FCR-tuning-MJ and JN influence-22/07/08

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FCR-tuning-MJ and JN influence-22/07/08

In the previous blog, when I started suddenly, there was a bump around 1/2 throttle opening,
I was a little worried.
The cause was the combination of the MJ main jet and JN slow jet.
The reason for the judgment was that if the MJ was extremely lowered, it would not go away, but there would be a change.
It is less likely to cause bumps, the air-fuel ratio does not reach 10.0, and the accelerator is so fast that it can be called waiting to open.
Symptoms that were slow to catch up have also improved.
The reason why there was not much change even when changing the straight diameter of JN was that
I think this is because there is only a change of about 0.01mm in the first position.
On the other hand, MJ changes by 0.02mm from 123 to 125.
I think that changing from 125 to 135 will change about 0.1mm.
I think the number for each count is the thickness or diameter.
It may be possible to actually measure it, but I cannot measure it accurately with the measuring equipment I have.
In the current CBX
Compared to JN90-FTS, MJ seems to be at its limit around 123.
A larger MJ or 132 felt better, so while using the larger MJ,
I would like to eliminate the bumps that occur when the throttle is opened suddenly around 1/2.
As a candidate to try,
Changing taper angle

If you increase the clip taper angle with the same straight diameter, it seems that if you raise it about 3 steps, you will get the same straight diameter with a low opening. On the other hand, if you reduce the taper angle and the straight diameter is the same, lowering the clip by 3 steps seems to be just right. If it's from 4th tier, it's 7th tier and 1st tier.
This is knowledge that I gained from YouTube, the internet, and other people.
Anyway, if you change the taper angle, with the same straight diameter and the same number of clip stages,
It seems that the other tunings are not the same.
It might be better not to think too much about it, wondering if it will become a different type of JN.
If you want to change at least 1/2 of the throttle opening, changing the taper angle is essential.
Here's how things are going. However, since I only have JN with the same taper angle,
I have no choice but to purchase a new one. Tomorrow, I'll go to the motorcycle shop.
Let's go.

Plan for next tuning

Next time, with this tuning,
Now that I know the points of interest, I will work based on them.
In short, MJ was made too large than necessary.
The tuning is
Set SJ to 55 or 52
Make SJ 90FTS
Open AS as wide as possible
MJ 123 or 125
I'll make it.
When the accelerator pump starts to work, the point where it opens rapidly and becomes thin is around 3/4, so at the throttle opening of 5/8.
I make adjustments in advance to make sure it works, and plan out the tunings in advance.
Even if you order JN with a changed taper angle, it will take some time to arrive, so
Until then, I'll try various things with the jets I have.

FCR – For Beginners – Jet Accessibility

I will write about FCR's jets in order of ease of access.
The easier it is to access, the more frequently you need to touch it.
As an exception, it is best to touch the PS with the engine running.
The easiest part to touch during tuning is the stop screw. Used for adjusting idling.
Adjust the opening to fully close. This is the initial value when the throttle is fully closed.
The second is the AS air screw or PS pilot screw.
And for AS, it is easy to see the changes after touching the screw.
The third part that is easy to touch is the JN jet needle.
Although it involves work such as lowering the tank and removing bolts, there is no need to spill fuel.
The fourth is the MJ main jet.
The fuel will drop out, but there is a dedicated exchange port, so if you are concerned about it, just change it.
The fifth and final one is the SJ slow jet.
If it's a Maruti FCR, it's difficult to replace it without removing and removing the carburetor.
Although it is possible to replace it without forcing it on and off, we do not recommend it as it may cause problems such as fuel leakage. I think it would be best to operate FCR with the policy of not replacing SJ excessively once you have decided on it.

FCR-tuning-MJ and JN influence-22/07/08【summary】

In this case of sudden opening with 1/2 throttle opening, I didn't buy a manual,
If I hadn't installed an air-fuel ratio meter, I might not have noticed it clearly.
Lean and rich combinations of MJ and JN may not be solved without changing the taper angle.
I looked at the manual and found that by changing the taper angle, the air-fuel ratio per 1/2 throttle opening is
It changes a lot. There's no point in getting too excited, so once you've made your preparations,
I'll try replacing the jets and clips until I'm satisfied.
I hope everyone has a fun FCR life.
See you again!

*MJ and JN part numbers and work photos are posted at the bottom.

CBX FCR-MJ replacement work photo

I'm concerned about the tension of the throttle wire, so I try my best not to remove the wire while working.
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