string trimmer carb problem

I have a fairly new Ryobi string trimmer. When it's stone cold, it starts fairly well, and starts good at operating temperature if it doesn't sit around for more than about 1 minute.
When the trimmer sits for more than a minute or two "hot," it won't start for love nor money. The problem is that there is no gas in the line! Gas won't stay in the line. I choke it and pull to get gas to the carb, but by the time I unchoke and pull again to start it, the gas has all boiled back up into the tank. I use the primer bulb to fill the fuel line, and as soon as I stop pumping, the gas bubbles back up into the tank!
What is going on? What can I do about it? I suspect an air leak, but I can't find one. All the fuel lines look solid and intact.
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It sounds like vaporlock. See if a different Low octane gas helps, a thick carb to motor gasket might help.
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m Ransley wrote:

I knew there was a technical term for it, but I've got so many technical terms running through my head these days... Thanks.
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snipped-for-privacy@rochester.rr.com wrote:

Could be the fuel tank isn't venting properly- usually done in the cap.
Dave
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