FCR Tuning – Acceleration Pump Discharge Timing Adjustment – 2022-10-12

FCR Tuning – Acceleration Pump Discharge Timing Adjustment – 2022-10-12

I had time today, so I adjusted the discharge timing of the accelerator pump in the evening.
Previously, I tried changing the discharge timing from time to time, but basically it was fixed.
Previously, only the total discharge volume was changed by replacing the diaphragm.

Previous articles about [How to turn off the accelerator pump] and [Direct fuel hit on the throttle valve]
It has been described.
You will enjoy this story even more if you read that first.

FCR Tuning – Easy way to turn off the acceleration pump

FCR tuning – Acceleration pump adjustment – If it is too fast, it will hit the throttle valve.

This time, we will only change the discharge timing.
Confirm with a feeler gauge in increments of 0.3 mm, including test runs.
The acceleration pumps of the old CBX1000 FCR are attached to numbers 3 and 6.
Two changes are required.
It may be a sloppy adjustment, but I will write a rough impression.
Adjustment of the FCR accelerator pump can be changed in two ways: discharge timing and total discharge volume.
The mechanism is the same as a water gun. It controls the discharge timing and total discharge amount of the water gun.
It will be tuning.

Discharge timing adjustment and influence range

Looking at the range of influence in the tuning manual, it is in 0.6mm increments.
There are individual differences for each motorcycle or FCR.
There are also cases where the claws become strange due to too much adjustment.
When you actually move the claws to make adjustments, it is difficult to make adjustments with an accuracy of 0.1mm.

I did a test drive while adjusting in 0.3mm increments.

① Off
②1.6mm
③1.9mm
④2.3mm
I compared it with
③ seemed relatively good to me.
② depends on the timing of opening and tightening the throttle.
We have confirmed cases where fuel injection directly hits the throttle valve.
This time, we adopted ② 1.9mm.
It is the season of autumn. Perhaps the tuning has changed, or perhaps the discharge timing is better tuned, but I get the feeling that I can experience the state of accelerating by adding fuel through the sound and speed.
It may be a placebo effect, but the act of twisting the throttle is extremely fun.

Becomes rich when opening the throttle suddenly

When I suddenly open the throttle, the air-fuel ratio meter reads 10.0.
My air/fuel ratio meter is a PLX DM-6.
I've always thought it strange that the car becomes richer when the throttle is opened rapidly.
Lately, I've been feeling that the numbers indicate a richer direction because fuel is added with the accelerator pump.
A situation where the A/F meter (air/fuel ratio meter) shows 10.0 for a long time when the throttle is suddenly opened is
The fuel is getting too rich.
I believe that if you open the throttle too quickly, the fuel that is slowly pumped out by the accelerator pump will be pumped into the engine all at once, making it rich.
For example, if the discharge start timing is 1/4 of the throttle opening, if you suddenly open the throttle from 1/8 to 1/2, the fuel that is gradually discharged in stages will be sent all at once.
If you keep the throttle at 1/2, it will feel like it waits for a while and then suddenly accelerates. I believe that riders need to be able to control the sudden opening of the throttle with their own hands to some extent. Of course, the type and characteristics of the motorcycle also play a role.
I felt that the FCR is not a carburetor that does rough throttle work.
It is easy to tune the accelerator pump by looking at the air-fuel ratio meter.
The numbers are true. If the numbers are strange, there is something wrong with the motorcycle.

For beginners in FCR – Adjust the discharge timing of the accelerator pump.

About 20 years ago, there was little information about FCR tuning.
The custom shop was kept secret.
What was written in magazines became a trend in the world.
Magazines at the time said that it was better to turn off the accelerator pump, and that there was no need to touch it.
That's my idea.
It is recommended for beginners to play around with changing the characteristics of the motorcycle by tuning off the acceleration pump and adjusting the discharge timing.
There is no need to purchase a new one like jets.
No disassembly required.
Trends may change with the times, and some knowledge may be incorrect.
Even if you change the discharge timing of the accelerator pump, the motorcycle will not be damaged, and you can quickly restore it.
You can also turn it on and off with a single stationery clip.
Changes are also easy to understand.
Please try various things.

FCR Tuning – Acceleration Pump Discharge Timing Adjustment – 2022-10-12【summary】

My impression after this adjustment was that adjusting the discharge timing of the accelerator pump was very fun.
My current preference is to reduce the total discharge volume of the accelerator pump and adjust the discharge timing.
I'm using the throttle at a fairly high speed, so it may be related to throttle operation.
Previously, the throttle opening was fully open at 90 degrees, but now it is fully open at 56 degrees.
These points also have a considerable influence on FCR tuning.

This is when the throttle opening is fully open at 90 degrees.
I've never noticed that it gets too rich when the throttle is suddenly opened. If you feel that something is strange or unusual, try researching it consciously, search the web for advice from those who have come before you, or ask your seniors in your neighborhood.
I like the current tuning, so I'll give it a try this weekend.
Please make sure to properly prepare your bike for this weekend's touring.
See you again!

*Photos are added at the bottom.

Photos from the test run on 2022-10-12

There is a mountain road behind my workplace, so I test drive it in the evening to tune it up.
It's a nice change of pace.
Photos will become good memories, so please be sure to take photos.