Fuel & Running Costs
Fuel Tap on a Manual Bike: What ON, RES and OFF Mean Before You Assume the Tank Is Empty
About 7 minutes to read
A geared bike coughs, surges and cuts out on a quiet road while the dashboard still seems to show some fuel. Before deciding the tank is empty, a renter has one more thing to look at: a small lever below the tank, on bikes that carry one, that decides which fuel supply reaches the engine. This article explains what the positions marked ON, RES and OFF can mean, how to learn at handover whether the bike has such a tap, and what to do on the road if the bike falters. It is written for someone who has not met a fuel tap before. The bike’s owner’s manual and the shop’s instructions come first, so the article gives no capacities, requirements or model figures.
Does the bike carry a fuel tap at all?
Not all rental bikes have one. Some geared bikes deliver fuel through an electric pump and have no lever to turn, while others carry a small tap under the tank; the clutch lever alone does not tell you which kind you have. The manual shows the layout for the exact model; if there is no manual to hand, ask the shop. When a tap is fitted, look for:
- a short lever or knob low on the tank, close to where the fuel line leaves it, on either side of the bike;
- letters, arrows or symbols moulded into the plastic or stamped on a small plate around it;
- a lever that points at one marking, or a knob that clicks from one position to the next.
The tap may sit partly hidden by a side cover or the footrest area, so look from the side with the bike upright on its stand. Do not remove a panel to find it.
What ON, RES and OFF mean
The labels are shorthand for which fuel supply the engine can reach. The table gives the general meaning, and the diagram in the manual for this bike settles any difference.
| Label | General meaning | What to check on the bike |
|---|---|---|
| ON | Fuel flows from the main supply; this is the position meant for riding | Which marking the lever points at, shown in a photo |
| RES | Reserve: opens a lower outlet, so the engine can draw on a limited extra amount once the main supply is used up | Whether the gauge reads low, and how the shop describes using this position |
| OFF | The tap is shut and no fuel passes to the engine | Whether the manual asks for this position while parked |
| Other labels | Some taps carry a further position, or use arrows in place of letters | The manual’s diagram for this exact model |
Treat RES as a prompt to refuel, not as spare capacity to plan around. Once the tank is filled, move the lever back to the riding position the manual names, which is ON on a tap labelled this way. A lever left on RES means the next shortage arrives without any notice.
Why a tank with petrol in it can act empty
A cough or cut-out can come from several situations; the table pairs what you see with what it may mean.
| What you see | What it may mean | Sensible next step |
|---|---|---|
| Lever at OFF, though the tank holds petrol | The engine may start, run briefly on what already lies beyond the tap, then cough and die | Stop, switch off, and return the lever to the riding position the shop demonstrated |
| Lever at ON, gauge low or absent | The main supply may be used up | Stop and switch off; RES only as the manual or shop has shown, then refuel |
| Lever at RES, the engine coughing again | The reserve is running down as well | Pull over safely and treat the bike as out of fuel |
| Lever at ON, gauge shows fuel, engine still cuts out | The tap may not be the cause, and a different fault may be present | Leave everything as found, photograph it, and call the shop |
On a bike with no fuel gauge, a cough may be the first sign that the main supply is gone. A gauge can mislead as well; Reading a Rental Bike Fuel Gauge: Plan Range Without Guessing covers reading one and planning range without guessing.
Learn the tap while the bike is parked
Handover is the calm moment to learn this, with the engine off. Work through these steps:
- Ask whether the bike has a tap fitted, and have the lever pointed out.
- Look at the marking beside each position, and have each one demonstrated with the engine off.
- Ask which position is meant for riding and which, if any, for parking.
- Before riding off, check that the lever is back at the riding position after the demonstrations, then photograph it with its labels in view, so the starting position is on record.
- Note whether the dashboard has a fuel gauge.
Short answers on renting sit in the rental FAQ; a bike-specific question like this one belongs with the shop.
What not to do with a fuel tap
- Do not force a stiff lever or reach for a tool; a lever that will not move is something to report.
- Do not turn the lever while the bike is rolling. Stop and switch off first.
- Do not ride on RES to learn how far the bike will go.
- Do not rock the bike or tip it over to push the last petrol toward the outlet.
- Do not use a lighter, a match or any flame to look into the tank, and do not smoke near the bike.
- Do not remove panels, pull fuel lines or disconnect hoses to trace a fault.
If the bike coughs and cuts out on the road
- Ease off the throttle smoothly, signal, and steer toward a safe stopping place while the bike still responds. On a bike with a clutch lever, pull the clutch lever in as the engine falters so the bike coasts without jerking, and use both brakes progressively.
- Once stopped, switch off the engine and the ignition, and put the bike on its stand on firm, level ground, clear of traffic.
- With the bike at rest, look at where the lever points and compare it with your handover photo. A gauge may show nothing while the ignition is off, so if the dashboard has one, switch the ignition on briefly with the engine still off, read it, then switch it off again. Skip that if you smell petrol or see liquid, and go straight to the last step. Touch nothing else.
- If the lever points at OFF or between two markings, put it back where the shop said it belongs for riding. If it sits at ON, the gauge reads low or is absent, and RES was demonstrated at handover, you may move it to RES as shown, restart gently and ride straight to a pump; if the engine coughs again on the way, pull over safely and call the shop. If RES was not shown, leave the lever alone and call the shop.
- If the lever is in its proper place and the gauge shows fuel, or the engine will not stay running after you correct the lever, stop trying. Photograph the dashboard and the lever, note the place and the time, and call the shop.
- If you smell petrol or see liquid dripping, keep people and flames away, leave the engine off and phone the shop. If you see smoke or flames, or someone is hurt, call for emergency help first.
When the tank is truly dry, Out of Fuel in Hanoi: Stop Safely, Refuel With the Right Petrol and Tell the Shop covers the stop, the refill and the call.
Questions to ask the shop about the fuel tap
- Does this bike have a fuel tap, and can each marked position be demonstrated with the engine off?
- Which position suits riding and which suits parking, and what should be done if the engine cuts out while the gauge still shows fuel?
Thuê xe máy Nguyễn Hà is open 09:00–21:00 daily at Ngõ 5 Nguyễn Văn Cừ, Bồ Đề, Long Biên, Hà Nội (near Gia Lâm bus station). Phone: 0334 699 969.