Fuel leak from tank?

Looking for a few pointers.

I brimmed my tank just the other day: 1st time I've done it that full. Just cleaning the bike after my trackday and noticed there is a fuel leak from the little fitting at the right hand lower corner. Looks like its a breather or something and should have a pipe coming from it. Got my fingers in and it feels secure enough.

Any ideas how this is connected and what its linked to? There was a slight fuel mark on the floor before I left for the track day. Went through 20 of fuel there and tank was only filled to 2/3 max at a time. So its not just fuel that's been lying about from being overfilled, its def leaking albeit very slightly.

viewtopic.php?f=18&t=17444&p=203689#p203689

Front is an overflow and rear is a vent

That's the thread I was looking for.

It's the rear that's leaking on mine though, on the right hand side. Just weeping about that L shaped nipple area. There's no drain hose connected to it.

I should prob stop reading the forum when I'm shattered, but not sure what the cure is here.

As per other thread, it it worth blowing air up that L shaped bracket and see if there's an air leak? Assume there will be a small leak from the top around the filler cap area. Not quite sure why it would then leak out fuel when the tank is only sitting with 1/4 fuel in it. Surely it would just give out vapour on expansion at worst?

This will prob all make sense in the morning

I've got the tank off mine just now.

FYI - There two of these L shaped connectors Front Left (With over flow tube attached) and the one you mentioned with no tube at the Rear Right.

It is possible to rotate these because there are small rubber gasket/washer/seal between the tank and the L connector. I suppose you could have a leak from the seal assuming this continues to weep. Suppose if you monitor it you'll find out if it's a one off or a leaky seal.

It's v. easy to lift the remove tank and i'd guess swap the seal if req'd

Investigated tonight.

It's leaking from the rear L shaped nipple. Took it off and blew air up it to find it is linked to the righthand drain under the filler cap. Removed the cap assembly and found there was a bit of plastic that seals the drain pipe to the inside that has a poor seal just inside the tank. So the fuel was pressurising and beiing blown out here. Plugged bottom hole, put a pipe in the top and blew through and you can hear the small air leak. Sealed it up with Quicksteel Putty, leak sorted.

The pic is taken looking back towards the seat. You can see the little cracked/open area just inside the tank at the pipe, this is where it was leaking out to the drain pipe.

I had the same problem on my carbon tank! leaked out the front overflow when full to the brim same bad joint you described!
had to use epoxy metel glue as the putty was not compatible for use in petrol?
I was told it would contaminate the fuel?
hope you checked this out !
ps mine has been sound since
cheers

Yep, safe to use in petrol.

It's not worked anyway. Came home tonight and checked and its still leaking. Feels like its been a bubble in the molding when the tanks been made. Front drain is moulded nice and smooth where it joins internally under the filler area.. Rear is all bitty and feels like there has been a little air bubble in the plastics that's burst open.

From blowing through it seems that the drain is only there to get rid of spilt fuel when filling. It's also got the front drain for that so the rear could just be blocked up I think. Was thinking about filling it with epoxy down the tube to just do away with it totally.

If you do, as I understand it, the tank will not be vented and a partial vacuum will result unless you modify the cap.

Cheers. I'll look into that. Might be worth modifying the cap.