You smell petrol around the bike: when it is parked, after you stop, or while you ride. A faint smell for a moment after filling up is normal. A strong or lasting smell means fuel liquid or vapour is escaping, or the engine is burning too much fuel. Liquid fuel near hot parts is a fire risk, so find the source first.
Is it safe to ride?
Not until you have found the source. If you see any wet fuel, treat it as a leak and see Fuel is leaking or dripping. A smell only from the exhaust is less urgent but should be fixed soon.
Quick checks first
- Is anything wet: hoses, tap, carburettor, tank, ground?
- Where is the smell strongest: the tank and cap, the carburettor or throttle body, or the exhaust?
- Does it smell more after the bike has been parked on its side stand?
- Is the choke left on?
- Is the oil level rising, or does the oil smell of petrol?
Diagnose it step by step
1Is any fuel visible, wet or dripping?
- Yes: go to Fuel is leaking or dripping.
- No: go to step 2.
2Is the smell strongest at the exhaust, with black smoke or a sooty plug?
- Yes: the engine is running rich. Check the choke and air filter, then see Engine runs rich.
- No: go to step 3.
3Is the smell strongest around the carburettor, especially after parking?
- The float needle may be letting fuel past into the intake or out of the overflow while parked. Look for a damp overflow pipe end and a damp air box. Check the carburettor float and needle valve. Turn the fuel tap OFF when parking.
- Check the engine oil: if it smells of petrol, see Oil smells of petrol.
- No: go to step 4.
4Is the smell strongest around the tank and filler cap?
- Check the cap seal and the vent: Clean and lubricate the fuel cap. Do not fill above the filler neck.
- On bikes with a vapour (EVAP) system, fuel vapour goes from the tank through a rollover valve to a charcoal canister. A cracked hose or a failed valve releases vapour. The K-Light 125 has this system; its manual says a damaged rollover valve is replaced. Check the fuel tank vent and its hoses.
- No: go to step 5.
5Fuel-injected: is the smell near the throttle body or the pump on the tank?
- A slow seep at the injector O-ring or the pump seal may evaporate before it drips. Key OFF and take it to a workshop: Check the fuel injector and Check the fuel pump.
6. Still smells, nothing found? With the tap ON, wrap clean paper around each hose joint for ten minutes and check for damp spots: Check the fuel tap, lines and flow.
Causes, most likely first
| Cause | How to confirm | Fix |
|---|---|---|
| Small leak at a hose or tap | Damp paper at a joint | Tap and lines |
| Rich running or choke on | Smell at exhaust, black smoke | Choke check |
| Float needle passing fuel when parked | Damp overflow, smells after parking | Float check |
| Cap seal, overfilling or vent hose | Smell at the cap | Fuel cap |
| Vapour hose or rollover valve | Cracked hose, failed valve | Tank vent |
| Injector or pump seal seep (injection) | Smell near throttle body or pump | Injector check |