I am the owner of a Honda motorcycle [CBX1000] who lives in Hiroshima City, Japan. I am posting about FCR carburetor and CBX1000 customization. I also post about things other than cars and motorcycles. We will post information that will make bikers around the world happy.
This article might be a bit rough. I've been curious about how the operation changes with and without a balance pipe, so I decided to write about it.
Results First: [No noticeable change]
The verification method was not very thorough, and it’s unclear whether the thickness of the balance pipe was appropriate. At least on a CBX1000, even if you install a balance pipe with the same outer diameter as the negative pressure outlet nipple, the effect seems minimal or unnoticeable. The inner diameter of the balance pipe matches the outer diameter of the negative pressure outlet nipple.
On the other hand, I didn’t observe any symptoms of inconvenience either.
Current Conclusion: A balance pipe seems useful mainly for improving work efficiency.
Before re-synchronizing, check for any differences between the balance pipe configuration and the blank cap configuration.
The premise is that if there are changes in idling or racing when synchronization is slightly out of sync, it indicates that the balance pipe is having an effect, whether positive or negative. However, the current method assumes that the balance pipes are functioning correctly, even if they may not have been installed properly.
It is possible that the pipe is too narrow and effectively functions like a blind cap.
The absence of any noticeable change also suggests that there are no issues with driving performance. However, those who have installed nipples on their FCR carburetors might feel a bit concerned.
For reference, the inner diameter of the balance pipe should match the outer diameter of the negative pressure outlet nipple. The connections are as follows:
・No. 1 to No. 6 ・No. 2 to No. 5 ・No. 3 to No. 4
These pairings correspond to the destinations of the spark plug wires.
I uploaded the video to YouTube.
A video will be played after the last synchronization. It may be helpful, but It may not be worth it if you know the outcome. Order ・Balance pipe arrangement ・Balance pipe and Foam Air Filter Sock ・Balance pipe and Velocity Stack ・No balance pipe. Mekura cap. Velocity Stack specifications ・Immediately after synchronization It becomes.
HONDA CBX1000-FCR-Balance pipe
work photos
Either a balance pipe or a blank cap can be used for the negative pressure outlet nipple.
What can be stated with certainty is that if the opening of the negative pressure outlet nipple is exposed directly to outside air, the engine will stall. This happens because the engine begins to draw in excessive secondary air.
The fact that the engine stalls indicates an issue with secondary air intake and suggests that the negative pressure outlet nipple is functioning as intended.
FCR Carburetor – The effects of the balance pipe【summary】
This type of verification is extremely important and will undoubtedly help someone in some way. However, since there were no negative changes observed, I’ll consider the current situation satisfactory as it is.
The verification and installation methods are quite complex, so if the balance pipe were installed using a more precise method, it might yield different results—or it might not. Upon reflection, if the tuning were such that a balance pipe had a significant effect, it seems logical that manufacturers would include the balance pipe specification as standard during production.
Personally, I feel the balance pipe doesn’t make much of a difference.
For example, with the CB750F, negative pressure can be extracted from the head, but it is typically sealed with a blind bolt. If the balance pipe were truly effective or completely free from issues, the manufacturer would have adopted it as standard. If it hasn’t been, it likely means either there’s a high risk of complications or that the pipe has no meaningful effect.
Understanding the effect of a balance pipe on a 6-cylinder engine might be challenging. The impact might be easier to discern on a 2-cylinder engine. At the very least, using a balance pipe instead of a blank cap for the negative pressure outlet nipple hasn’t caused any issues so far. In fact, it’s more convenient since it’s easier to attach and remove than a plug-type cap.
That said, I don’t believe further research into balance pipes will yield significant insights. While I’ll keep it in the back of my mind, I don’t think I’ll pursue further experiments. If an opportunity arises, I might give it another try.
Wishing you a fantastic FCR experience! See you again!
