FCR Tuning – Change slow jet from 40 to 42 – 22/10/08

This article can be read in about 9 minutes.

FCR Tuning – Change slow jet from 40 to 42 – 22/10/08

The other day, I changed the slow jet from 42 to 40.
However, it seemed like we were reaching the limit of retuning the PS, so we changed it from 40 to 42 again.
For me, the best way to do this is to keep the air-fuel ratio at idle from 12.5 to 13.0 when the throttle is fully closed.
It's a boom. It feels like the ride becomes milder, which is good.
I don't see the pros and cons in every situation, so over time I may come across things I don't like, but for the time being I'll be riding the CBX with my current Slow Jet 42.
Repeating the same tuning over and over again will improve the accuracy of your work.
I think the result is okay

Things I tried other than changing the slow jet and things to be careful about

I adjusted the opening of the throttle valve more carefully than usual.
My CBX is equipped with an old FCR.
Two sets of three FCRs are installed.
The throttle wire has two prongs.
I also measured and installed the length of the throttle wire to make the opening of the throttle more accurate than usual.
We checked and adjusted the discharge timing of the accelerator pump so that it would not hit the throttle valve when discharging fuel.
The heights are now the same even when the throttle valve is fully open.
Every time, I try to pay attention to everything.
This time I spent more time than usual.

Current state

[SJ42 screw]
AS-1.40 minutes
PS-3.05 minutes

Acceleration pump diaphragm KLX250
Acceleration pump discharge large ring 2.3mm
AS Uotani SP2-Ignition [1]

Lately I've been idling on lean.
It's good to open the throttle a little and then connect with a solid sense of power.
JN uses the 90FXM that comes with BITO's CBX FCR kit.
This is a special count JN.
Suitable for CBX, but straight diameter cannot be selected.
I feel that the number of clip stages is not appropriate.
The screw is close to its limit.
Since JN has a high round-up, I'm wondering if it will end up with such specifications.
I will consider making SJ even larger.
Either way, if you are interested, the only answer is to change it and try it out.

work photos

I didn't do anything particularly new, but this time I worked more carefully and spent more time.

For FCR beginners – do not change the slow jet easily

Basically, slow jets are not something that should be changed easily.
There are several reasons,
With the slow jet as the parent, the air screw and pilot screw control the area of influence of the slow jet.
If you feel that the air screw and pilot screw are out of range when opening and closing, change the slow jet. The slow jet alone is not used for tuning. Other jet types also have strong complex elements, but it is better to think of slow jets as having two control screws.
Slow jets are more difficult to change than other jets.
Since the chamber is removed, there is a risk of damage to the chamber packing.
Since the chamber is removed, the fuel can drain out.
For CBX, it is necessary to install and remove the carburetor and tank.
If you want to deepen your knowledge, you can change it.
It is affected by the straight diameter of JN and the number of clip stages.
I've made quite a few changes.
Over the course of several years, I tried each one from 35 to 52 on CBX.
I also tried various straight diameters of JN.
I feel like it's getting better, but I can't really tell.
In the end, I feel like I made ends meet with the number of screws and clips.
Recently, I have become more sensitive to changes in PS.
A few years ago, I didn't really understand the changes in PS. There is also the precision of my own work and senses,
I can't feel any specific difference between slow jets.
I feel that the larger the slow jet, the better the blowout.
It's hard to say because it could be due to multiple factors.
For example, when I tried increasing the slow jet and changing the straight diameter of the jet needle to a thinner one, I felt that the blowout improved, but in the end, I may have just adjusted the balance with the screw. not.
So, for beginners, SJ is basically unchanged.
The tuning manual also says to change the screw if it exceeds the range.

FCR Tuning – Change slow jet from 40 to 42 – 22/10/08【summary】

The temperature in Japan was summer-like until the middle of September.
I thought it was a bit chilly autumn today.
The parts that change depending on the season for tuning are MJ and screw adjustment and the number of clip stages.
If you can ride normally without thinking about anything, the tuning is complete.
If you don't tune it, I feel like there will be a change in the acceleration feeling unique to FCR.
Still, there is a good sense of acceleration.
If the rider feels that it is good or wants to stop at this point, it is close to the best tuning or the best tuning.
In the winter, we perform maintenance on the CBX.
While tuning, we will arrange the parts necessary for maintenance and consider a maintenance plan.
I hope you all have a wonderful motorcycle life.
See you again!
Copied title and URL