A Complete Guide To Motorcycle Reserve Fuel Tank (RES)

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Motorcycle riders who ride modern fuel injection motorcycles may wonder about the motorcycle reserve fuel switch.

But motorcycle riders with a a carburetor engine motorcycle understand the importance of a “reserve fuel switch”.

The reason is a motorcycle with carburetor engines normally has a reserve fuel tank and a reserve fuel switch.

This article will tell you all you need to know about the reserve fuel switch.

What is the Reserve Fuel Switch?

The reserve fuel switch (also called a petcock) is a simple 3-way valve used for controlling the flow of gasoline from the tank into the carburetor bowls.

The total capacity of a motorcycle’s fuel tank is divided into two parts:

  • One part is the main tank.
  • The other part is the reserve tank.

Note that there is only one fuel tank, but a part of the fuel tank functions as a reserve fuel tank through different sized valves.

The reserve fuel switch has three positions: (i) OFF, (ii) ON, and (iii) RES (reserve).

When the gasoline in the main tank is completely used, you can turn the fuel switch to the RES position and the gasoline in the reserve fuel tank flows into the carburetor and you can ride to the nearest gas station to fill the fuel tank.

Using the Motorcycle Reserve Fuel Switch

You are riding your motorcycle fast on a freeway and suddenly you feel your motorcycle engine losing its power.

If you are an experienced rider and riding a motorcycle with carbs, your hand goes immediately to the reserve fuel switch, and turn the reserve fuel switch to the RES (reserve) position is all that takes to get the power back into your motorcycle engine.

The reserve fuel switch is an important feature of the carburetted engine motorcycles.

However, if you are a new rider, you may take some time to understand and become accustomed to the reserve fuel switch.

The reserve fuel switch or the fuel petcock valve is a three-way valve and it is normally located on the left side of the motorcycle (below the fuel tank and near the carburetor).

The reserve fuel switch has three positions:

  • ON.
  • OFF.
  • RES (reserve).
Reserve Fuel Tank

The “RES” refers to the reserve tank that is essentially a lower part of the main fuel tank.

Your motorcycle fuel tank is divided into two imaginary parts, one part is the main tank and the other part is the reserve tank.

The reserve tank has sufficient gasoline to keep you riding till you reach the nearest gas station.

The gasoline in the reserve tank is a backup to help you when the fuel in the main tank is exhausted.

Let us understand what happens when you turn the reserve fuel switch to OFF, ON, or RES (reserve) positions.

Petcock Position OFF

Turning the reserve fuel switch to the “OFF” position: When you turn the reserve fuel switch to the “OFF” position, the flow of gasoline from the main and reserve fuel tank will stop and there is no flow of gasoline into the carburetor.

Most riders turn the reserve fuel switch to the “OFF” position when they are parking the motorcycle for a few days.

But some riders turn the fuel switch to the “OFF” position even when they park the motorcycle for the night and the reason is they want to avoid flooding the carburetor with gasoline.

Petcock Position ON

Turning the reserve fuel switch to the “ON” position: When you turn the reserve fuel switch to the “ON” position, the gasoline flows from the main fuel tank into the carburetor until the quantity of gasoline comes down to the reserved capacity.

As soon as the gasoline quantity reaches the reserved capacity the flow of gasoline into the carburetor stops.

The gasoline stored in the carburetor allows you to ride your motorcycle for a short time and then the engine stops.

Petcock Position RES

Turning the reserve fuel switch to the “RES (reserve)” position: When the quantity of the gasoline in the main fuel tank is exhausted, the gasoline in the reserve fuel tank comes to your rescue.

To turn on the reserve fuel switch all you have to do is turn the switch by 180˚ to the RES (reserve) position.

When you turn the reserve fuel switch to the “RES” position the gasoline from the reserve fuel tank flows into the carburetor and the engine starts once again.

The gasoline in the reserve fuel tank will be sufficient to take you safely to the nearest gas station and you can fill the fuel tank again.

Do not forget to turn the reserve fuel switch to the “ON” position before you ride the motorcycle.

Do all motorcycles have a reserve fuel switch?

No, a reserve fuel switch is normally a feature associated only with motorcycles fitted with carburetors.

All carburetor engine motorcycles normally have a reserve fuel tank and reserve fuel switch.

Modern motorcycles with fuel injection do not have a reserve fuel switch, but they have a fuel gauge that displays the fuel position in the tank.

What happens if I run my motorcycle always with the reserve fuel switch on?

Nothing happens to the motorcycle.

The motorcycle runs as long as there is gasoline in the main and reserve fuel tank and when both the main and reserve fuel tank becomes empty the motorcycle stops.

Running on RES at all times may make it more difficult to gauge how much gas you have left in the tank.

You may end up pushing the motorcycle to the nearest gas station.

What is the capacity of the reserve fuel tank?

The capacity of the reserve fuel tank varries from motorcycle to motorcycle, but it is more than sufficient for you to reach the nearest gas station (15 to 25 miles).

You can look into the owner’s manual to know the exact quantity of gasoline in your motorcycle reserve tank.

Can I ride my motorcycle when the reserve fuel switch is in the “OFF” position?

When you turn the reserve fuel switch to the “OFF” position gasoline cannot flow from the main or reserve fuel tank into the carburetor.

If you attempt to ride the motorcycle in this position, the engine runs for a while using the leftover fuel in the carburetors, and then it stops.

Tips for New Riders

If you have turned the reserve fuel switch to the “OFF” position when the motorcycle was parked, do not forget to turn the switch to the “ON” position when you start riding your motorcycle again.

Turn the reserve fuel switch to the “OFF” position when you are parking.

Always keep the reserve fuel switch in the “ON” position when you ride your motorcycle. By doing this you will know when the gasoline in the main fuel tank is completely consumed and you can ride to the nearest gas station using the fuel from the reserve fuel tank. Once you fill the fuel tank, do not forget to turn the reserve fuel switch to the “ON” position.

If you are a new rider, refer to your motorcycle user’s manual and know the quantity of the gasoline in the reserve fuel tank (it can be 0.5 gallons or more).

Do not ride your motorcycle with the fuel switch in RES position when the main tank is full since you are removing the safety of the reserve tank by doing this.

The reserve fuel switch is an important feature of a carburetor engine motorcycle, and hopefully, this article has given you all the information and made you a little wiser.

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