How much gasoline is accumulated in the float chamber of the FCR carburetor?

How much gasoline is accumulated in the float chamber of the FCR carburetor?

Here’s the conclusion first: For the FCR on the CBX1000, it holds around 100cc to 150cc of gasoline.
I may have posted something similar in the past.
This is an approximate amount, so there could be some variation.
When I changed the slow jet, I took a quick photo.
I’ll go over how to handle the gasoline when changing the main jet or slow jet on the FCR.
This is more of a trivia post about the FCR.
Feel free to use it as a conversation topic when you're out touring or during lunch, when the subject of the FCR’s float chamber comes up.
Now, let's get started!

This time, it’s 100cc.

I drain the gasoline accumulated inside the FCR carburetor by turning it upside down and letting it out through the air vent.
You can also drain it from the drain bolt.
However, the O-ring on the drain bolt can sometimes wear out.
Be careful when loosening it and make sure to check it after reinstallation.

The gasoline has been drained from the air vent.
This time, I collected about 100cc.

Here are 4 key points where gasoline leaks can occur in the FCR carburetor

Here are some examples of instances when gasoline leaks or seepage have occurred:

1. Chamber Gasket
2. Accelerator Pump Diaphragm
3. Drain Bolt
4. Quick Gas Joint
These are areas you'll frequently handle during FCR tuning. If you notice gasoline seepage or leaks, replace the gaskets immediately. Tightening the cap bolts or applying liquid gasket sealant will not resolve the issue.

Gaskets for points 1 and 2 are not typically available at home improvement stores, so keep spares on hand when tuning outdoors. For point 2, in addition to the accelerator pump diaphragm, there are also O-rings and U-rings. Be careful not to lose them. The U-ring has a specific orientation: the flat side should face downward.

Pay attention to the orientation of the accelerator pump diaphragm as well; the side with the markings should face downward. It will still function if installed incorrectly, but it’s not ideal. Handle with care during installation and removal.

The quick gas joint (point 4) is inherently prone to gasoline leakage. Always carry spare O-rings.

↓Previous Posts↓
4 points to note about gasoline leaks during FCR tuning

Draining gasoline from the air vent

When you turn the FCR upside down, gasoline will come out of the air vent. Although some gasoline may remain in the fuel line, it's best to drain as much gasoline as possible before starting work.

The air vent is originally a pipe for releasing air from the chamber inside the FCR. Gasoline will also overflow from this pipe if there's an excess. This pipe allows both gasoline and air to enter and exit.

The air vent can sometimes break or crack. Since it's made of plastic, it's best to avoid exposure to chemicals and prolonged direct sunlight.

Note: My FCR has been trouble-free for about 20 years.

Be cautious of gasoline mixing with oil.

Additionally, when an overflow occurs, be sure to check the oil. There are cases where a large amount of gasoline has flowed into the engine. If you open the oil filler cap, you may find that the oil smells of gasoline and is in excess. This issue is more commonly seen during storage rather than while riding.

For FCR Beginners – Pay Absolute Attention to Gasoline Leaks and Overflow

Here's how to address overflow issues that occur while riding:

In most cases, overflow is caused by debris obstructing the fuel adjustment valve, which is the float valve. The quickest way to understand how the float valve works is to disassemble the carburetor and manually check its operation.

Sometimes, vibrations applied to the carburetor or draining gasoline from the drain bolt can help dislodge any debris. Try these methods if you experience overflow.

Be aware that gasoline leaks or seepage can lead to serious accidents, including fires. If you notice any fuel odors or discoloration around the engine, check for gasoline leaks immediately.

How much gasoline is accumulated in the float chamber of the FCR carburetor?【summary】

During this removal and reinstallation, there was slightly more gasoline accumulated than 100cc. For precise measurement, you'll need to drain the gasoline from the drain bolt.

The gasoline collected in the measuring cup is returned to the sub-tank and used for synchronization work.

Although we’ve covered the topic of gasoline leaks, I’ve outlined the trouble spots that are likely to be encountered when tuning an FCR. I hope this information serves as useful background knowledge for when you encounter these issues.

Please take care to avoid heatstroke and enjoy your FCR life!

CBX1000 – Photo Gallery

I’ve selected and included photos related to previous posts.