Scope of influence of FCR’s MJ main jet

PLX-A/F meter FCR
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Scope of influence of FCR’s MJ main jet

I will write about the fact that I replaced MJ the other day.
This is the content when I changed MJ from 118 to 128 as a test.
It is better to take a look at these first.
mj influence range
mj influence range
The number is 10 different and it says that the fuel was increased by 15% last time. I understand that if the number is different by 10, the air fuel ratio will be different. As for the range of influence, I felt that it affected up to about 1/4 of the throttle.

FCR tuning change

1.15 minutes
1.0 minutes


Recently, I prefer richer tuning, so I try to keep it between 11.5 and 13.5 while accelerating.
I'm trying to aim for 12.5 to 13.0 as much as possible.
I try not to worry about it even if I get into 11 in a partial.
I prioritize the experience and try not to worry about the air-fuel ratio even if it reaches a very extreme value.
I was aiming for 12.5 in partial, but
It's more fun to ride when it accelerates to 12.5 while accelerating.
I was also thinking of lowering the clip or tuning the PS back a little by 15 minutes.
I've been poking around a lot lately, so I tried to change the number of clip stages while also getting in sync.
However, there was a surprising change in MJ alone.
I have not tried driving at full throttle.
The overall throttle opening is soft, not just 1/2 but 1/4.
I felt like it was getting richer.
I was thinking of changing the number of clip stages on JN or changing the straight diameter.
However, since the current tunings were very good, I decided to just replace MJ.

For FCR beginners

We recommend installing an air-fuel ratio meter [A/F meter]. An amateur cannot tell by looking at the color of the plug.
You can check the plug when the engine is idling if you really want to.
If you feel that 10.0 or 14.0 is fine based on your experience, you can ignore it and make your decision if it is 12.5 while accelerating. If experience is not prioritized, the partial air-fuel ratio will be recognized as the current air-fuel ratio, resulting in a lighter tuning and a fuel-efficient tuning that lacks a sense of acceleration. Consider the throttle opening rather than the rotation speed or gear. The manual doesn't mention the RPM except when idling. Items that are not described in the manual and should be referred to are:
This is when the load is applied to the rear wheels. At the moment when you engage the clutch, on a slope, or when you suddenly open the engine, the fuel gets leaner and you need to let the fuel catch up. It is better to take into consideration the load placed on the wheels.
This is the reason why the acceleration air-fuel ratio and the partial air-fuel ratio can be considered separately.
Write the terms below.
Output air fuel ratio 12.5
Theoretical air fuel ratio 14.7
Accelerating - A state in which the speed is increasing.
Partial - steady state
1.15 minutes - It means tuning a screw, likening it to the hands of a clock.
Number of clip stages of #2-JN counted from the top. It means the second row from the top.

MJ exchange

I moved the carburetor, but since there is some tension in the wires, I will replace it without disassembling it as much as possible.
MJ can be replaced from the drain part for removing gasoline. Since it is made of brass, when working with no look, be careful not to overtighten and tear the MJ.

CBX-carburetor synchronization

Please synchronize the carburetor to the best of your ability.
In my case it was completely gone.
If the work is done frequently, the idea is that 95 minutes is enough. Rather, we make sure to perform thorough checks such as how the valve opens when the throttle is fully open and how well the throttle returns.

Scope of influence of FCR’s MJ main jet【summary】

MJ's influence is bigger than I imagined.
This is a new discovery.
I feel that the current FCR is in very good condition.
If you make tunings based only on the numbers on the air-fuel ratio meter, you may not get the best tunings.
There have been so many positive changes that I wonder what I've been doing up until now.
I'm not doing any research on FCR, but I'm just playing around with it out of my own interest.
At present, we are not testing the case of adding a richer count.
It is best to keep in mind that the exchange of MJ and JN will greatly influence each other.
In the future, we will take into consideration the influence that MJ will have on the whole when making tunings.
I hope you all have a wonderful FCR life!
See you again!
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