"Ok, most times when something
"Ok, most times when something like this happens after the "last time out running fine" it is fuel related.
But, to be sure it wouldn't hurt to check the spark at all cylinders when you notice this issue. If you can get ahold of a timing light and rig it up to watch when you notice the power loss, that could rule out (or include) an ignition problem.
With the new E10 fuels (those containing up to 10% ethanol, alcohol or metanol) your carb(s), filters, gas lines can be fine one day and clogged or gummed the next. The alcohol really cleans your system out, but does so by loosening every bit of crud/varnish stuck to your fuel system and clogging something when it does.
So I would check the easy stuff first - fuel pick-up in the tank, hose connections (could be extra air getting in), fuel filter, water separator (if equipped).
If all those are ok, and your ignition looked to be good, the high speed carb jets may be gummed or partially clogged - requiring a good cleaning..."