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.
FCR Tuning – Test Ride with Awareness of Shift Position – 2023-06-17
Recent Tuning Focuses on Rough Throttle Work.
I'm still not quite able to tune it perfectly yet. Recently, I had the opportunity to ride on the highway. During the ride, I noticed something: I realized that I haven't been tuning with much attention to the shift position.
The CBX1000 has a 5-speed transmission. When evaluating the main jet (MJ) with full-throttle runs, I consider the following:
・In 3rd gear, does it rev up smoothly from 6000 RPM when fully opened? ・In 4th gear, does it rev up smoothly from 6000 RPM when fully opened? ・In 5th gear, does the speed increase when fully opened?
My CBX1000 is equipped with an AS Uotani ignition system, and if I rev the engine too much, the limiter kicks in and causes misfiring. So, I make sure to be careful not to over-rev the engine while riding.
While I was aware of the shift position during full-throttle runs, I didn’t pay much attention to the shift position when tuning for situations other than full-throttle runs, focusing mostly on throttle opening instead. While the throttle can be operated roughly, there's no need to shift gears roughly.
I only use 1st gear for starting. Instead of focusing on smooth throttle work, this blog post is about tuning with the shift position in mind, carefully building up speed, and adjusting the AS and jet needle (JN) clip position accordingly.
There wasn’t much change with the PS. I decided to keep it at 1.00 turn out for now to see how it goes. If there are no issues with the PS, I’d like to keep it at 1.00 turn out. I prefer the leaner clip position. I'm still testing the accelerator pump's discharge timing during the test rides.
I don’t change the shift position at low throttle openings until the speed picks up
I'll explain what specific actions I took and what effects they had. I feel like I forgot something important: not changing the shift position until the speed fully picks up.
Naturally, if you decelerate by releasing the throttle while accelerating in 3rd gear and then try to accelerate again, you'll notice a lack of torque due to the gear ratio. When tuning, you should ride in a way that minimizes moments of low torque as much as possible. It's obvious that gear changes are meant to aid acceleration. The idea of not changing the shift position until the speed is fully up isn't anything extraordinary; it's just common sense. However, people tend to forget these basics as they become more familiar with riding.
It's crucial to always aim for maximum acceleration from any speed or condition. Since carburetors are analog devices, they won’t accelerate as intended unless the rider performs the appropriate actions. Therefore, the rider must consciously control the shift position and throttle work. Until recently, I was only focused on throttle operation. If you want to work the throttle roughly, you need to handle the shift position carefully while tuning.
In short, when trying to increase speed, it's important to consider the engine's RPMs while tuning.
FCR Beginners – What Should Be Done Specifically with the Shift Position?
In this blog post, I’m writing as if I were a beginner myself. By putting it into words, I realize many things.
When tuning with the throttle opening at 1/4 or less, it’s important to avoid changing gears until the speed has fully picked up. Here are the points to check:
1. When starting, use 1st gear up to around 20 km/h. 2. Up to about 40 km/h, stay in 2nd gear. 3. From 40 km/h to 80 km/h, stay in 3rd gear.
Choosing the appropriate shift position based on speed is crucial during test rides while tuning. You also need to be aware of the engine RPM.
One mistake I made was trying to see if 2nd gear was suitable for the speed range when I was actually in 3rd gear. Naturally, the power feel decreased, and the response wasn’t as satisfying.
It’s important to set the shift positions according to the speed range. If you frequently need to make sudden decelerations or accelerations, adjusting the shift positions accordingly during test rides is essential.
FCR Tuning – Test Ride with Awareness of Shift Position – 2023-06-17【summary】
The FCR is a racing carburetor, so it's normal to ride with higher RPMs to some extent. When riding mainly in the city, you might choose gears that offer less power and keep the RPMs lower. Lower RPM riding improves fuel economy and prevents the engine from revving too high.
When tuning, you shouldn’t focus on fuel efficiency. Instead, the rider should use their skills to manage fuel economy with the FCR.
For the time being, I will focus on the shift positions and speed perception while tuning the FCR. I hope you all enjoy your FCR life. See you again!
CBX1000 Photo gallery
Here are photos of the CBX1000 taken during the tuning process. The center stand is up, and the photos are taken from all directions.
