FCR settings – The symptoms of being too rich while riding are easy to recognize if you pay attention.

FCR settings – The symptoms of being too rich while riding are easy to recognize if you pay attention.

This is a story about a time when I couldn't figure out the cause and was troubled for a long time.
The accelerator pump was too rich, and when the throttle was opened quickly, the air-fuel ratio meter indicated 10 for a few seconds.
After that, the bike would accelerate energetically.
As I'm writing this now, I know the cause and have already addressed it.
However, I was very troubled when I didn't know the cause.
The cause was replacing the normal throttle with a quick-turn throttle.
As the title suggests, if I had known clearly about the symptoms of being too rich, I would have noticed it immediately.
No one will teach you this.
You have to notice it yourself.
When the throttle was opened quickly, the air-fuel ratio meter showed 10.
I thought that was the cause.
When the throttle is opened quickly, the airflow speed increases, so it should become lean.
Suddenly showing 10 was a sign.
I had a preconceived notion that FCRs had such characteristics.
What decisively made me realize the issue was that the symptoms described above did not occur when I turned off the accelerator pump and rode.
As a solution, I reviewed the overall tuning and adjusted the discharge timing of the accelerator pump to start from a throttle opening of more than 1/2 and slightly shortened the total discharge amount (time) of the accelerator pump. There is still more work to be done on the accelerator pump.
Being aware of the symptoms of being too rich while riding helps in tuning the FCR.
When I tune the FCR, I prioritize observing the air-fuel ratio during acceleration.
When there are symptoms of being too rich during acceleration, there will be a moment when it accelerates with an appropriate air-fuel ratio within a few seconds. If it's too rich at partial throttle, the acceleration will feel sluggish.
This blog post will focus on the symptoms of being too rich, not just rich.
So let's get started!

The air-fuel ratio should always be appropriate when the throttle is fully closed and during idling.

As a premise, I'll be writing about riding, but first, let me address too rich conditions during idling.
A too rich condition during idling can be somewhat misleading, or sometimes even beneficial.
If the engine can start and maintain idling, then that tuning is appropriate.
It's easy to check the air-fuel ratio during idling. As long as the air-fuel ratio is around 12.5-13.0,
the engine will start, and idling can be maintained.
However, there's a small pitfall: if the slow jet is too large, the engine can start and idle even with the pilot screw fully closed.
An appropriate combination of slow jet size and straight diameter allows the engine to start and idle with the pilot screw set between 0.30 to 1.30 turns back.
This is different from being too rich while riding, but remember that if the pilot screw has no effect when the throttle is fully closed, the combination of the slow jet size and straight diameter is too rich.
Generally, this means you'll need to change the slow jet to a leaner size.
If there is no change with pilot screw adjustments, I make the slow jet size leaner.

Being aware of a too rich condition while riding makes tuning easier.

If you have an air-fuel ratio meter and it clearly shows a value of 10.0, that indicates a too rich condition. It feels like the engine is misfiring or struggling to lean out the fuel mixture. If there’s a sudden drop in power, it’s a sign of being too rich.
Try reverting to the previous jet size and retune from there. Additionally, consider that debris might have entered when changing jets, or the accelerator pump might be too rich.
There is a specific way to experience a too rich condition. By setting the clip position three steps richer than the current setting, you will immediately notice the symptoms.

Determining a too lean condition while riding is difficult.

Determining a too lean condition while riding is difficult. You may just feel a lack of power or acceleration, but the bike will still run normally, making it hard to identify the symptoms.
When the mixture is lean, the changes are noticeable.
Sometimes, you might have the illusion that the bike's performance has improved after adjusting the jets.
However, it is not ideal when the engine runs at high RPMs, including engine braking, in a too lean condition.
A too lean condition is usually still rideable.
There is a risk that the engine might seize at the moment of excessive RPMs.
Nevertheless, if the ignition timing is not advanced, the chance of engine damage is low.
A lack of power or poor throttle response might indicate a too lean condition.
Please keep this in mind.

If black smoke is coming from the exhaust due to being too rich

While it depends on the extent, it's not normal for the exhaust to emit black smoke frequently if the tuning is too rich. Please review the settings. Black smoke may not occur all the time but can appear intermittently.

You might see black smoke more frequently when you open or close the throttle. For instance, black smoke can occur when the setting is too rich, and fuel is supplied from the accelerator pump.

In such cases, you might still be able to ride the bike without much stress, but the fuel economy will be extremely poor. Black smoke from the exhaust indicates incomplete combustion of the gasoline.

FCR settings – The symptoms of being too rich while riding are easy to recognize if you pay attention.【summary】

When tuning FCR carburetors, everyone is likely to be mindful of whether the mixture is lean or rich. A "popping" sensation during riding is a symptom of being too rich. It's a recognizable symptom if you know what to look for.

For those who are about to challenge FCR tuning, be conscious of this and try test riding with this in mind. If you don’t have an air-fuel ratio gauge, it might be a good idea to start tuning from a point that is too rich. If you don’t feel the popping sensation and haven’t yet changed the jets to leaner settings, you can consider it acceptable. At that point, you can reasonably assume that the tuning is roughly appropriate.

The idea is not to find the perfect tuning but to eliminate the problematic areas. If you have an air-fuel ratio gauge, it will clearly indicate if the mixture is dangerously lean.

This blog post discussed being too rich while riding. See you again!

CBX1000 Photo Gallery

Here are some photos from previous posts showing the skeleton of the CBX1000.