FCR tuning – Considering the seasons of summer and winter when touching AS and PS – 2022-09-17

FCR tuning – Considering the seasons of summer and winter when touching AS and PS – 2022-09-17

Adjustment of AS air screw.

[tuning]
SJ-42
PS-2.25 minutes return
AS-2.30 minutes return
JN-90FXM#2
MJ-128
Uotani ignition timing 1
Acceleration pump diaphragm is KLX250
Discharge timing is 10mm

This doesn't mean it's the best, but
I haven't touched FCR for a while, so I need to be a little more conscious of the end of summer and the beginning of autumn.
What is especially good about SJ?
What level of AS is appropriate?
I hope I can find it on my own.
Regarding SJ with low opening tunings, AS and PS can be adjusted throughout the year unless JN is changed.
I think it would be nice if we could deal with it.
With the above tunings
I think SJ42 is big.
There is no problem with SJ as it is, but I will try it with 40 or 38.
I'm changing AS in various ways to see how it changes.
Given the current situation, I think I would choose between 38, 40, and 42.
I haven't tried 38, so I'll decide whether to settle on 40 or 38 after trying 38.
In either case, the screw is too far back.

Considering the summer and winter air-fuel ratio of FCR

This time, I touched on FCR after a short period of time.
Summer is completely over and we are now in the beginning of autumn.
As a street user, I think there are three ideal conditions for FCR.
①To check the degree of decline, just touch AS and PS.
② Change JN's clip by one level
③ Change MJ if you feel like it is fully open

It is best to be able to complete the tunings with just JN, AS, and PS.
SJ doesn't want to be touched throughout the year.
The reason for this is that changing SJ requires a lot of man-hours.

The tuning theory is that the gasoline in the carburetor becomes richer in the summer and leaner in the winter. The air-fuel ratio (A/F) is said to be 1:12.5 as the power air-fuel ratio, and 1:14.7 as the ideal air-fuel ratio.
Even with an air-fuel ratio meter attached, it is difficult to calculate accurately.
But it will serve as a guide.
When tuning FCR, you need to be aware of the season.
The air-fuel ratio is calculated by the ratio of the weight of gasoline and air.
The weight of the air changes depending on the temperature, so you need to change the tunings accordingly.
In the first place, the words "lean and rich" that are often used in FCR are expressed by comparing the fuel to the appropriate value or previous condition.
In summer, as the temperature rises, the air becomes lighter. Therefore, the fuel becomes richer.
In winter, the air becomes heavier as the temperature drops. So the fuel gets leaner.
That's what I said.

*Hiroshima Prefecture, Japan, where I live, has four seasons and the temperature changes drastically.

For FCR Beginners – Do I need to change the tunings between summer and winter?

In conclusion, either is fine.
I don't think you need to change the tunings throughout the year if you don't mind.
If you do not change the tunings throughout the year, tuning them in spring or autumn will allow you to cope with the heat of summer and the cold of winter with little change.
The reason I keep playing around with FCR is because I'm interested in FCR. It's for my own knowledge.
I have never touched TMR or CRS, but FCR is said to have a deep pocket, so it is difficult to set it up in a state where it cannot run unless you aim for it. I feel like it's easier to find the correct tuning for a carburetor that goes bad each season.
There is no need to change the tunings throughout the year.
Since it is a racing carburetor, I tried touching the AS, changing the number of clip stages on the JN,
Even if you change the MJ number by about 5, such as from 120 to 125, the feeling changes and it's very fun.
As for AS, if the motorcycle is easy to work on, you can adjust it without spending too much time.
Regarding the installation of racing caburetors such as FCR, each motorcycle owner has a different opinion. Please use the method according to each person's theme.
The reasons for installing FCR are:
① Because it's cool
② Performance improvement
③Because there are no substitutes
④I want to enjoy DIY
Such will be considered.
My original reason for operating FCR was ③, and now it is ④.
Should the FCR tunings be the same throughout the year? Do they do it four times each season?
Each person can choose whether to do it in three patterns: spring/autumn, summer, or winter.

FCR tuning – Considering the seasons of summer and winter when touching AS and PS – 2022-09-17【summary】

With AS, if the return is large, such as 2 turns, opening or tightening will have little effect. On the other hand, I feel that even a small change can make a big difference in the condition of the motorcycle when the speed is less than 1 revolution.
Adding 1 to 10 and adding 1 to 1 are completely different in terms of percentages.
Currently, I am doing test runs and adjusting the AS by opening and closing it until I feel it is good.
Everyone, please be careful about rain and typhoons and enjoy tuning up FCR.
See you again!

work photos

Although the chance of rain was over 50%, we did not encounter any rain at all.