Whether the vehicle is carbureted or fuel-injected, the fuel in the fuel system must be replaced regularly or it will deteriorate and cause sticking. If a motorcycle has not been ridden for a long period of time, the fuel inside the carburetor can turn into a varnish-like substance that clogs the passages, making it impossible to start the engine. In such cases, disassembly and cleaning are necessary, with particular emphasis on the slow and pilot systems.
Many riders may have an image of the main system when it comes to carburetors, but we will explain why the pilot system should be the focus of attention during the overhaul.
- Dissolve and remove varnish and dirt accumulated inside the carburetor with carburetor cleaner, not parts cleaner
- It is essential to check the ventilation of the internal passageways of the body where air passes through as well as the passageways where fuel passes through.
Dissolve and remove varnish and dirt accumulated inside the carburetor with carburetor cleaner, not parts cleaner
Even if there are no abnormalities in the external appearance, if the fuel inside the carb deteriorates due to long-term neglect, it becomes difficult to burn in the combustion chamber. This carb has a knob on the drain bolt of the float chamber that can be turned by hand, so if you know you will not be riding for a while, simply draining the fuel from the chamber will make it easier to start the carb again. The power filter facing the direction of travel needs more frequent maintenance, as it can cause water to be sucked in when riding in the rain.
There was no foul odor in the fuel in the fuel tank, but the inside of the carburetor, which was removed from the engine, was a soggy mess. The float valve opened and closed without any problems, which was good, but if dirt adhered to the valve itself, it would remain closed or open, causing overflow in the latter case.
Carburetor cleaner, not parts cleaner, is effective against altered fuel stains. Ys Gear’s foam-type carburetor cleaner envelops varnish and gum-like dirt and dissolves them powerfully.
If fuel is left in the fuel tank, its quality can deteriorate as early as a few months, resulting in reduced combustion power = harder to burn, and volatilization can leave varnish that clogs the passages. It is common to hear that when the carburetor or injection system is not in bad shape but the engine seems to lack power, simply replacing the fuel left in the tank with new fuel will revive the engine. It is fortunate if the engine recovers just by replacing the fuel, but if the fuel deteriorates further and sticks inside the carburetor or injection system, it can be troublesome. In the case of a carburetor, the fuel passage can be disassembled and cleaned directly, but the fuel pump and injectors of an injection car cannot be disassembled, so even if the ignition key is turned, there is no sound of the pump working, and even if the pump works, the injectors will not spray fuel, If the pump does not work when the ignition key is turned, or if the pump works but the injectors do not spray fuel, the parts themselves must be replaced.
The best way to prevent such a situation is to keep the fuel in the fuel system fresh, in other words, to ride regularly. In the case of carburetors, it is easier to recover from the symptoms than in the case of injection because it is possible to remove internal dirt by disassembling and cleaning. Brake and parts cleaner is a typical chemical for removing dirt, but for carburetors, “carburetor cleaner” is more suitable. Carburetor cleaner uses toluene and methyl ethyl ketone, which are not included in ordinary parts cleaners, to effectively dissolve fuel-based stains.
It is essential to check the ventilation of the internal passageways of the body where air passes through as well as the passageways where fuel passes through.
When cleaning the carburetor, remove all jets and needles as well as pilot screws and air screws that can be removed from the body. The pilot path, which functions when idling or running at low throttle opening, is often overlooked, but it is especially important for street driving, so disassembly is essential. Once the pilot screw is removed, all remaining parts on the body side, such as tension springs, O-rings, washers, etc., should also be removed.
Spray carb cleaner into any passage, whether fuel or air, to remove internal dirt. Depending on the passage’s inner diameter, the sprayed cleaner may flow back, but the passage must always lead somewhere, so if it does not come out from anywhere, it is considered to be completely blocked. Ys Gear also has a soaking-type carburetor cleaner, so if the spray type, which uses gas pressure to push dirt out, does not work, try changing the cleaner. Do not poke it with a wire or the like carelessly, even just to see how it looks.
Persistent dirt in the float chamber can be removed with carburetor cleaner, but the important part is to clean the jets and ports through which fuel and air pass. All parts that can be removed from the carburetor body, such as the pilot and main jets that meter fuel, jet needles, and needle jets, should be removed and soaked in cleaner, and at the same time, all passages and ports on the body side should also be sprayed with cleaner. Just as the jets meter fuel, the airports on the carburetor body are an important element in determining airflow.
If the ports that measure airflow in the slow and main systems become clogged, the airflow is insufficient for the negative pressure the engine is trying to suck in, resulting in extra fuel being sucked out of the jets and a thicker mixture. Therefore, removing dirt and debris from the air passages is as important as unclogging the jets. If the air passage is clogged when a cleaner is sprayed into the passage and it does not flow out from the opposite side, or if the amount of cleaner sprayed out is extremely small compared to the amount of jetting, the air passage may be clogged as well. Check the ventilation by blowing air blowers or parts cleaners.