Petrol Leak At Breather

[ianp]

Hi All,
My 2009 Corsaro Veloce has sprung a petrol leak after refilling on its first proper run out this year. It is coming from around the breather outlet on the bottom of the tank. It was a constant weep over several days until I drained the tank (yes, I can still taste petrol!), my concern is even though the o-ring has perished should petrol be there to leak in the first place? The photo shows the underside of the tank and the two breather outlets.

[nickst4]

It's not just overfilling with cold fuel that then sits over a hot engine, expands and finds its way down the overflow? Been there, done that. Might it even be possible for it to get into syphon mode?

Nick

[eddydog]

There are by-pass channels in the filler neck. If the tank is filled to the very top, then when the motorcycle is tilted, a possible overflow of fuel into these drain channels and further into the pipe. Yes. this is bad, since the drain pipes have an outlet near the exhaust manifold of the rear cylinder. or if you have lifted the fuel tank and these tubes are bent from the back bottom of the tank. You need to carefully examine everything to eliminate these possible excesses.
And I see in your photos that these plastic drain pipes are broken off. there should be a shaped exit from these holes. a rubber tube is put on them, which brings gasoline leaks to the very bottom of the engine, below the exhaust manifold. You need to fix this urgently, as possible leaks of gasoline can lead to a fire on the hot rear exhaust manifold.
It is not clear from your photo which side these holes are from. The pipe with a y-shaped plastic outlet should be located on the right side of the motorcycle, in the lower right side of the fuel tank.

[ianp]

I think you've misunderstood, the tank hasn't been overfilled or overflowed, when I removed the breather pipes they were dry. The leak is on the bottom of the tank and the photo shows the outlets with the pipes and inserts removed. My concern was that even though the o-rings on the pipe inserts had perished and allowed petrol to leak, it shouldn't be there to leak. This photo shows the expansion breather pipe in place with the leaking overflow pipe and insert removed.

Update - I have fitted new o-rings, refilled the tank and no leaks so far.