Riders often feel that a bike "drinks fuel", but feelings and fuel gauges are not accurate. A fill-to-fill test gives a real number you can compare before and after a repair, or between bikes. It also shows whether the change is small (riding style, traffic, load) or large (a mechanical fault).
Safety
- Do not watch the trip meter or write notes while riding. Record at the pump with the bike stopped.
- Fill only to the bottom of the filler neck. Overfilling spills fuel onto the hot engine and blocks the vent.
Steps
- Fill the tank at a fuel station until the fuel just reaches the bottom of the filler neck, or the same mark you will use every time. Use the same pump if you can, with the bike upright on its stand.
- Reset the trip meter to zero, or write down the odometer reading.
- Ride as you normally do. Do not change your style for the test. Ride at least most of a tank.
- Fill again to exactly the same level. Write down the litres added and the distance from the trip meter.
- Work out the result: - km per litre = distance (km) ÷ litres added. Example: 180 km ÷ 4.0 L = 45 km/L. - litres per 100 km = litres added ÷ distance (km) × 100. Example: 4.0 L ÷ 180 km × 100 = 2.2 L/100 km.
- Repeat for two or three tanks and take the average. One tank is not enough; filling level and traffic change the result.
- Write down the conditions: traffic, passenger or load, rain, hills, tyre pressure, fuel grade.
How to read the result
- Compare with your own earlier figures for the same bike and the same kind of riding, or with other bikes of the same model used the same way.
- A change of a few percent is normal: weather, traffic and fuel vary.
- A large, steady rise with no change in riding is a fault. Go to Uses more fuel than normal. The K-Light 125 manual's checklist starts with riding style, load and gear, then dragging wheels, tyre pressure, fuel leaks, mixture (air filter) and idle speed.
- Check fuel quality too: the K-Light 125 manual specifies good unleaded 92 or 95 grade.
Check your work
- Repeat the test after a repair. The figure should return close to your earlier normal.