Symptoms
- Bike runs out of fuel feeling even with gas in the tank
- Fuel leaking from the petcock area onto the engine
- Bike floods or runs rich when petcock is in the wrong position
Likely causes
- CommonPetcock stuck or partially clogged with sediment/varnishOld fuel can leave deposits that partially block the valve, especially after long storage.
- CommonDiaphragm failure on vacuum-operated petcocksA torn internal diaphragm can cause fuel leaking into the intake or a petcock that won't shut off flow.
- PossiblePetcock left in the wrong position (off or reserve when it shouldn't be)Simple as it sounds, this is a common cause of apparent fuel starvation.
- PossibleO-rings or seals dried out and leaking externallyAge-related seal failure can cause a visible fuel leak at the petcock body.
What to do
- Confirm the petcock is in the correct position (usually 'on' or 'reserve', check your manual for symbols).
- Look for fuel dripping from the petcock body or where the fuel line connects, which points to a seal or diaphragm issue.
- If the bike has sat a long time, drain and inspect the fuel for varnish or debris that could be clogging the petcock's internal screen.
- For vacuum-operated petcocks, check that the vacuum line to the carburetor is intact and not cracked, since a bad line can cause the petcock to stay open and flood the engine.
- Clean or rebuild the petcock with a seal kit if it's leaking or sticking, which is a moderate DIY job on most bikes.
- Replace the petcock entirely if it's old, cracked, or a rebuild kit isn't available for your model.
Tools and parts
- Basic hand tools
- Fuel-safe drain pan
Petcock rebuild/seal kit for your bikeSearch: “fuel petcock rebuild kit for [your bike year make model]”
When to call a pro
If you're not comfortable working around the fuel system, have a motorcycle mechanic service or replace the petcock.
Safety
Use caution
Fuel is flammable; work in a well-ventilated area away from any ignition source and be prepared to catch spilled fuel safely.