Sylvie Willis
The fuel valve on a motorcycle is commonly referred to as a petcock. It is essentially a fuel gauge that regulates the flow of gas from the tank to the engine. The petcock valve has three positions: On, Reserve, and Off. When the fuel level drops below the 'On' tube, the bike will start to stumble, at which point the rider switches to the 'Reserve' position. The 'Off' position is used when the motorcycle is not in use or when the fuel system needs to be drained for maintenance.
Motorcycle Fuel Tank Valve Characteristics and Values Table
| Characteristics | Values |
|---|---|
| Name | Fuel Petcock |
| Other Names | Inline Fuel Shut-Off Valve, Chopper Fuel Valve |
| Function | Controls fuel flow to the carburetor |
| Positions | On, Reserve, Off |
| Tubes | Generally two tubes, one taller ("On" tube) and one shorter ("Reserve" tube) |
| Use | When the tank is ~1/4 full to completely full, use the "On" tube. When the fuel drops below the "On" tube, switch to the "Reserve" tube until empty. |
| Maintenance | Switch to "Off" when not riding or to drain the fuel system. |
| Variations | Sizes: 22mm, 1/4", 3/8"; Finishes: black, chrome, brass |
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What You'll Learn
The fuel petcock is a three-way valve
The fuel petcock, also known as a petrol tap in the UK, is a small shut-off valve that controls the flow of fuel on a motorcycle. It is the old-school version of a fuel gauge, allowing riders to switch between the "on," "reserve," and "off" positions. The "on" position is used when the fuel tank is between one-quarter and completely full, while the "reserve" position is used when the fuel level drops below the high "on" tube. The "off" position is used when the motorcycle is not in use or when the fuel system needs to be drained for maintenance. Some motorcycles may also have a "prime" position for vacuum-operated petcocks.
The fuel petcock is typically located on or near the fuel tank and is essential for proper engine performance. It ensures that the engine receives an adequate fuel supply, and when the level of fuel drops below the "on" tube, the motorcycle will start to stumble, indicating the need to switch to the "reserve" position. The "reserve" position accesses the bottom portion of the fuel tank, allowing riders to reach the nearest gas station.
The fuel petcock has evolved from threaded valves controlled by a butterfly handle to modern ball valves. While ball valves provide coarse control compared to gate valves, they are suitable for on-off applications. Motorcycles with older engines may still use the fuel petcock, and replacements are available in various sizes and finishes to fit different models.
Understanding the fuel petcock is crucial for motorcycle maintenance and operation, especially for older models that lack a fuel gauge. By mastering the three-way valve positions and their functions, riders can ensure a smooth riding experience and avoid fuel-related issues. Regular checks and adjustments of the fuel petcock can help prevent unexpected stalls and ensure efficient fuel usage.
In addition to motorcycles, petcocks are also used in other applications, such as draining water from diesel fuel water separators in trucks and verifying combustion in submarine engines. They play a vital role in ensuring the proper functioning of engines and fuel systems across various industries.
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$6.29
It has three positions: On, Reserve, Off
The fuel valve on a motorcycle is commonly referred to as a petcock. This is a three-way valve with three positions: On, Reserve, and Off. The "On" position is used when the fuel tank is between one-quarter full and completely full. When the fuel level drops below this, the bike will start to stumble, and you'll need to switch to the "Reserve" position. This position uses a shorter tube to access the remaining fuel in the tank. The "Off" position is used when the bike is not in use or when the fuel system needs to be drained for maintenance.
Some motorcycles may not have an "Off" position, and some may have a "Prime" position for vacuum-operated petcocks when the bike runs out of fuel before filling up. The petcock acts as a fuel gauge, helping riders understand their fuel usage and plan their refuelling stops.
It is essential to ensure proper gas flow for optimal engine performance. If the fuel petcock needs to be replaced, various options are available in different sizes and finishes, including black, chrome, and brass.
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The On tube is taller and reaches higher into the tank
The fuel petcock on a motorcycle is a three-way valve with positions labelled "On", "Reserve", and "Off". Inside the petcock, there are generally two tubes: the "On" tube and the "Reserve" tube. The "On" tube is taller and reaches higher into the tank, and is used when the tank is between one-fourth full and completely full. When the fuel level drops below the height of the "On" tube, the bike will start to stumble. At this point, the rider must switch to the "Reserve" position, which uses the shorter "Reserve" tube until the tank is empty.
The fuel petcock is an old-school version of a fuel gauge. It is essential to the engine performance of a motorcycle. When the bike is not in use or when maintenance is being performed, the valve should be switched to the "Off" position. However, some motorcycles may not have an "Off" position, and others may have a "Prime" position for vacuum-operated petcocks.
The height difference between the "On" and "Reserve" tubes serves a specific purpose. The taller "On" tube allows fuel to flow from the tank to the engine when there is a sufficient amount of fuel in the tank. Once the fuel level drops, the shorter "Reserve" tube comes into play, providing a temporary solution until the tank can be refilled.
The process of switching between the "On" and "Reserve" tubes is straightforward. When the bike starts to stumble, the rider moves the valve to the "Reserve" position. This action starts the fuel flowing through the "Reserve" tube, giving the rider enough time to reach the nearest gas station. It is important to note that the rider should reset their trip odometer to zero when filling up the tank, as this helps in determining how far the bike can go before needing to switch to the "Reserve" position.
Overall, the design of the fuel petcock, including the height difference between the "On" and "Reserve" tubes, ensures a smooth riding experience and helps riders manage their fuel efficiently.
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The petcock is the old-school version of a fuel gauge
The petcock is a valve on a motorcycle's fuel tank. It is also known as a fuel cock or fuel tap. The petcock acts as an old-school fuel gauge, allowing riders to switch between the “on” and “reserve” settings to manage their fuel supply.
Petcocks are generally three-way valves with "On", "Reserve", and "Off" positions. Some petcocks may also have a “Prime” setting for vacuum-operated valves. Inside the fuel tank, there are usually two tubes of different lengths connected to the petcock. The "On" tube is taller and is used when the tank is between one-quarter and completely full. When the fuel level drops below the "On" tube, the bike will start to sputter. At this point, the rider can switch to the "Reserve" setting, which uses a shorter tube to draw fuel until the tank is empty.
Riders can use the petcock as a rudimentary fuel gauge by filling the tank, setting the petcock to "On", and resetting the trip odometer to zero. They can then ride until the bike runs out of fuel, noting the distance travelled on the odometer. This process helps determine how far the bike can go on a full tank and when to switch to the "Reserve" setting.
While modern motorcycles may have fuel level sensors and gauges, older bikes relied on the petcock system for fuel management. Some riders still prefer this simple and reliable method to monitor their fuel usage and avoid running out of gas unexpectedly.
Petcocks are available in various sizes and finishes, such as black, chrome, and brass, making them a customizable part of a motorcycle's fuel system.
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The fuel petcock is also known as the fuel tap switch valve
The fuel petcock, also known as the fuel tap switch valve, is a small shut-off valve used to control the flow of liquid or gas in a motorcycle's fuel tank. It is typically a three-way valve with "On", "Reserve", and "Off" positions, although some bikes may have a "Prime" position instead of "Off". The "On" position allows fuel to flow through a taller tube that reaches higher into the tank when it is between one-fourth full and completely full. When the fuel drops below the level of the "On" tube, the bike will start to stumble, indicating that it is time to switch to the "Reserve" position, which draws fuel from a shorter tube until the tank is empty. The "Off" position is used when the bike is not in use or when the fuel system needs to be drained for maintenance.
The fuel petcock is typically mounted on or near the fuel tank of older motorcycles that lack a fuel gauge. It serves as an old-school version of a fuel gauge, allowing riders to access most of the tank's fuel while leaving a little in reserve. When the bike starts to stumble, riders know that they need to switch to the reserve position and fill up soon.
In addition to motorcycles, petcocks are also used in other applications, such as draining water from diesel fuel water separators in some trucks and as radiator drain valves in automobiles. In the case of German U-boats, petcocks were used to verify combustion in each cylinder of the large MAN six-cylinder diesel engines.
Today, many motorcycles have transitioned to automatic, vacuum-operated petcocks, which may include a "Prime" position. This position bypasses the vacuum operation, allowing fuel to flow to the carburetor without the need for engine turnover. While the fuel petcock plays a crucial role in controlling fuel flow and preventing fuel leakage, it is important to note that modern petcocks are typically ball valves with coarse control, limiting their use primarily to on-off applications.
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Frequently asked questions
A motorcycle fuel tank valve is called a petcock.
The petcock controls the flow of fuel from the tank to the carburetor. It has three settings: "On", "Reserve", and "Off". When the fuel level drops below the "On" tube, the bike will start to stumble, and you need to switch to the "Reserve" setting.
You can buy a motorcycle fuel tank valve online from websites like Walmart, Pingel, and Billetproof Design.
