If someone asked me a few years ago about motorcycle petcock, I would think that this word is some kind of “a casual term”. Later on, I realized that I was wrong and, as a matter of fact, that a petcock is a part of a motorcycle’s fuel system. Since it has a significant role in the fuel system, it would be smart for us to know how to deal with possible issues and is even possible for us to fix them.
So how to fix a motorcycle petcock? Remove the petcock from the tank by detaching the fuel line and rotating your petcock counterclockwise. If you plan to repair the old petcock, you need to take it apart; otherwise, replace the old petcock with the new one. Return the petcock to the tank.
In this article, we will explain how petcock works, how to fix them, and how to recognize the signs that signal you that there is something wrong with them. Therefore stay with us because this article will bring you everything you need to know about the petcock.
Table of Contents
How to Repair a Petcock
Step 1: Empty the Fuel Tank
Empty the fuel tank and sip the fuel in a clean container from which you will put the fuel back once the job is done.
Note: Put the petcock in the RESERVE position to drain all the fuel from the tank.
Step 2: Remove the Petcock
Remove the petcock. Most of the time, the petcock is situated at the bottom of your motorcycle tank. When petcock is separated from the tank, working on it is easier, especially if you need to replace gaskets.
Tip: Use painter’s tape and place it on surfaces to prevent scratching (nothing serious can happen even if you scratch it, it will only visually disrupt). Detach the fuel line and take the petcock out.
Step 3: Install the Petcock
Check the threads on the tank. Don’t tighten it too much. Install the new petcock and tighten it; a solid torque will be enough.
If you want to fix the old petcock, get to the next step.
Step 4: Take the Petcock Apart
Use a pick and screwdrivers and take the petcock apart. Assemble the petcock in reverse order. Refer to your motorcycle manual if you have trouble doing so.
Step 5: Replace Seals and Gaskets
Change seals or gaskets and reassemble the petcock. Once you have reassembled the petcock, return it to the tank.
Note: Some petcocks are factory sealed using rivets instead of screws. These petcocks cannot be repaired, and you should throw them away if they are broken. If you have a rivet-type petcock, consider buying a new one since they are not expensive.
Replace the hose clamps and the fuel line after reinstalling the petcock. Old fuel lines can leak, and changing them would be wise since it is not expensive. Once you have done that, fill the tank with some gas and look for any leaks. If you spot any leaking, fix them. Your engine is ready to start once you have done all the previous steps.
How to Recognize a Faulty Petcock?
A petcock may look easy to understand, but it consists of pieces that can easily wear out. You need to be prepared for some of the possible problems.
The petcock contains one or more o-rings or gaskets, which can wear out. The seal becomes ineffective and lets the fuel leak if the gasket material gets displaced. The gasoline causes the sealing material to dry, which eventually crumble.
The vacuum diaphragm seals are closely related and placed on vacuum-operated petcock fuel systems. There is no vacuum when the diaphragm material gets worn. This issue can make fuel leaking from the petcock even if it is turned OFF.
The petcock leakage: you will see fuel lines coming from the petcock. A leaking petcock causes fuel to leak, which can be hazardous for the environment. Some reasons may lead to petcock leaking.
An internal leak presents another problem. This issue happens when the seals inside the petcock are faulty, and the fuel gets out of the tank to the carburetor. Once the carburetor gets filled, fuel runs into the cylinder. This increases the risk of the engine getting hydro-locked, which is at the same time a big and expensive problem.
This also leads to gas leaking into the crankcase and rarefying the engine oil while at the same moment overfilling the crankcase, causing the oil-gas mixture to leak outside and hit the ground. To deal with this problem, you have to replace the petcock and the engine oil as well.
Note: In some cases, you could think that there is something wrong with the petcock, while the problem could be somewhere else.
A bent fuel line: This situation happens when the fuel line is not installed correctly or when the gas tank has been removed and placed back incorrectly. When the fuel line gets clogged, it suffocates the fuel supply, leading you to think that there may be something wrong with the petcock and that the petcock is blocking the fuel.
How to Increase Your Petcock Lifespan?
The fuel petcock is one of the motorcycle parts that could wear out because it gets used a lot. Since most riders look for cheaper parts, this is not always a smart thing to do because these parts can be made from poor quality material leading to an early failure.
Doing frequent examinations is by far the best action that you can do to extend your petcock’s life. Inspect if there are any signs of leaking or dripping before every ride.
Vacuum-operated petcocks function even when in the OFF position for safety measures. If your motorcycle has a vacuum-operated petcock, you don’t need to turn it ON and OFF before and after every ride. Turn it OFF only if you don’t plan to drive for a longer period or in case you are doing something on the motorcycle.
The Working Principle Behind the Petcock
A petcock is a two or three-way valve used to control the fuel flow placed on the bottom of the motorcycle’s fuel tank. It is a valve controlled by a handle (most modern petcocks are ball valves). It works by sending fuel to the fuel injectors or carburetors out of the tank. Vacuum or gravity pulls the fuel from the fuel system.
When there are problems related to fuel delivery to the carburetors, the petcock is usually overlooked, and this shouldn’t happen because they can malfunction oftentimes.
There are three petcock positions: ON, OFF, and RESERVE.
ON position lets the fuel flow from the tank to the carburetor, and by doing so, the engine is ready to start. If the engine has some kind of a starting problem, take a look and see if the fuel is turned ON because I have witnessed that there were cases where riders left the petcock in the OFF position and then wondered why their motorcycle won’t start.
When in the ON position, the fuel flows from the bigger part of the tank. A small segment on the bottom of the tank keeps a small amount of fuel in “RESERVE”. When placed in RESERVE position, fuel also runs from the tank to the carburetor, but it runs out of a different tank part. The reserve compartment allows the motorcycle to get to the nearest gas station for refuel if the bike runs out of fuel.
The RESERVE position is also used to clean out the fuel tank. If there is any water gathered, it can be found on the lowest part of the tank. The water will run from the tank and evaporate in the engine by switching your motorcycle to the RESERVE position. With that being done, it will decrease possible oxidation that can happen in the fuel tank.
The OFF position keeps the fuel in the tank so it doesn’t flow to the carburetor. This position is mainly used when the motorcycle is stored, or some riders even use it between rides. This position is helpful because it keeps fuel in the tank, and the fuel does not flow to the engine. This is very important if the carburetor float is not sealed correctly.
Note: If you notice an external fuel leak coming out of the petcock, switching it OFF will stop the leaking. By doing so, you will prevent fuel from dripping on the ground ( this way, you are not endangering the environment, and you are saving your money)
A gravity-feed system is quite simple. The ON and RESERVE positions allow the fuel to run freely because of the gravity, while the OFF position prevents fuel from running out of the tank.
A vacuum-operated system has another extra valve added which operates by the engines vacuum. If there is no vacuum, a spring keeps a tiny o-ring seal that prevents fuel from running.
The presence of a vacuum enables the fuel to flow.
Here you can watch a video on How to rebuild a leaking petcock:
Conclusion
The petcock is a significant segment of a motorcycle’s fuel system; therefore, it is crucial to take care of it and ensure its proper functionality. It is responsible for fuel delivery, and because of that, we need to maintain it and lower the chance of any malfunction that could happen because if it does happen, it could get our motorcycle out of use for some time.
We hope you liked our petcock article and that it has helped you fix your problems. Make sure to read our other articles regarding dealing with motorcycle problems and fixing the same.