FCR Tuning – Please check if the pilot screw is working correctly

FCR Tuning – Please check if the pilot screw is working correctly

The other day, I received various questions about screws and FCR in real life. I will be writing a blog about the pilot screw. The following links are also easy to understand. The amount to turn back the screw is indicated in clock notation: 90 degrees = 30 minutes, 360 degrees = 1.00 minute.

↓Link to previous posts↓
FCR Tuning – The pilot screw can be fully closed to allow idling.

As the title suggests, this is a column about checking whether the pilot screw is working correctly. If adjusting the pilot screw seems difficult, it is acceptable to fix it at 1.00 turn out. Some people do not touch the pilot screw when tuning the FCR.

The engine can idle even with the pilot screw fully closed.

If you deliberately adjust by making the slow jet extremely large and setting the idle stop screw higher, the engine can idle even with the pilot screw fully closed. Sometimes, the engine can idle and start without issues whether the pilot screw is fully closed or set to 4.00 turns out. If you can notice a change after turning the pilot screw 30 minutes from 1.00 turn out, then the slow jet is of the appropriate size.

When adjusting the pilot screw, please use a pilot screw adjusting tool while the engine is running. When I first started tuning the FCR on my CBX1000, I couldn't find a pilot screw adjusting tool that fit, so I tried making adjustments with the engine off, but it was hard to tell if there was any change. The pilot screw adjusting tool I use for the CBX1000 has been modified by shaving it down. After borrowing and testing three different tools from motorcycle shops, none of them fit properly without interfering with the engine.

For the CBX1000, a pilot screw adjusting tool is essential when adjusting the pilot screw. My CBX1000 is equipped with an air-fuel ratio meter. The first time I used the pilot screw adjusting tool to adjust the pilot screw while the engine was running, I was surprised by the significant changes.

Does adjusting the pilot screw affect engine startability?

It does change. The air screw also causes changes. The air screw affects throttle openings from 1/16 and above. If it can be adjusted with the pilot screw, it should be done that way. The engine can idle even if the slow jet is too large. Do not proceed with tuning using a slow jet size that renders the pilot screw ineffective. This will lead to poor balance and make future tuning difficult. When I was a beginner, I used to fix the pilot screw at 1.00 turn. I regret not using a pilot screw adjusting tool from the beginning.

Should the pilot screw be adjusted for each cylinder individually, or should it be averaged?

On my CBX1000, I was unable to feel any changes even when adjusting the pilot screw for each cylinder individually. There might be issues with the method or preconceived notions. In my case, I set the same adjustment amount for all cylinders. The tuning manual does not specify that the pilot screw should be adjusted for each cylinder individually. Since the air screw allows for separate adjustments for each cylinder, balance can be achieved.

FCR Beginners – It’s okay to fix the pilot screw.

If the engine idles properly, it's fine to leave the pilot screw at 1.00 turn out. The pilot screw mainly affects idling, so adjusting it generally does not significantly impact power during riding or cause major issues. The goal is to balance it somewhat with the slow jet and air screw. While it is better to make adjustments if possible, it's not a problem if you can't. Generally, if the pilot screw is set at 1.00 turn out and the air screw is between 45 minutes to 1.45 minutes return, and if there isn’t an extreme lack of power during clutch engagement at start-up, the pilot screw adjustment is likely close to being correct. However, it's important to address this adjustment if possible.

FCR Tuning – Please check if the pilot screw is working correctly【summary】

n summary, checking whether the pilot screw is effective can indicate if the slow jet is the correct size. This article was a column on the pilot screw. I've written similar content several times in the past, and the information has been updated over time. The next post will include even more updated content. See you again soon!

CBX1000 Photo Gallery

I will include images from past posts that show adjustments being made to the pilot screw in FCR tuning. I will also include images of the pilot screw adjusting tool. Please note that the names in some photos may differ.