FCR Tuning – Jet Search Order from Initial Tuning

This article can be read in about 18 minutes.

FCR Tuning – Jet Search Order from Initial Tuning

I received an email asking for advice about the FCR of a CBX1000.
I'm an amateur, but I try to tune it diligently in my own way and send out information.
I don't work on motorcycles for business.
I'm very happy when I get reactions from the web.
I'm currently in the process of tuning the FCR.
What I've written in the past may differ from what I'm writing now.
This time, I'll write about the order in which to tune the FCR from the factory.
I'll write this assuming that an air-fuel ratio meter is already installed.
Attaching an air-fuel ratio meter is a bit of a hassle.
If you do it at the same time as you first install the FCR, there will be less time lost.
The premise is that you first ask a motorcycle shop or custom shop to install the FCR.
All you have to do is ask them at the same time.
The air-fuel ratio sensor needs to be welded to the muffler, so it's a bit difficult for individual DIYers.
You can remove the muffler yourself and ask a factory with the equipment to do it.
If a motorcycle shop is willing to do welding, it's better to ask them to do it.
I will write about this as much as I can within a day or so after I bought my brand new FCR.
So let's get started!

The initial tuning is set to the factory default setting.

There is a high chance that the engine will start with the FCR installed in its factory condition.
Synchronization will not be perfect, but we will proceed under the assumption that it is at a level that is not noticeable.
The oil level is also assumed to be appropriate.
Check the jet numbers and leave the screws at 1.0 or the factory default position. Be sure to take careful notes.
If you are not sure how to take notes, there is a template for taking notes in the tuning manual. Tuning is a repeated A/B test, so a history is essential.

① Start the engine while watching the air-fuel ratio gauge and adjust the slow jet and pilot screw.

While watching the air-fuel ratio meter, turn the PS open or closed in 15-minute increments.

At this point, since the engine is cold, the air-fuel ratio is about 13.5.

If you have an air-fuel ratio meter, when tuning is not going well, you can see at a glance which way to turn the jet, rich or lean.

If you don't have an air-fuel ratio meter, you may only know whether it's good or bad.

Then, as the engine starts, the air-fuel ratio gradually settles down. Adjust the pilot screw until the air-fuel ratio meter indicates about 12.8. If the slow jet is the right number, moving it about 15 minutes with the hands of the clock will make a difference when the throttle is fully closed. If the pilot screw seems to be ineffective,

change the number of the slow jet. The pilot screw is closed with the hands of the clock

If it is outside the range of about 30 minutes to 2.30 minutes back, you can change the slow jet.

You may want to turn the pilot screw to its limit.

If there is no room in the screw, you will need to change the slow jet.

② Adjust the air screw only when starting

Although it's not at the level of a test run,
adjust the air screw while checking that the engine can start transmitting smoothly.
If the FCR is initially tuned and meets step ①, you will generally be able to find the air screw return without any problems.
If the air screw is too tight, the engine will stall.
If it's too open, the engine will feel sparse and without any power.
If you find that it's sparse and without any power, then it's too lean,
but once you find the air screw return that allows the engine to start transmitting properly, that is roughly the best air screw return position. There is no problem with adjusting the air screw even richer from there.
Do as you like.

③ Setting the jet needle clip stage

Move the clip step from lean to rich in sequence.
In terms of throttle opening, this should be up to about 1/2.
Ride while observing the legal speed limit in town.
Ultimately, it is better to find a clip step that you cannot drive at.
If you can drive without stress, it may not be a problem if the clip is off by about two steps.
Tune while watching the air-fuel ratio gauge.
It is good that the clip is between 12.0 and 13.0 when there is a sense of acceleration. If it suddenly shows a rich state for an instant, this is due to the acceleration pump timing being too early.
There is no need to immediately adjust it to off, etc.
If you are accelerating, the effect of the acceleration pump will settle down quickly.
Decide on a good clip step.
If you are already at the appropriate clip step, you can also determine an inappropriate clip step.
Tuning by looking only at the values ​​on the air-fuel ratio gauge may result in a lean state and tuning with a low sense of acceleration.
Decide on the clip step based on how you feel when driving.
There's no problem leaving the straight diameter and taper at the initial tuning.
Change them when you are satisfied with the tuning.
If you can't decide on anything, change the jet needle with a different cut-off.
If the cut-off does not work, changing the taper will allow you to select a jet with a two-stage cut-off.

④Selection of main jet

It is a good idea to purchase a set of main jets in advance.
Try changing the main jet number in increments of about 5.
Decide based on the acceleration feeling at about 1/2 to 3/4 throttle opening.
It is largely determined by the combination of the jet needle's straight diameter and the main jet.
The manual says that the taper angle is one of the tuning factors,
but changing the taper angle will result in a different tuning, so when changing the taper angle,
it is better to do it with the mindset of starting over from the beginning when you are finalizing the tuning of the FCR.
The combination of the main jet with the straight diameter also affects the full opening of the main jet,
so change it when you are finalizing the tuning.
Once you are satisfied with the acceleration feeling at about 1/2 to 3/4 throttle opening,
the main jet at full throttle should not feel too far off.

⑤ Adjust the carburetor synchronization until you are satisfied.

At this point, try synchronizing the carbs until you are satisfied.
After steps ① to ④, you should be able to drive with less stress.
If you don't feel any negative effects, that's because the tuning is correct.
If you also check the air screw and pilot screw adjustments again, you should be able to tune with greater precision than you did the first time.
Unless you can't help but wonder if there is a great tuning out there, it's no problem to stop tuning at this point.

⑥Adjust the accelerator pump before getting into tuning

The accelerator pump needs to be adjusted before delving into tuning.
Or it is better to tune with the accelerator pump turned off.
The suitability of the accelerator pump will vary depending on the throttle operation of each rider.
Everyone has their own preferences when it comes to adjusting jets.
The accelerator pump is a very personal element.
In extreme cases, there are tunings that do not use an accelerator pump at all.
However, FCRs are specially equipped with an accelerator pump function.
It is normal to want to make effective use of it.
The accelerator pump is best adjusted while checking the air-fuel ratio meter.
Adjustment is made by the width of the plate on the reference carburetor and the size of the diaphragm for the pump.
Tuning is done based on the idea of ​​how much throttle opening the engine should discharge for how many seconds.
Complex tuning is not possible. It is an FCR's flavoring element.

⑦Perfect tuning

While test driving while staring at the air-fuel ratio meter, please refine the straight diameter of the jet needle, the number of clip stages, and the main jet. The low throttle opening is determined by the combination of the slow jet and the straight diameter of the jet needle. Up to this point, the tuning should not be off. You can limit the change in the straight diameter to about the second largest. If you change it any more, you will need to change the slow jet. The jet selection may not be appropriate from the beginning. The selection of the main jet is also a balance with the jet needle.
If you can accelerate comfortably from 1/2 throttle opening to full throttle, the main jet is appropriate.
Refining the tuning also includes adjusting the size of the throttle, the play of the wire, the return strength, and the ignition timing. It may not be directly related to the FCR, but if you change it, it may be an item that requires retuning the FCR. Refining the answer is not easy to find. Repeat it over and over again until you are satisfied. All you have to do is repeat the test drive and change the jet.

For FCR beginners – Spend money on jets, tools, and repair parts

If a beginner attempts to tune an FCR, they probably won't have the tools, jets, or repair parts.
Depending on how far you want to tune, you won't be able to move forward with tuning unless you purchase the necessary equipment.
We're not saying you should buy jets and tools without thinking about it.
However, if you need them, you should purchase them straight away.
Veteran FCR tuning experts have plenty of jets and tools.
Everyone bought up tools and jets when they were beginners.

FCR Tuning – Jet Search Order from Initial Tuning【summary】

When I write about it, I feel like the tuning I do on a regular basis isn't that difficult.
Before I started writing this post, I thought it would be a bit rough and not very detailed.
Now that I've written about the tuning I do on a regular basis, I feel like I'm not doing anything complicated.
I think the most important thing is the number of times you tune.
I predict how much of a change there will be when I change the jet, and then I change the jet.
When I first started tuning FCRs, I didn't think about where and how much of a change there would be when I changed the jet. I had no idea how much of a change changing one place would have on other parts in a complex way. Nowadays, it's often the case that you don't know how much of a change there will be in advance, but
I realized that tuning repeatedly improves the accuracy of your tuning.
So I wrote this blog in the hope that it will be helpful to riders who are thinking about starting to tune their FCRs.
Nowadays, you can easily buy jet needles on Yahoo Shopping and other sites. If you have any questions about FCRs, please try searching for the size.
I hope you have a good FCR life!
See you again!

CBX1000 Photo Gallery

This is a photo of me when I went to pick up the Honda genuine parts I ordered from a motorcycle shop. We store CBX1000s in our rental garage.
Copied title and URL