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.
I often see discussions about the fuel economy of FCR carburetors, with opinions ranging from positive to negative. If I were to post about it on social media, it might spark arguments, so I’ve decided to share my thoughts in a blog column instead. Ultimately, the answer varies for each person.
I’ll focus on my experience with the CBX1000. I take pride in my ability to remove and install the FCR carburetor better than most. In terms of fuel economy, my CBX1000’s FCR gets around 12 km/L. I’m not sure if this is good or bad, as I rarely compare it with other CBX1000s.
With mindful riding, you can improve fuel efficiency. However, there were times when my fuel economy dropped as low as 7 km/L. When that happened, it was clear that something was wrong with the FCR. While I couldn’t pinpoint the exact cause, I suspect it was due to a strangely green slow jet. After disassembling and cleaning the FCR, I reset it, and the performance improved.
When I test-drove it afterward, it felt quite different. I’ve seen social media posts claiming fuel economies of around 15 km/L, which might be achievable for a well-tuned four-cylinder engine.
Another important factor is the rider's style. If the FCR is functioning well and tuned properly, fuel economy shouldn’t be drastically poor. I believe that good fuel efficiency often aligns with optimal tuning.
Should You Look for Fuel Efficiency in an FCR?
Since the FCR is a racing carburetor, fuel economy shouldn’t be the primary focus when tuning. The main goal should be to deliver the air-fuel mixture effectively. If fuel efficiency improves as a result, that’s a bonus.
To tune for better fuel economy, you can turn off the acceleration pump and aim for an air-fuel ratio of about 13.5 at throttle openings of 1/8 or more. Riding carefully can help improve fuel economy, but be aware that this tuning might make the acceleration feel somewhat lacking.
Avoid adjusting the slow jet, especially at low throttle openings, as it may hinder starting. As mentioned earlier, if your fuel economy is significantly poor, it’s likely that there’s an issue with the FCR tuning itself.
Driving Methods to Improve Fuel Efficiency
My Riding Techniques for Improved Fuel Efficiency When it comes to touring, I’ve found that the most fuel-efficient way to ride is to focus on keeping the oil temperature low. There’s no need to obsess over RPMs or rich/lean tuning; simply maintaining a lower oil temperature can significantly reduce fuel consumption.
On my CBX1000, I have a sensor installed on the oil pan that helps me monitor the temperature. I try to keep it around 80 degrees Celsius. With careful riding, it’s even possible to maintain an oil temperature below that threshold.
Seasonal factors also play a role. By concentrating on oil temperature rather than solely on RPMs, you can improve fuel efficiency. Keeping the oil temperature low naturally leads to lower RPMs, which can lead to a considerable increase in fuel economy.
However, this approach can be quite unenjoyable. Riding this way involves a certain level of stress, as it requires constant vigilance. If you relax your focus and accelerate even slightly, the oil temperature will rise quickly.
Does Tuning Improve Fuel Economy?
Does Tuning Improve Fuel Economy? Tuning can indeed improve fuel economy. By adjusting the engine to achieve an air-fuel ratio of around 13 to 13.5 at partial throttle openings of 1/4, 1/2, and 3/4, you can enhance fuel efficiency, although this may come at the cost of acceleration feel.
Reflecting on my early days, I once aimed for a partial throttle air-fuel ratio of 13.0. While this tuning allowed for normal riding, I noticed a significant lack of power during quick accelerations. This approach, while environmentally friendly, didn’t harness the full potential of the FCR carburetor.
If your goal is to boost fuel economy, consider turning off the acceleration pump. The ideal tuning for an FCR carburetor typically involves an air-fuel ratio closer to 12. I set my acceleration pump to engage at 1/2 throttle opening to strike a balance between efficiency and performance.
Fuel Efficiency – Forced Opening vs. Vacuum Type Carburetors
A forced opening and closing type carburetor operates by directly opening the throttle valve, allowing fuel to be drawn into the carburetor. In contrast, a stock vacuum-type carburetor uses negative pressure to adjust the air-fuel mixture more efficiently.
While the fuel economy of each type can depend on tuning, if both are optimized, the vacuum-type carburetor typically achieves better fuel efficiency. This is because the forced opening and closing type requires the rider to manually operate the throttle valve, which can lead to increased fuel consumption due to less precise control over the air-fuel mixture.
For FCR beginners – Tuning with an eye on fuel economy is okay at first.
If you’ve followed along so far, you’ll see that tuning specifically for fuel economy is somewhat of a paradox. Honestly, if your top priority is fuel efficiency, a racing carburetor like the FCR might not be the best choice. However, it's still valuable to experiment with eco-tuning to understand how your adjustments affect performance.
After establishing an eco-tune, consider shifting your focus to acceleration. You might find that tweaking the acceleration pump can address any power deficiencies from your eco-tuning. Eco-tuning is relatively straightforward: aim for an air-fuel ratio of 13 to 14 at partial throttle, which typically results in a smoother, more relaxed ride.
If you have an air-fuel ratio meter, try tuning with a ratio below 12 at partial throttle, and you may be surprised by the improvement in acceleration. At very low throttle openings, such as around 1/8, the air-fuel ratio becomes less critical. In these cases, prioritize ease of starting, smooth engine operation, and stable idling.
Improving Fuel Efficiency with FCR Carburetors【summary】
I have some doubts about whether tuning actually improves fuel efficiency, as I haven't tested it thoroughly yet. However, I do believe that tuning can significantly impact fuel efficiency during driving.
Personally, I focus more on oil temperature than RPM when riding. If you incorporate eco-friendly tuning into your setup, it might lead to slight improvements in fuel efficiency while using the FCR for travel. That said, this kind of tuning often results in a lack of acceleration, which can make for an unenjoyable riding experience. After all, many people install the FCR primarily to enhance power.
From my observations, eco-friendly tuning seems to provide only modest improvements in fuel efficiency, not as much as I initially expected. In my view, the most effective way to boost fuel efficiency is to ride in a manner that keeps oil temperature low.
There are definitely days when the temperature is just right for riding, so don't forget to perform maintenance as spring approaches. See you next time!
CBX1000 – Photo Gallery
I have gathered some photos from past posts showcasing individuals working on the slow jet. These images highlight various approaches and techniques, providing a visual reference for those interested in tuning their carburetors. Enjoy!
