pump.
The accelerator pump always operates when the throttle is opened.
The FCR's accelerator pump is a rather sloppy mechanism when it comes to tuning.
It is not a mechanism that can be precisely controlled.
There is also no mechanism like the TMR carburetor where the accelerator pump only works when the throttle is suddenly opened.
Tuning that assumes there is an accelerator pump may not be good.
However, a motorcycle with a well-functioning accelerator pump is extremely fun to ride.
There is no mistake.

For FCR beginners – take notes after adjusting the accelerator pump plate

This is a warning to beginners as it can be a pitfall.
Regarding the discharge timing of the accelerator pump.
Beginners probably tend to just change the width of the adjustment plate while doing a test run.
If you change the adjustment plate for the discharge timing of the accelerator pump, please record the work history.
I keep the history in Google spreads.
It is useful for tuning to record how many mm you changed the adjustment plate.
When I ride a motorcycle for the first time in a while, I don't remember what I did last time.
Keeping a work history, even just the start and end of the day, can be helpful when replacing other jets.

FCR tuning – You can tell whether the accelerator pump is rich or lean with the air-fuel ratio meter.【summary】

An air/fuel ratio meter is also useful for replacing fixed jets.
However, I also feel that we should not get caught up only in air-fuel ratio meters.
Perhaps because it is difficult to precisely tune the accelerator pump, an air-fuel ratio meter is extremely useful.
Rich and lean, fast and slow are easy to understand numerically. If you get rich all at once when you open up quickly, the accelerator pump is working. You can see it with your eyes. How effective is tuning just by feeling it?
Is it working properly? First of all, I don't know.
I can tell when the feeling of acceleration is slow, but I can't tell if it's starting to work properly.
Maybe you'll understand once you become a veteran.
As a beginner, I don't know.
You should use an air-fuel ratio meter to tune the accelerator pump.
If you are having trouble with your accelerator pump, we strongly recommend that you install an air-fuel ratio meter.
Then see you again!

*Recent CBX photos are posted at the bottom.

CBX Photos

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