Let’s Practice Disassembly and Maintenance of Dirty and Sticking Carburetors from Boiling the Kettle.

The carburetor is a part that cannot be turned a blind eye when rebuilding an immobilized vehicle. It is not uncommon to find that the throttle cannot be opened or closed due to a completely sticking carburetor. It is good to remove the carburetor from the engine, but how to disassemble the sticking parts? What we recommend here is a disassembly setup using a pot and boiling water. Here, we report on our disassembly challenge of a sticking 4-cylinder carburetor.
I would like to draw your attention to this work setup.

Working methods vary depending on the degree of adhesion.

A four-stroke carburetor appeared to have been removed from the bike and left in the barn for a long time.
The throttle valve and by-starter function were completely stuck, and it was difficult to even disassemble the carburetor before overhauling it.
Let's try a rough cleaning method called "washing the whole carburetor = boiling it in a kettle.

If you cannot disassemble it smoothly

Do not forcefully coax in a sticking condition.

In fact, when I noticed the completely sticking situation, I applied plenty of anti-rust lubricants penetrating spray around the throttle valve and warmed up the body with a heat gun, but the sticking throttle valve was not improved.
It has been a long time since I have seen a carburetor sticking this badly, but a heat gun is essential for carburetor maintenance. However, there are times when a badly sticking carburetor can be irresistible. We should not disassemble the carburetor forcibly in a completely sticking condition. Do not try to pull it out by hooking a screwdriver on the cutaway of the throttle valve and using leverage.

Setup before kettle boiling and washing

Since the sticking may be caused by more than just the throttle valve, I removed the top cover, removed the throttle linkage, and freed the piston. The throttle valve should be completely free at this stage, but the valve is at the very bottom and completely stuck. There is no sign of movement at all. Do not forcefully pry it out with a screwdriver or the like. Since we had no choice, we disassembled all the parts that could be disassembled, leaving the sticking valve in place. The air screw came off smoothly, and there was no evidence of a crushed needle tip. While the carburetor was completely seized, it may be a carburetor with a good basic level. In order to manage and restore the disassembled parts of each cylinder, I cut a plastic bottle with a cutter and made a sorting container by myself.

Pots, Tap Water, Chemicals

I decided to wash the entire carburetor using a small skillet pot. I mixed Hanasaka G Multi-Cleaner in hot water heated by a portable gas stove and used hot water + cleaning chemicals to effectively dissolve adherence. I couldn't wash the whole 4-cylinder carburetor at once because the size of the pot wasn't big, so I washed 2 cylinders at a time. Warm the entire body with hot water while washing. The other side was also turned over and continued to be cleaned. I took a picture of one side washed, and the difference is obvious. The first/second side is before washing and the third/fourth body is after washing. The difference is obvious.

The final touch is again chemical.

All four carburetors were cleaned by boiling them in a kettle. The throttle valves now work slightly. Then, after spraying the cleaning chemical for carburetor cleaner, I warmed up the body with a heat gun. The throttle valve started to move, although it was still sticky. For the first time, I pried the throttle valve with a screwdriver, and the valve lifted up smoothly without any force. Disassembly succeeded

The Mikuni carburetor for the Kawasaki air-cooled 4-cylinder carburetor has finally been disassembled and set up.
We will now begin full-scale disassembly and overhaul work. The difference is obvious if you compare the images with those before disassembly. But it is still only the completion of the disassembly setup.

The carburetor may malfunction due to not being ridden for a while, resulting in unstable idling or poor starting, even though the engine used to run fine after starting. Starting with the first step, we decided to practice disassembling and maintaining a 4-stroke carburetor. The carburetors were clearly in need of an overhaul, but it was not just their appearance; the throttle valves were completely stuck in place without opening or closing. Therefore, we decided to wash the whole machine as a setup for disassembly work.
This whole washing = boiling in a kettle makes it easier to disassemble the machine later on.

It is natural that the condition of parts that have been left for a long time in the condition of a complete bike and parts that have been left for a long time in the condition of single parts would differ, even if they were stored in the same place. Parts such as carburetors are particularly prone to make a big difference. When installed in a motorcycle, the front and rear of the carburetor are blocked by insulators and air inlet pipes, making it difficult for water and dirt to directly enter the carburetor. On the other hand, the cab and fuel tank are connected by a fuel tube, so there could be situations where fuel could flow into the carburetor.

In some cases, if the cab is left as a single unit, moisture, dust, and other contaminants can easily get inside the cab and cause the condition to deteriorate more than expected. In this sense, when storing parts by parts, you may wrap them as tightly as possible in plastic bags, paper bags, or, depending on the situation, in plastic wrap for securing packaging.
Of course, it would also be important to remove the float chamber, drain the fuel, and blow the air. In short, it is important to store them in such a way that they do not deteriorate beyond their current condition.

The 4-engine carburetor to be disassembled and maintained here is a Kawasaki air-cooled 4-engine Mikuni.
Unfortunately, the throttle valves were completely stuck due to the long period of neglect and fuel residue in the carburetors. Every other moving part, including the other parts, was locked up.

For such a carburetor, disassembly itself is a troublesome task before overhaul. If disassembled too aggressively and carelessly, it is possible to cause serious damage to important parts, so care must be taken. Heat is an extremely important ally when disassembling such a carburetor assembly. In many cases, when a sticking carburetor is disassembled, warming up the entire body will dissolve the fuel varnish or tar that is the cause of the sticking, and the sticking moving parts will start moving. Here, I report on the disassembly setup using the whole carburetor body warming method, which can be achieved by using heat to warm up the entire body.