FCR-6-synchronization-balanced pipe

HONDA CBX-FCR negative pressure balance pipe FCR
This article can be read in about 14 minutes.

FCR-6-synchronization-balanced pipe

This time we are talking about balance pipes rather than synchronization.
The local mechanic who assembled the CBX engine
“Make sure you're in tune. ”
is often said.
“There are six of them, so how do you synchronize them? ”
There was a time when I thought that.
By the way, the mechanic mentioned above is a god-like person who repaired the engine of my CBX for free. I don't want to just ask for help, so if I touch something myself, I report it, and I try to bring in midyear and year-end gifts.
Let's go back to the tuning gauge.
There are also items available for FCR that measure negative pressure by applying it to a funnel. A link will open to Amazon.
synchro tester

I think this name is due to trademark issues.
I bought two 4-gauge vacuum gauges and modified them to use a 6-gauge version.
I always calibrate the needle before using it. The link is a past article. I have written a rough guide on how to do it. Includes photos and videos.。

FCR synchronization and 6-series vacuum gauge
Calibration and adjustment of vacuum gauge. Align the synchronization of CBX with 6 vacuum gauges. If you are using a 4-way vacuum gauge, you can easily find out how much the difference is by replacing the numbers 1 and 2 that you normally use.
The FCR itself also requires processing. You will need to add a nipple to take out the negative pressure. A standard carburetor with a throttle wire is equipped with a special spigot when purchased. In my CBX's FCR, negative pressure extraction nipples were attached to cylinders No. 3 and No. 6 from the beginning, and they were covered with rubber caps. We are currently using vacuum gauges by attaching negative pressure nipples to Nos. 1, 2, 4, and 5, and extracting negative pressure from them. It would have been possible to install a cap, but due to the engine cycle, the corresponding spigot I read somewhere that connecting them together will increase the stability of the negative pressure, so it's a pain to attach a cap, and it's better to do something that will improve performance, so I'm currently using the balance pipe specification. We now have. I also have a blind cap on hand, but I haven't tried any changes. I'll try it when I have time. I didn't try it because I thought the result would be that I couldn't tell the difference. There are other important things too. I'll write about it in the next section. The other day, when I replaced the accelerator pump's diaphragm, I took some photos, so I'll post them as well.

Be careful with the balance pipe. CBX ignition timing

There are three ignition coils in the CBX.
Why 3 cylinders even though it has 6 cylinders?
Light 1 and 6 at the same time. Light 2 and 5 at the same time. This is because No. 3 and No. 4 are lit at the same time.
If you write what you want to write early, the balance pipe connections are number 1 and number 6. No. 2 and No. 5. Connect No. 3 and No. 4.
The engine firing order is
The order is 1-5-3-6-2-4.
From this point on, I'll include some technical details about the engine, so I'll just write about it briefly.
When No. 1 is compressing and igniting, the cylinder with the farthest ignition timing is No. 6.
No. 1 and No. 6 pistons are ignited at the same time, but the No. 6 piston is in a state where it does not affect the ignition.
The balance pipe connects the negative pressure outlet nipple of the pair of cylinders including the piston.
The purpose of this connection is to stabilize negative pressure. If it is a 4 cylinder DOHC engine,
Numbers 1 and 4, and numbers 2 and 3 are paired. The firing order is 1st, 3rd, 4th, 2nd.
*The above order may differ depending on the vehicle.
There are four reasons why I use a balance pipe.
①It is troublesome to put on the blind cap
② The blind cap is small and there is a high possibility of losing it.
③There seems to be no disadvantages.
④I want to run it if it improves performance
None of the above (1), (2), (3), and (4) are reliable and can be solved by taking measures, and I have not verified them.
However, for people like me who often install vacuum gauges on their motorcycles, the balance pipe specification slightly improves maintainability.
Easier to put on and take off than a rubber cap.
As for the nipple, it is easy to check whether it is attached securely as a blind.
Since the balance pipe is quite long, it is less likely to be lost compared to a blind cap.
There may not be much of a performance advantage to using a balanced pipe, but if you write it down like this, it seems like there are some maintenance reasons.
There are other things I'm concerned about, and I'm consciously checking them.
The balance pipe was broken and air leaked from the negative pressure outlet nipple.
We visually check for breaks in the balance pipe.
Regarding air leakage from the nipple, spray some parts cleaner and see if the rotation speed changes.
I'm looking forward to seeing it. Since racers and the like do not have negative pressure outlet nipples installed on all cylinders, I am wondering if there is a need for a negative pressure outlet nipple, if a synchro tester will suffice, and if the synchronization accuracy does not need to be that high. I'm curious as to why.

FCR-balance pipe photo

The photo may be hard to see, but you should be able to get an idea of it.
Please use your imagination to cover it.

FCR-For Beginners-Synchronization

How much synchronization should I achieve? I'm sure everyone is worried.
There is only one answer. It's perfect.
But it's difficult.
It is fine if the engine is not idling too high or the rotation speed is difficult to drop when the engine gets hot or when the throttle is released.
If the idling is extremely high, the deviation is large.
If you have a forced open/close type carburetor, measure the height of the throttle valve with a ruler,
Another method is to put a cotter pin or similar object between the throttle valves so that they release at the same time.
Also, riding a motorcycle can be dangerous if the engine speed does not drop when you release the throttle.
Please complete the synchronization process quickly or use a fan. Your engine's temperature will be higher than you think.
If you are planning to buy a tool for FCR tuning, you may have budget constraints, but it is better to choose one based on the fact that it will shorten your work time. Or please add more.
The idling may become too high while driving, so it is better to check the location and feel of the stop screw in advance.
It is difficult to get everything perfect due to complex factors such as the subtle adjustment of the throttle and the condition of the engine.
When looking at it with a vacuum gauge, it may be a good idea to decide that if it is less than 5KPA by one scale, it will be acceptable. The answer is exactly the same.

I also watch and synchronize the moment the throttle valve opens and the moment the throttle valve fully opens. This is a particular weakness of FCR, which uses a two-pronged throttle wire.
Finally, there are two stock screws, so slightly move one of them to find the best place for the engine to slow down. The reason is that there are individual differences in the way the throttle is raised, and the tension of the throttle wire is also different, so it is assumed that moving objects cannot be perfectly matched.
It is unclear whether it is correct to use the stop screw to balance the books at the end.
It's not good when it comes to making ends meet, but as long as the throttle valves are in the same fully open position, I think things are good for now.

FCR-6-synchronization-balanced pipe【summary】

The idea of a balance pipe is an old idea, and if you think about it in modern times, it may or may not be something you should do.
In my case, the method is a bit wrong, and I have three balance pipes, but they are all different lengths.
It is used only to connect the spigot. Actually, all lengths should be the same. Currently, we have only secured the shortest length.
I hope you have a good FCR life!
See you again!
Copied title and URL