Smell of petrol / fuel on a Kymco Agility 125 2026

Leak in the fuel system

Safety first: a fuel leak is a major fire risk. Don't ride or start the engine until it's fixed, keep any flame or spark source well away, and work in a properly ventilated space. Diagnosis confirmed: fuel is leaking from the fuel system, causing the level to drop without riding, giving off a fuel smell, and leaving marks on the ground. Common causes: a cracked or poorly clamped fuel line, a hardened carburetor float bowl gasket, a fuel tap that's weeping, a float needle valve that no longer seals (the bowl overflows through the vents), or a loose fitting. The fix: pinpoint exactly where the leak is coming from, with the fuel tap closed, then replace the faulty part or gasket and tighten or replace the clamps. This is an intermediate-level job, manageable for a careful, cautious home mechanic. Risk level: moderate mechanically, but high on the safety side (flammability) -- hence the emphasis on precautions. Cost: a fuel line and clamps cost a few euros; a float bowl gasket / needle valve kit runs roughly 15 to 40 euros; a complete fuel tap around 20 to 70 euros (check pricing). Never ignore a leak, even a small one: a fuel line weeping today can fail tomorrow on a hot engine. If you're unsure of the source, or if the leak is coming from the tank itself, hand the job to a professional. This tool helps you understand what's going on -- it doesn't replace a certified mechanic.

How to make the repair yourself

🟡 Intermediate level: a few basic tools and a bit of method are all you need. Work with a cold engine, take your time, and don't hesitate to stop the moment you're unsure.

1. 1Secure the situation first: turn off the engine, close the fuel tap, keep any flame, cigarette, or spark source well away, and work in a well-ventilated space. Keep a fire extinguisher within reach if possible.
2. 2Pinpoint the exact source of the leak while cold: wipe the area dry, then watch where the fuel reappears. Follow the circuit from the tank to the carburetor: tap, fuel lines, fittings, carburetor float bowl.
3. 3Identify the type of leak: a cracked fuel line or loose clamp; a weeping tap; a hardened float bowl gasket; or a bowl overflowing through its vents (a worn float needle valve that no longer shuts off the level).
4. 4For a fuel line: replace it with a new line rated for fuel, of the correct diameter, and fit new clamps properly tightened. Don't substitute a generic hose not designed for fuel.
5. 5For a leaking bowl gasket: remove the carburetor float bowl (fuel off, container underneath), replace the gasket with a new kit, clean the gasket surfaces, and reassemble without overtightening.
6. 6For an overflowing bowl: check and replace the float needle valve and, if needed, adjust the float height to the manufacturer's spec, so the bowl level shuts off properly and stops overflowing.
7. 7For a weeping tap: replace its gasket or the whole tap (see also the dedicated fix for a vacuum-operated tap if that's the type you have). Check the filter screen while you're at it.
8. 8Reopen the fuel supply and check thoroughly, while cold, for any trace of a leak before starting the engine. Only restart once you're certain it's sealed, then recheck with the engine running, ready to shut it off instantly at the slightest weeping.