Tank vacuum - want to fix it once and for all..

[maggot]

So I've been having a load of trouble with my breather tube being blocked or clogged or whatever, after an accidental overfill by a mate. I've been getting a vacuum developing in my tank, starving my carbs and creating engine failure.
I've had the tank off at least three times, checking lines, draining petrol, refilling, giving it a bit of a shake, redoing the breather tube etc etc.
This last time, I thought I had it sorted. Until I wandered down to the bike today, and heard a squealing from the tank. So I popped the lid and it came off with a solid sounding PHWOP.

I'm getting pretty sick the problem, so I wanna deal with it once and for all. What should I do? I'm already stripping the bike down tomorrow to clean out the carbs, making a day of it. So what should I be doing to fix the tank problem?

I'm getting pretty sick of riding round with the tank open all the time..

Cheers in advance..

[Max Preload]

You're not confusing the filler neck drain with a breather, are you?

[maggot]

Wouldn't have a clue really.

[Voltaire]

Had this with my tank. there were two tubes under the tank going into one. The first is from the lower filler area and drains off spilt fuel, the other lets the air in as fuel is used.
Whats probably happening is the vent hole in the filler is either blocked or the rubber seal between the filler and the hinged flap O ring seal is covering the vent hole.
...or when you fit the tank its kinking the tube.
Mine was mainly down to the seal between the filler and the hinged lid collapsing and causing the vent to block.
Your carbs are proabably ok, blow thru all the tank hoses first.

[Max Preload]

I'd say you've just been wasting time (well, not a real waste, but it's not going to solve THIS particular problem) cleaning the filler neck drain which is there solely to drain rainwater etc. from around the filler cap so it doesn't pool and when you open it flow into the tank. I would expect that an RGV150 would vent through the cap.