Shindaiwa T20 string trimmer runs better upside down?
It's always difficult to get this T20 to run, but once warmed up it will run ok for a while. But after five minutes or so it will act like it's starved for fuel and shut off...unless I turn it upside down. If I do that just right, upside down for 30 seconds or so, then I can go back to right side up and it will work for a while until the same proceedure repeats itself. Sometimes it will run for many minutes, but always ends up starting to shut off which I can usually cure by turning it upside down. Sometimes when it shuts off, it won't start for a while, unless I use starting fluid (such as SureStart ether).
I've done the usual things, replaced/rebuilt the carb kit, cleaned out the muffler and made sure the exhaust outlet isn't plugged, adjusted it a million times. Replaced the fuel filter, run it without a fuel filter, run it directly from a hose to a tank of gas.
Since it seems to run ok when I connect a hose directly to a tank of gas, I suspect a problem with the fuel tank/breather system. But I don't exactly know how this works and what is most critical (ie, could a minute crack in the plastic tank affect the running, does the fuel cap gasket have anything to do with breathing...).
Could someone suggest how I would troubleshoot for this kind of problem, and especially what I need to check in the fuel tank system.