FCR Tuning – Tuning that becomes worse due to jet changes is within the acceptable range of effects.

CBX1000-Engine FCR
This article can be read in about 18 minutes.

FCR Tuning – Tuning that becomes worse due to jet changes is within the acceptable range of effects.

I'll explain what I mean by "tolerating the deterioration of the engine".
If the slow jet is too large, it's hard to tell how effective the pilot screw is.
It's also hard to tell if the main jet is only moved one size smaller when the throttle is fully open.
If the acceleration pump is too effective, it's hard to tell if the tuning is correct.
It doesn't mean that the tuning result is correct, but that the range of influence of the tuning is correct.
Since the engine is not performing well as a result of tuning, we have been able to correctly find the range of influence.
It's just that the number is wrong.
If you know which jet to change and can see the change, then if you find the bad part in the rich direction,
and find the bad part in the lean direction, you can find the perfect best tuning for the range of influence of that jet. The jets in the tuning are interconnected, so it's not simple, but there's no doubt that it will result in very precise tuning.
I realized this while we were chatting.
If there is a change in the AB test, then you can be sure that what you are doing is correct.
Using strong words will always lead you to the right results.
If there is no change in an AB test, it means that you are doing the wrong work,
the carburetor or motorcycle is not in good condition,
the jet number is too far off,
or you have incorrectly confirmed the scope of the impact.
I will separate the above points and write them down with specific examples.
Let's get started!

If the jet is too big or too small, you won’t notice any change.

Specifically, if the slow jet is too large, the pilot screw will not work well and the engine will idle even when fully closed, so it is difficult to tell. If the slow jet is too small, the engine will not idle and the air-fuel ratio meter will show clearly abnormal values, so it is easy to tell. The pilot screw will not work either.
The main jet is hard to see any changes even if it is too lean.
Be careful, as the engine may burn out if it goes beyond being too lean.
The engine of the CBX1000 will not be damaged even if it is leaned up to 102.
The optimum range is probably 110-140, assuming that the main air jet is not touched.
If you select a main jet close to the optimum, you will notice a change in the acceleration feeling even at 1/2 to 3/4 throttle opening. I have never tried it in the richer direction above 140, so I do not know.
I suspect that the symptoms are similar to when the jet needle clip stage is set too rich.

If the accelerator pump is too effective, you won’t notice any change no matter what you do.

This symptom occurs when accelerating extremely quickly. In my case, I noticed it when accelerating extremely quickly with quick throttle. There is no change whether the jet is lean or rich.
The change in the air-fuel ratio gauge is constant.
When accelerating rapidly, the air-fuel ratio gauge shows 10.0 or less, and then the air-fuel ratio settles down to around 12.5. When the air-fuel ratio shows 10.0, there is an abnormal lack of acceleration, and then the engine accelerates sharply. Since the throttle was opened suddenly, I expected the air-fuel ratio gauge to show a lean value. When I turned off the acceleration pump, this strange symptom disappeared and the engine accelerated energetically.
It feels easier to ride lean and lacking in power than to have the acceleration pump make it rich and wait for acceleration.
Currently, the acceleration pump discharge timing has been adjusted so that the acceleration pump is not working too well. The acceleration pump can sometimes cause tuning to become invisible.

Others①- The instruments make it difficult to understand the tuning.

This may be a bit unusual, but sometimes maintenance factors can make it difficult to tune.

Instruments such as the air-fuel ratio meter may be out of sync.

The air-fuel ratio meter can tell you the difference between rich and lean, but it's questionable whether it's showing a reliable number.

Even if the air-fuel ratio meter shows 13.0, the actual number may be 12.5.

It's not showing a random number, so you can use it as a reference to see if it's lean or rich. The same goes for the compression gauge. The same instrument is used to measure compression, so it can only measure whether the pressure balance of each cylinder is off or not.

It's questionable whether the pressure is actually at a correct number, but it can tell you if it's not working properly.

The worst instrument to have out of sync is the multi-vacuum gauge.

If you don't calibrate it properly before starting work, you'll end up with a messed up synchronization even though you thought it was perfectly synchronized.

Others②-Motorcycle maintenance

Leaving aside factors such as the engine and ignition, this is an example of a human factor that can occur immediately after installing the FCR that is difficult to notice and can interfere with tuning.
The throttle valve is not fully open even when the throttle is fully open. This is something to be very careful about.
If you don't notice it, you will end up making endless, unnecessary jet changes. The symptoms are harder to understand than problems with low throttle opening. There are many cases where people have a preconceived notion that changing the main jet will improve the situation. If you are in a situation where you can check the opening and closing of the throttle valve, it is essential to get into the habit of checking whether all cylinders are fully open at the same time.
Conversely, this is a problem that makes it difficult to understand tuning at low throttle opening.
Fuel supply.
When using a paper filter, there was also a symptom of fuel supply not being able to keep up with the idling.
Also, fuel supply cannot be kept up with the angle of the fuel line or extreme air entrapment.
Most fuel filters are transparent. When symptoms such as running out of fuel appear,
it is essential to check whether fuel is reaching the fuel filter.
If there is not enough fuel being supplied to notice, the problem is easy to solve.
What's really bad is when the fuel supply is just right, even if it's a subtle feeling.
If you don't notice it, you'll never notice it, even if you change the slow jet or turn the pilot screw.
In fact, because it's an FCR, it will stop if you idle for too long.
I ran at high RPMs for a long time and it started to run out of gas.
The fuel supply is not in time, so I'll change the gas cock.
If you don't notice it, the symptoms will not improve.
At least in the case of my CBX1000, the symptoms appeared when I was using a paper fuel filter.
Since changing to a mesh fuel filter, I haven't had any trouble with the fuel supply.
There are endless things to say, such as ignition timing and secondary air intake from the manifold, but
it might be fun to move the ignition timing a little at a time and check which position is appropriate.
I don't know how to measure whether it's appropriate for the engine, but
if you advance the ignition timing with AS Wotani SP2...
[0] → [1] I re-tuned the overall tuning to a richer number.
[0] → [9] I didn't fine-tune the tuning because I couldn't imagine it getting any better.

FCR for beginners: Adjust until you can see the changes

Most FCR beginners have their FCR installed at a custom shop and continue riding their motorcycle as is. Many people then try tuning the FCR.
If you think about it calmly and normally, there is no way that a carburetor can be tuned better just by touching it a little.
If you are serious about tuning, adjust it until there is a change.
As a premise, you should not know whether the current FCR tuning is good or bad.
You should be able to ride without feeling any particular stress.
You can access it from the air screw and pilot screw.
For the air screw, ask the shop that installed it how it was tuned, if possible. Is the return of the air screw uniform? Or is it different for each cylinder?
This is the problem. If it seems to be different for each cylinder, you can ask the motorcycle shop that installed it how it was done. If you are unsure, it is fine to make it uniform. If you are adjusting each cylinder, use a digital tachometer or judge by sound. I basically make it uniform on my CBX1000.
When I measured it with a digital tachometer, I did not feel any significant difference.
It depends on the tuner's opinion, but you may adjust the air screw for each cylinder.
I work on carburetors frequently, so I only adjust each cylinder occasionally, considering the time and cost.
As for the pilot screw, I have no choice but to make it uniform for my CBX1000.
I haven't been able to find a way to adjust it for each cylinder.
The pilot screw is too much work to touch on the CBX1000 without a pilot screw adjustment tool. What's more, if you have an air-fuel ratio meter, the adjustment will be completed quickly.
Once you start adjusting the air screw and pilot screw, you can also try touching the jet needle clip. There are no additional jets to purchase, and you can enjoy the changes.
At least in the areas where you can feel a change, you can be sure to settle the tuning in a positive direction.

FCR Tuning – Tuning that becomes worse due to jet changes is within the acceptable range of effects.【summary】

If you think about it, if something starts to run badly, it means that the extent of the impact is clearly known.
This blog post has described what to do if tuning does not produce the expected changes.
Tuning is an easy task if what you expect happens exactly as you expect.
If you have just started tuning your FCR, you probably won't even be able to predict how it will change.
The result of changing the jet and not making a difference is information you can obtain.
You have to keep changing the settings until you see a change.
Tuning is repeated AB testing. You won't know if the current situation is good or bad without comparing.
So that was the story of how it's okay for tuning to result in something worse as a temporary result.
See you again!

CBX1000 Photo Gallery

Here is a photo from a previous post showing the rounded naked style with fender lines. I like this look the most.
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