FCR tuning-PS pilot screw changes22/07/25

CBX and Carburetor pilot screw adjustment tool FCR
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FCR tuning-PS pilot screw changes22/07/25

After doing various work from the other day, I found out the scope of the PS pilot screw's responsibility! Because I feel like
I went for a test drive to find out which air-fuel ratio is best while tuning the PS.

Regarding the air-fuel ratio for each throttle opening
・Around 15 when fully closed
・1/16-1/8 around 12.5
This is the situation.
When fully closed and idling
①Is around 14 good?
②Is around 12.5 good?
That's the idea.
It's an easy job because you can control it to some extent just by touching the PS and looking at the air-fuel ratio meter.
As for my preference, I like ② as it has a milder feel.
When I look at other people's stories and the opinions of my predecessors on the web, I wonder if it's ①.
By the way, retuning the screw
AS-1.Go back 10 minutes
PS-3. Go back 15 minutes.
It's SJ-40.
Since SJ is at the very limit, we need to consider it a little.
When replacing the SJ, the proper position of the screw changes greatly.
It doesn't control only that, so as long as it doesn't go beyond the scope of adjustment,
I will touch on it with the current SJ-40.

What I learned after changing SJ

By modifying the Carburetor Pilot Screw Adjusting Tool so that it can be used while the engine is running, I was able to understand the range of influence of the PS.
It might be more accurate to say that I noticed it. There are holes called the idle port and slow port, and the job of the PS pilot screw is to control the air-fuel mixture that passes through those holes.
The reason why SJ was made extremely small may be the reason why we have come to understand the scope of SJ's responsibility.
Until now,
I had selected SJ so that it would have the same depth at idling and at a throttle opening of about 1/16, so
I didn't notice the difference between an idle port and a slow port.
It's all in my own way, but once you understand it, it's a lot of fun.
Next, without changing the SJ too much, touch the screw with [42] or [45] and see what happens.

Reference photo

I go deep into the mountains with the Carburetor Pilot Screw Adjusting Tool and touch both the AS and PS screws.
If you do it at home, there is a high possibility that you will get complaints and it will make your life difficult.
The Carburetor Pilot Screw Adjusting Tool is sanded with a sander to eliminate interference with the engine and allow it to be used while idling. I borrowed it from a motorcycle shop and tried out which Carburetor Pilot Screw Adjusting Tool was better.
I tried about 3 tools, but I couldn't find the Carburetor Pilot Screw Adjusting Tool that fit me perfectly.

For FCR beginners – Preparation of packings

It is best to prepare tools and gaskets in advance for the parts you plan to touch.
Please purchase as little as possible.
For beginners, the basic idea is to do some research before trying it out.
Tools and gaskets are often not readily available. Please obtain it in advance before starting work. If the gasket becomes unusable during work, the motorcycle may become unable to run and there is nothing that can be done.
It also needs to be assembled in order to be disassembled.
It would be very bad if it became impossible to drive if it involves moving the location.
What kind of gaskets should you have in advance?
・Drain bolt (substitute items available at home centers, etc.)
・Chamber packing
・Jet needle clip (substitute items available at home centers, etc.)
・O-ring if the fuel line is quick release
In particular, there are many cases where the chamber gasket gets damaged when replacing the SJ.
If the shape of the chamber gasket is swollen and large, try wiping off the gasoline and drying it. It may return to its proper shape.
In most cases, the preparations listed above can be resolved without any problems if prepared in advance.
Please be aware of this.

FCR tuning-PS pilot screw changes22/07/25【summary】

Since the beginning of July, I think I have been able to do more things, or rather, my level of understanding of the 1st stage FCR has increased.
The reason for this is that the JN jet needle has a sharp cut and taper, and the Carburetor Pilot Screw Adjusting Tool for CBX is on hand.
I hope everyone has a fun FCR life.
See you again!
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