What is the Work of a Motorcycle Petcock?

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When I bought my first motorcycle and started looking around on forums as to why my motorcycle wouldn’t start I kept reading about a petcock and I was certain it must be a slang term for some part. But sure enough, that’s the actual name of a very important part of every motorcycle fuel system.

What is the work of a petcock? A petcock, also called a fuel tap or fuel val, is a 2- or 3-way valve located in the bottom fuel tank. It directs fuel from the tank to the fuel injectors or carburetors.. Fuel is pulled from the fuel system by gravity or vacuum. The most popular and easiest to use gravity fed systems are generally the least problematic.

When fuel delivery problems to the carburetors occur, it is easy for petcocks to be overlooked. They also fail frequently. I’m going to go into more depth below on how they work, signs that it’s starting to go bad, and how to fix it.

What is the Work of a Motorcycle Petcock?

The petcock can also be turned to ON, OFF or RESERVE positions. If the petcock is in its OFF position, fuel will not flow from the tank to it. This can be used to store the bike between rides. This is how you store your bike between rides.If the carburetor float is not sealed properly, it is helpful to prevent fuel flooding the engine.

If there is an external fuel leaking downstream of the petcock, it can be turned off to prevent it. A petcock can serve as a bit of a theft deterrent, but shouldn’t be relied on for that purpose.

The ON position allows fuel to be drawn freely from the tank to its carburetor. This allows the engine operate. If the engine is difficult to start, make sure that you have the fuel plugged in.

Fuel is flowing from the tank into the carburetor when the RESERVE setting is set, but from a different location. The ON position draws fuel from the bulk of the tank. However, there is a small area at the bottom that allows fuel to be in. “reserve.” This reserve is used for refuelling the motorcycle if the tank runs low.

Another purpose of the RESERVE position, is to empty out the fuel tank. Any water that has accumulated will be found at the lowest point of the tank. Reserving the engine will allow water from the tank to escape and be burned. This will reduce the chance of fuel tank oxidation.

It is very simple to set up a gravity-feed system. Fuel flows freely through gravity when the ON or RESERVE position is set. If the seal is manually turned to OFF, it stops fuel flow from tank.

A vacuum-operated system has an additional valve to the one you would find in a gravity-feed system. The vacuum from the engine operates this additional valve. If there is no vacuum, the spring will hold a small o ring seal in place that stops fuel flow. WheWhen a vacuum is applied, the valve’s diaphragm is pulled inwards which stops the flow of fuel.

Signs Your Petcock May Be Malfunctioning

A petcock can be very simple in theory but there are small parts that can break down over time. Here are some common issues you should be aware of.

First, the petcock may leak. Leakage from the petcock can lead to gas gushing down the sides and onto the ground. A visible drip from the fuel or petcock lines will be common. Leakage of fuel can be a costly waste and pose a danger to your health. There are many reasons why fuel can leak, but we’ll cover the most common ones here.

There are several gaskets and o-rings in the petcock assembly. These gaskets can become worn over time. Sometimes, gasoline can dry out the sealing material and cause it to crack. This causes gasket material to become brittle and makes it ineffective.

The vacuum diaphragm sealings are closely related. These seals are used on fuel systems that have a vacuum-operated petcock. Similar to the gaskets and o-rings, this causation can be observed. The diaphragm material becomes worn out or torn, and it does not hold vacuum. Even though the petcock is turned off, this can lead to fuel leaking through.

An internal leak can also be caused by a failure of the seals. This happens when the seals within the petcock break and allow fuel to leak from the tank to its carburetor. This is when fuel is drained into the cylinder after the carburetor has been flooded. Hydro locking of the engine can result, which could be costly and dangerous.

The gas also seeps into the crankcase and dilutes engine oil. The crankcase is also filled to the limit and the oil/gas mixture can leak onto the ground. This can cause a headache because you need to replace both the petcock and the engine oil.

You may believe your petcock is defective in some cases, but it could also be another problem. One common example is a kinked gasoline line. This can happen if your fuel line has been installed incorrectly or if you have removed the tank and reinstalled it incorrectly. If the fuel line becomes too tight, it can cut off the fuel supply. This could trick you into thinking that the petcock is blocking the fuel.

A fuel screen is installed on some petcocks’ tanks. This screen stops any residue inside the tank from getting into the carburetor, causing problems. These filters will eventually need maintenance. If you neglect to take care of your fuel supply, it may cause fuel shortages or screens that allow debris through.

How to fix a broken petcock

The details of how your bike’s petcock is replaced will vary depending on its make and model. To make sure that your repair goes smoothly, here are some guidelines.

It is important to have access to tools and ventilation as your first order of business. This will involve draining your fuel tank. You’ll need a container to catch it in. You can do this outside or in a garage with ventilation. You can turn the petcock to RESERVE to get all the fuel out.

After the fuel has been drained, it is possible to remove the petcock. If you need to replace gaskets, it will be easier to get it out of your tank. The petcock is usually inserted into the tank’s bottom. Put some masking tape on painted surfaces that you don’t want accidentally scratched by the wrench. Turn the petcock counterclockwise to release the fuel line.

You should now be able to put things back together if you are only replacing the petcock. Make sure the threads on the tank aren’t damaged and carefully install the new petcock. Follow the directions and tighten it. A firm torque will suffice. Don’t over tighten it or it could cause damage.

You will need a screwdriver and a pick to disassemble the petcock. Take care with the small screws and small parts of your assembly. They can easily get lost. A reference is a good idea to have on hand for how the petcock reunites.

Reassemble the tank and replace any seals or gaskets. Some parts from aftermarket may have instructions. Follow these recommendations.

Many petcocks are sealed in the factory with rivets rather than screws. These petcocks cannot be fixed and should be thrown out if they become unwell. The cost of petcocks is not prohibitive. If you own a rivet-style petcock, it’s worth replacing it with a newer one.

It is important to replace the fuel line as well as the hose clamps once the petcock has been reinstalled. Most auto parts and hardware stores sell fuel hoses or clamps. Leakage is common with old fuel lines. Replacing them is relatively easy and inexpensive. Add some fuel to the tank, and then check for leaks. Any other leaks should be addressed before you fire up the engine.

How to Maintain Your Petcock

Every component of a motorcycle will eventually fail. Fuel petcock may wear more quickly than other components because it gets more use. They can also be made cheaply and lead to earlier failure.

Regular inspection is the best way to extend the life expectancy of your petcock. Before you go, make sure to check for any drips or leaks. You should inspect the ground for any gas leaks. Look for cracks and loose fittings in the fuel lines.

It is possible to reduce the use of your petcock if you are concerned about its wear. Vacuum-operated petcocks work even when the vacuum is turned off. You may not need to turn the bike on or off every time you ride if it has this feature. You may opt to only turn the fuel off if the bike is going to sit for a long time or if you’re doing some work on it.

If you are fixing up or restoring a motorcycle, it wouldn’t hurt to replace the petcock. There are many OEM replacements and aftermarket options. You should be wary of low-quality parts. However, there are quality parts available. It will be easier to upgrade this part during a reconstruction than it is later.

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