Take the air box off and repeat the experiment. When it's sitting there on the stand revving like mad (when you would usually push the choke down), take a quick (and careful! watch the chain!) look down the back of the carb. If the throttle slide is all the way up even though you've returned the throttle grip back to zero (no throttle) then yeah, something in the carb is sticking.
Either way, it wouldn't be a bad idea to clean your carb and check for air leaks after you're done. And if you don't want to do that, check for air leaks before you go tightening everything down. You might not have air leaks in some places (or in any places) -- why risk stripping something if you aren't leaking there?