Disassembling the carburetors was definitely a significantly time-consuming task during this build. Though this was mainly the case as I spent considerable time attempting to zinc plate many of the small components. I explain the process I undertook with zinc-plating further below, however I do not recommend undertaking this task yourself.
In my case, the carburetor that came with the bike was from a Honda CB550F (carburetor model: 069A), not a CB500. As such, I had to set up the jets differently to account for smaller engine.
Disassembly
I began disassembly by removing all the carburetors from the back plate that held them together, as seen in the left picture above. Each carburetor was held on by two Phillips head screws. To remove each carburetor from the plate, the choke linkages between each carburetor has to be loosened to allow them to disengage each-other. The fuel-line linkages between each carburetor are press-fitted in with their o-rings, so you can remove by simply pulling them apart (as seen in the image below). There is also a centre spring that attaches to the throttle mechanism on the back plate, that can be removed with pliers

The base plate has the attached throttle mechanism that requires disassembly as seen below. Referencing the image below, the idle control screw on the left hand side can be simply unscrewed along with the associated spring. The plate can then be removed via the two small Philips head screws.

The below image shows the rod that rotates when the throttle pipe on the handlebar is rotated. This pulls on the throttle cables that then push and pull on this rod to rotate it. The two lugs (I am holding one in my hand below) then move up and down to open the carburetor slides. On the centre of the rod houses the mechanism that holds the throttle cable nipples and springs that keep the slides closed with the throttle is pulled.

The two lugs could be loosened by their Philips head screws. The centre assembly is held in place by clamps with M10 bolts. By loosening these two bolts, the centre assembly could then be slid along the rod. From here, the rod could be pulled out.


Individual carburetor body disassembly
In this section, I’ll discuss the disassembly of the carburetor bodies. Given each one is almost identify (expect for minor differences due to their relative position), I will discuss the disassembly of only one. IMPORTANT: When you are disassembling the carburetors, ensure you stay organised and don’t mix up the components between the carburetors. There are many tiny parts that are easy to lose.
I began by removing the top cap of the carburetor body. This is held in by two screws. Once this is removed, you will see the slide assembly within the carburetor as seen below.

The very top nut has tonged washer that needs to be bend flat in order to allow you to screw it out. This bolt can be removed with a 5mm socket. Once this bolt is removed, you can rotate the linkage to allow the slide to move up in the carburetor, allowing easier access to the bottom nut. The bottom nut does not have a tonged washer and can be removed with a 6mm socket. When you remove this, be EXTRA careful, within the nut there is a dimpled metal that allows movement on the linkage ball joint. This small piece of metal can fall out and can be VERY easy to lose (I should know, I spend a good half an hour finding one I dropped. Doh!). Once this nut is removed, you can remove the linkage from the slide assembly and then proceed to pull it out.
The linkage below can then be pulled out of the carburetor body (ensure you take photos so you remember the order of all the washers, springs, etc).

On the air-box side of the carburetor body, the choke butterfly valve can be removed via two small Phillips head screws (see left image below). The butterfly valve linkage can then be removed by unscrewing the 6mm brass bolt.



Zinc-plating
Given many of the parts on the carburetor were rusted, I thought it would be a fun challenge to zinc plate them myself. In hindsight, whilst it was definitely a (somewhat) fun challenge, the amount of time I spent performing trial and error to get the solution correct just wasn’t worth it. So whilst I do provide a brief description of the process I followed below, I do not recommend doing this yourself. For other parts on the bike, I decided to get it zinc plated at a local zinc-plating workshop, which was both reasonably priced and had a quick turn-over.
Parts/equipment required:
- Parts/equipment required:
- Copper pipe
- Epson salt
- Vinegar
- Glucose sugar
- Zinc anode
- Power supply
I used this forum post to assist me with the process. It involved significant trial and error to find the sweet spot with each component, however that post provided a good starting point to base my electroplating on. I found that the surface area of the parts being plated had a big impact on the overall finish. To help maintain a consistent finish, I attempted to keep this surface area around the same for each batch. Unfortunately I did not have an adjustable power supply so this was the only option I could use to vary the finish.
Before starting the process for electroplating with each part, I would ensure they were thoroughly cleaned. I would wire wheel each part and use wax & grease remover to ensure there were no contaminants.
Below you can see the setup I used for electroplating. As you can see, it is quite time-consuming placing each small component on the copper wire and placing it in the solution.

I would have them bubbling away in the solution for around 20 minutes and then pull them out and then rub them with a scotchbrite pad. I would continue to do this until each part was completed plated. From here I would then polish with brasso and bring up a shine on each part.
After rinsing and repeating this process on multiple components, the results were definitely significant. The zinc plating has a lighter silver finish compared to raw steel. The pictures below show some of the results I obtained from my DIY electroplating process.






Carburetor restoration/rebuild
With all the smaller metal parts electroplated, I also had the carburetor bodies vapour-blasted. This brings the metal back to it’s original brightness and means I didn’t have to repaint them (which I imagine would have flaked after some time, especially given the possibility to come into contact with fuel).



The carburetor top-caps and float bowls were also sanded and polished.
I carburetor rebuild kits for each carburetor from 4into1.com, specifically for the 069A carburetor I had. This included all the required o-rings, jets, etc to build each one. However, unfortunately my carburetor was missing the floats, needle pin holder and the float stop bracket that attaches to the main jet. Given the original state of the bike, I imagine the carburetor was just one they had floating around, especially given it wasn’t the same model used with the CB500 engine.
Much like any good workshop manual, I’ll simply say that assembly is the reverse of assembly. I kept all photos of the disassembly to make this process significantly easier. The final result can be seen below.



