Tank Breather ??

[seth]

Ok try this fill your tank full while in a cool shaded place then move it into the sun and cover the fuel cap with very soapy water you'll see if the tank vents out by the bubbles made that will at least let you know have the story.
Sorry I can't offer anything else as advice .

[Kiwifruit]

It has me baffled too. At least l seem to have the fix for it when it does happen. Done 1000kms on her this week, 999.5kms of them without issue.

[gsxbarmy]

So the hose that tucks in behind the swingarm pivot I thought was a breather is in fact a water drain and fuel overfill / spill drain hose and not a breather hose at all.

There are 2 hoses that tuck in there Colin, one from the air box (which is a drain and has a plug on the end), the other is the tank overflow/breather pipe.