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.
Since I had time to touch the motorcycle, I adjusted the FCR's Acceleration pump diaphragm.
Even though it is an adjustment, it is just a matter of replacing the diaphragm.
Acceleration pump adjustment has two items: discharge amount and timing.
FCR's acceleration pump is an obscure and incomplete device.
It is an unusual device that cannot be called precision like jets.
The discharge amount can be adjusted by replacing the diaphragm.
The larger size uses a standard size diaphragm, and the smaller size uses a KLX250 diaphragm.
The discharge timing is adjusted by the width of the tab on the FCR side as per the manual.
As for the timing, the 2.4mm is set so that it becomes effective from 1/2 throttle opening, and the operation check generally shows that it is discharged from 1/2 throttle opening.
Acceleration pump plate width
The width of the claw determines the starting position. 0mm is from fully closed 0.6mm is 1/8 1.2mm is 1/4 The manual only writes up to this point, but this time It seemed to be discharging at about 2.4mm from 1/2 throttle opening. The discharge start position will shift by 1/8 in 0.6 mm increments. I have never tried it, but I found that simply tuning it to 4.8mm turns off the FCR's acceleration pump. In reality, even with 5.0mm, it was discharged at around 3/4 of the throttle opening. It can be read as written in the manual, but it is an analog system, so It's better to take it in a rough way. I guess you're looking for accuracy, In terms of equipment, it's a very strange structure. Although the accuracy cannot be said to be high, the discharge start time is within the manual, so It is best to carefully measure and adjust the width of your nails. I tried measuring with a marker, but since there is throttle play and marker width, the accuracy is low.
For FCR beginners – Acceleration pump adjustment
@Necessary tools
・Caliper or thickness gauge
Measure the width of the claw, but it doesn't have to be that strict and you don't need to adjust it at first.
・3mm hex wrench, flat head screwdriver and pliers
Used to adjust the claws and attach/detach the acceleration pump.
@Replacement parts
・FCR standard (large) 1201-055-2102
・For KX250 (medium) 43028-0001
・For KX400 (small) 43028-0006
It looks like you can control it by rearranging it in these three ways.
@Note
- The direction of the diaphragm is that the side with the stamp faces the ground side when installed.
・Always turn off the gas cock.
We recommend that you first try replacing the diaphragm and compare the ride quality.
The conditions for beginners to try it out are that it is easy to touch and the before and after is easy to understand.
I haven't tried it with anything other than CBX1000, but there are probably enough changes that you can experience it. There is also a trick adjustment method that can be used to create a spacer collar such as a washer on the cover of the acceleration pump.
There is a way to suppress the diaphragm's return by holding something in between. Acceleration pump push rod
There seems to be a way to fix it and not press the Acceleration pump diaphragm, and turn off or adjust the function. I don't know much about the Acceleration Pump or touch it all the time, so I can't say for certain that it's good for beginners, but I think it's better to not have the Acceleration Pump.
But it's a wonderful system.
I don't think it's a good idea to put so much emphasis on incorporating imperfect things like acceleration pumps into the tunings. This will be added after the tunings are decided.
From that point of view, I reduced the discharge amount of the acceleration pump, and at the end of the tuning,
I try to make adjustments by increasing the discharge amount.
It's better if it matches, so it's better not to set it to 0 completely.
It's really fun to try out how things change, rather than just from a tuning standpoint.
work photos
My CBX1000 FCR is an old model, so acceleration pumps are installed in numbers 3 and 6.
Two parts need to be replaced. Replacing No. 3 and adjusting the pawl requires attaching and detaching the carburetor.
The feeler gauge is also 23mm, but the accuracy is slightly poor considering the angle and gap.
Lately, I've been liking richer tunings, At about 1/4 to 1/2 throttle opening, I felt like I was stuck, or rather, the accelerator wasn't following me. I was exchanging SJ. As part of this, we are replacing the acceleration pump diaphragm with a smaller size. It's unclear whether my riding style is bad or the tunings are bad. I can't say anything until I replace it and test drive it. I'm starting to feel like my riding style is bad, or maybe there's a problem with the throttle work. These points will also be used as a basis for judgment, regardless of whether there are any changes this time. Until last year, I used to touch it a lot, but recently, after touching it to a certain extent, I try to play with FCR by making predictions and making plans to try this next time. I would like to write a blog post about the next tunings that includes the test run. I hope you all have a fun FCR life. See you again!
