FCR tuning – MJ exchange, 122 → 118

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FCR tuning – MJ exchange, 122 → 118

I replaced the FCR main jet from 122 to 118. I wanted to do this without removing and attaching the cab and tank, but I couldn't reach them, so I only removed cabs 1, 2, and 3 by slightly shifting them.
The other day on the expressway, I was accelerating and it was too rich to measure, or about 10.6, and when I opened it slowly, it was about 12.3 partially.
Even when I opened it slowly, it was about 12.3, so even 118, which is two steps from 122, won't be too thin.
There shouldn't be. Even if you never use full throttle, there is a big difference between being able to use full throttle or not.
If you're tuning up something as a hobby, you'll want to make sure it's usable even when you're not using it.
To be honest, it can be used up to about 2/3 of the throttle opening. Trying to open the throttle fully on a public road is not enough to save your life, so you should do it in moderation.
I feel like if I try it on a public road, I'll die about twice.
Even when I test drove it on the expressway, the AS Uotani SP2's limiter reached its limit fairly quickly.
The only thing you can do is consider the surrounding traffic situation, check to see if there are any animals, etc., and try driving at full throttle.

MJ replacement work

FCR-Main jet set
FCR-Main jet set
FCR-Drain bolt
FCR-Drain bolt
MJ can be replaced even with the FCR installed by simply removing the drain bolt at the bottom of the FCR.
The part where gasoline is stored is called the chamber.
However, fuel will leak out.
Work efficiency can be improved by attaching and detaching the cab. You can also receive fuel in a cup.
The reason for replacing the MJ with the carb installed is because you don't want to remove the adjusted throttle wire.
You can remove the carb with the throttle wire attached, but you don't want to put stress on the area around the throttle wire. However, it is difficult to replace the MJ without shifting the carb, so remove the FCR carburetor by shifting it a little.
Another thing to keep in mind is that if you roughly remove or tilt the cab, it may cause an overflow, so be careful to do so in moderation. Carburetor overflow is usually caused by debris trapped in the float valve. Tapping the suspected overflow carb or disassembling it and removing any debris should resolve the overflow. You may not be able to find trash even if you visually inspect it. You can often fix it by disassembling it and checking it by hand to see if it is working correctly. Naturally, if you turn it over too much, dirt and rust will be more likely to pick up on it.
I'll try it out tomorrow or over the weekend and see how it goes.
The time required for replacement is approximately 15 minutes. There aren't many tools and it feels like they can be easily replaced. As a side note, the front fender line is one of my favorite customizations.

FCR tuning – MJ exchange, 122 → 118【summary】

I suspect that even if you change MJ from 122 to 118, it won't make much sense.
I feel like all I have to do is check the air-fuel ratio meter to see how much it has changed.
However, you won't know anything unless you try it, so if you are interested, you have no choice but to replace it and try it out.
This is a maintenance issue, but it's not limited to CBX, but when replacing MJ with no look, you need to be careful not to overtighten.
MJ is made of brass. If you tighten it too tightly, the threads will break.
That would be very sad.
I cut a thread once. I wasn't on the go at the time, so there was no problem, but it would be a bit painful if I were to cut the thread without a spare MJ on the go.
If you replace MJ, you can recover because there is a different count.
However, the biggest problem is that the screws are about to break and you end up driving with the FCR installed.
When this happens, it is difficult to notice the problem.
Even if something seems wrong, it is not uncommon for it to take some time to investigate the cause.
Please be very careful.
Based on my experience with the test run, there is a possibility that the accelerator pump tuning is too high when the throttle is fully open, so I think it might be a good idea to set the accelerator pump diaphragm back to a small tuning and then try fully opening the throttle. If possible, I would like to leave the accelerator pump as high as possible and arrive at a tuning that satisfies me, but I think it will depend on actual riding. While I'm writing this, I'm going to do some research to see if it's possible to delay the discharge timing of the accelerator pump and then reduce the total discharge amount when the throttle is fully open. Either way, I'll return it to the rental garage tomorrow. Before that, I'll be sure to measure the fuel consumption.
Well then! Have a good FCR life!
See you again!
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