FCR tuning – Change and synchronize SJ and MJ – 2022-09-27

FCR tuning – Change and synchronize SJ and MJ – 2022-09-27

I went for a long distance test run the other day. So I changed the jet as feedback.
The current tunings are as follows

SJ-42
PS-2.20 minutes return
AS-2.10 minutes return
JN-90FXM#2
MJ-128
Uotani ignition timing [1]
Acceleration pump diaphragm is KLX250
Discharge timing is 10mm

The change is
SJ-38
AS-0.45 minute return
MJ-125

It becomes.
First of all, regarding the MJ main jet, I drove on the expressway the other day and it had a very good feeling.
When I look at the air-fuel ratio meter, I wonder if it would be better if I made it even a little leaner.
It was showing movement. So it may not make much sense, but
MJ was changed by one step from 128 to 125. It may not really mean much, but
This is the season when fuel becomes richer as we approach winter. There is no problem even if you shake it a little thin.

Next is the SJ slow jet.
Once you decide on SJ, there is almost no need to change it throughout the year. The recent trend for me is to go richer, but I haven't tried the smaller SJ recently, so I decided to try it this time.
The main reason was that the AS air screw was close to its limit and I wanted to resolve it.
The initial price sold at BITO is SJ40, but I will try changing it for the time being.

About AS air screw.
Since I changed the SJ, I have returned the engine to a point where it seems to start well and I am testing it.
I don't know much about PS, but I'll try PS and AS while checking the startability.
For now, I won't be able to talk until the engine starts, so I'm keeping a close eye on it.

Carburetor synchronization and throttle wire tension

If you change the SJ, touch the idle stop screw, or install or remove the carb,
Be sure to check the return strength and play of the throttle wire.
Since it is a two-pronged throttle wire, check that the throttle valve starts rising at the same moment. And since the FCR is a calibrated opening/closing type, the play can be adjusted to the bare minimum. Personally, I don't like the free play of 0mm. I have synchronized the carburetor many times. It has become possible to finish the job in less time, but recently it has become troublesome to attach and detach the tank and prepare tools.
It's good that I'm less nervous about what I'll do if I fail.
However, I will be careful not to make the mistakes I make because I am used to it.

I use 6 vacuum gauges to synchronize. Purchased two 4-way vacuum gauges.
There are 6 specifications. The remaining two were resold at auction. It seems that some people want it as a single item. Vacuum gauge made by Daytona.
The negative pressure outlet nipple does not have an outlet on the cylinder head side, so a negative pressure outlet nipple is added separately to the manifold.

FCR jet change work

First, turn the carb over and drain the gasoline from the air vent.
I put it in a lightweight cup and transfer it to a sub tank for synchronization, but it's quite a lot.
If possible, I don't want to remove the throttle wire even if I install and remove the FCR.
In the case of CBX1000, it is impossible to change the SJ slow jet without removing the float chamber, so you can quickly install and remove the FCR without worrying. If you do not remove the chamber in a location where it is easy to work, the chamber gasket may not be installed properly and gasoline may leak during installation.
If the chamber gasket is deformed, dry it thoroughly to make it easier to install.
If it is difficult to install even after drying, please discard it and use a new chamber packing.

Throttle wire adjustment

Please use both the return and pull throttle wires. It is also stated in the FCR tuning manual. In rare cases, there are motorcycles that are only equipped with a pull. You won't be able to adjust the throttle strength or play, or rather the width will become narrower. It is very dangerous if the return does not work.
My CBX1000's FCR is an older model, so the throttle wire is split into two. It looks like two triple FCRs are installed. There are also two throttle stop screws. It seems a little difficult to adjust the idling and throttle wire tension.
Adjust the idling stop screw to make sure that the opening of the throttle is uniform between throttle valves 123 and 456. When the throttle is fully open, the tension of the accelerator wire is adjusted to ensure uniformity between throttle valves 123 and 456. It was quite difficult to get used to. It took me a long time to realize that something was wrong and to find the flaw. If this area is not properly aligned before synchronization,
No matter how hard you try to synchronize, no matter how many times you try the tunings, something seems strange. Nowadays, CBX1000 kits with two triple FCR units are no longer on sale, so this information may not be in demand. Please use this as a reference for maintenance of other motorcycles that use two-pronged throttle wires.

For FCR beginners – Adjusting the throttle wire after installing and removing the carburetor

My CBX1000 has two wires as shown above, but even with an FCR that has one pull and one return wire, there are certain items that must be checked after removing the throttle wire. The point is whether the FCR throttle is completely open when the throttle is fully opened. Please note that the throttle valve may not open fully depending on the tension of the throttle wire and the position where the tycoon is installed.
Also, FCR is a carburetor that controls the throttle yourself.
For me, it feels more lively to play as little as possible, which is what I prefer.
The position of the idling stop screw will also change, so you will need to check the engine speed again. It's easy to adjust, so it might be fun to try adjusting the throttle wire even if you haven't installed or removed it. This can be done by adjusting the throttle side. First, relax the pull and return to the limit. This is the direction in which the wire comes off. Adjust the strength on the return side, then adjust the play on the pull side. When you touch the return button, a change will appear in the pull, so you can adjust it to the ideal position by repeating it two or three times.
The spanners used are 8 and 10.
I can definitely say I'm glad I did it.
The difficulty level is low, so if you are interested, please give it a try.

FCR tuning – Change and synchronize SJ and MJ – 2022-09-27【summary】

This time I didn't really set it up, but I felt like there was a lot of work involved in putting it on and taking it off.
Changing SJ will reset the screw tunings, so
I will continue to look for good things about PS and AS.
In addition, the adjustment of the idling height is delicate, so you will need to make adjustments during a test drive.
I felt happy when I synchronized the caburetor for the first time in a while.
Until a few days ago, I was messing around with the idling stop screw.
It remained as it was.
In the past, the SJ38's throttle opening has ranged from fully closed to about 1/4, so I'm thinking of using this as a reference and checking the time from tomorrow onwards so I can drive on Saturdays and Sundays.
I hope you all have a wonderful FCR life.
See you again!