I just wanted to relay a sitution that happened to me last week on a road trip. For no apparent reason my speedie died on me. I was happilly riding along and all of a sudden, sput sput kapooth, blat, sput, brut, blahhhhhhhh. dit, blooth (like my noises

) and then she conked out.
Because of this place and with my newly gained experience with carbs etc, I thought it may have been the fuel tank over flow tube.
So I laid down next to my bike and tried to blow and suck the over flow tube. Well I couldn't get any air through which was what I wanted.
Took off the tank and it appeared the tube was pinched against the frame. Unfortunately for me, she started but again about 10k along sput sput kapooth, blat, sput, brut, blahhhhhhhh. dit, blooth.
MMMM

. So without even taking off the tank I yanked the tube holus bolus, off the bike. The cause of the problem was the tip over valve had seized. In other words it wasn't letting enough air in to pressurise the tank and hence my Sheila was being starved of her Breakie

.
So for all you fellas and lassies out there who may come across this situation, it may just be the over flow valve or tube that's the culprit.
For me, I'm yet order a vented fuel cap and I would strongly advise others to do likely, just to ensure this doesn't happen to you.
Staffo