Petrol Issues (pouring out the tank overflow)

[galaxierog]

Everytime I start the engine petrol pours out of the tank overflow pipe. I thought there was an airlock in the tank but I have opened the tank since and not heard the telltale whoosh of air into the tank when opening the cap. However there is an aftermarket cap on it which probably does not have a valve inside it.

Once the petrol tap is off it does stop (thankfully) but I am worried that it keeps happening and does not stop. Incidentally it pours all over the back tyre too which can't be good can it.

Any ideas?

[KR-1R]

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are you sure its the hose from the tank overflow, or not from one of the carb vent/overflows.

a small piece of dirt or sticky floats may be causing your fuel level not to shut off at the correct level and flowing out through the vents/overflows from the carbs.

a non vented fuel cap is more likely to cause a fuel lock than any overflow - the part of the tank that captures the overflow is around the neck of the cap and between where the cap surround bolts on.
So usually this would only loose fuel when the tank was overfilled to begin with and on the sidestand (angled) to spill.

[galaxierog]

Yep you're right sorry I misunderstood what was happening, it is the overflow from the carb.

Didn't realise it could just be dirt will look at that. and check floats are not sticking.