Motorcycle Reserve Fuel Switch: The Beginner’s Guide

Reserve Fuel Switch

The reserve fuel switch, also called fuel petcock valve, or simply fuel valve, is used to control the fuel flow from the tank to the engine.

In this guide on motorcycle’s reserve fuel switch, we will understand:

  • What the reserve fuel switch (fuel valve) is used for
  • ‘OFF’, ‘ON’, and ‘RES’ positions of the valve
  • When these valve positions are used
  • How to switch to reserve tank in a motorcycle

Without further ado, lets dive right in.

Reserve Fuel Switch (Fuel Valve)

The reserve fuel switch, also called fuel valve, is a three way valve typically located on the left side of the motorcycle directly under the fuel tank and near the carburetor.

The fuel valve has three switches, namely – ‘OFF’, ‘ON’, and ‘RES’.

While OFF and ON directly refer to the fuel movement from the tank to the carburetor and engine, RES refers to switching to the reserve tank. The fuel flows from the reserve tank to the carburetor and then to the engine.

Reserve tank is not a separate tank from the main fuel tank. Rather it is a part of the main fuel tank, which stores the fuel in reserve to be used only when the main fuel tank runs out of gasoline.

The main use of reserve tank is when the main fuel tank runs out of gas, you can switch to the reserve tank and use the fuel there to go to your nearest gas station.

The RES switch on the fuel valve helps you to use the fuel stored in reserve tank when your main fuel tank has run out of fuel.

Once you switch to RES in the fuel valve, the fuel from the reserve tank is transferred to the carburetor which is then sent to the engine for power generation to the motorcycle.

ON position

At ‘ON’ position in the reserve fuel switch, the fuel is free to move from the main fuel tank to the carburetor and then to the engine.

This is the position you want the reserve fuel switch to be in when you are riding your motorcycle.

Reserve Fuel Switch - ON

Switching ON the fuel valve is basically allowing free flow of the fuel from the fuel tank to go to the engine through the carburetor.

The fuel is transferred from the main tank to the carburetor wherein it will be mixed with air to form the air-fuel mixture.

This air-fuel mixture is transferred from the carburetor to the engine combustion chamber. Within in the combustion chamber, the air-fuel is compressed and burnt with the help of spark plug to generate power in the engine. The generated power is used to move the motorcycle.

When to use ON: You need to keep the reserve fuel switch to ON whenever you are riding the motorcycle. Basically, ON means the usage fuel from the main tank to move the motorcycle.

OFF position

At ‘OFF’ position in the reserve fuel switch, the fuel does not flow from the fuel tank to the carburetor and hence to the engine.

The fuel flow into the engine is cut-off when you turn the fuel valve to OFF position.

Reserve Fuel Switch - OFF

Usually, one keeps the reserve fuel switch position to OFF when they are not going riding the bike for a period of time.

Few bike riders even switch the valve OFF every time they park the motorcycle.

While this kind of aggressive switching OFF is not required, it is advised to turn the valve OFF if you are not going to use the motorcycle for the next two to three days.

Switching the fuel valve OFF basically means you are not allowing the fuel to flow outside the fuel tank.

As a result, there is no fuel coming into the carburetor and hence, no fuel entry into the engine combustion chamber.

Even if you try to start the motorcycle, the bike won’t start since the engine is not receiving any fuel to generate power.

When to use OFF: By switching the valve OFF, you will be cutting off the flow of fuel from the tank. Use the OFF position when you are not using the motorcycle. Especially if you are not going to ride your bike for the next few days.

RES position

At ‘RES’ position in the reserve fuel switch, the fuel from the reserve tank is free to move to the carburetor and then to the engine.

This is the position you want the reserve fuel switch to be in when you have run out of fuel in the main tank.

Reserve Fuel Switch - RES

The RES switch is a backup option used to access fuel in case the gasoline in the main fuel tank runs out.

One important aspect to understand here is, the reserve tank is not a separate tank. Rather, it is a part of the main fuel tank. However, the ON position on the reserve fuel switch will not have access to the fuel in the reserve tank.

Only when you switch the fuel petcock valve to RES position, will the fuel from the reserve tank flow to the carburetor.

However, the amount of fuel in the reserve tank will be very low. The reserve tank fuel should be used to get to the nearest gas station and refill your main fuel tank.

When to use RES: The RES position reserve fuel switch is used when the main fuel tank is emptied out. You need the reserve tank fuel to get your motorcycle moving so that you can reach the nearest gas station to refill the tank with fuel.

Reserve Fuel Switch Positions

Here is the summarized fuel flow in the motorcycle for each of the reserve switch positions.

PositionFuel Flow
ONFuel flows from the main tank to the carburetor.
OFFFuel flow is cut-off. No fuel flows to the carburetor.
RESFuel flows from the reserve tank to the carburetor.

How To Switch To Reserve Tank In Motorcycle

If you have run out of gas in your motorcycle fuel tank and are stranded in the middle of a road, the reserve tank is going to be your saviour at this time.

Switching to reserve tank will provide additional fuel flow to the engine, which you can leverage to drive to the nearest gas station and refill your main fuel tank.

All you need to do is turn the fuel petcock valve located on the left side of your motorcycle near the carburetor, from ON position to RES position.

Currently, the fuel valve will be at ‘ON’ position when you run out of gasoline in the main tank.

Now, turn the valve 180 degrees to switch its position to ‘RES’.

Once you have switched to the reserve position in the fuel valve, the fuel from the reserve tank will starting flowing into the engine to generate power.

You can start the motorcycle now and ride to the nearest gas station to refill the main fuel tank.

Related questions

Can you run the motorcycle on reserve all the time? You can run the motorcycle on reserve all the time. However, once the fuel is emptied out you won’t have a safety net to fall back since the fuel in the reserve tank is also emptied out. You won’t get to know when the main fuel tank was emptied earlier.

How much distance can you travel in reserve? Sincethe reserve tank is to be used only as a backup option to travel to the nearest gas station, the capacity of reserve tank will be low. Usually, the reserve tank can hold half to one litre of gasoline in most bikes. You can travel an approximate distance of 20 to 30 miles based on your motorcycle mileage.

Do all motorcycles have reserve tank? Not all motorcycles have reserve tanks. Most modern motorcycles with fuel injection do not contain reserve tanks in them. However, all carburetted motorcycles have reserve tanks.