If the bike sat for almost a year with ethanol gas in it, it probably needs a thorough carb and tank cleaning. High octane gas will do nothing to help the carb....it's a waste of money...UNLESS it is non-ethanol....if so, you can mix it with regular octane E10 50/50. That will give you about 88 octane, but more importantly only 5% ethanol.....much better. Since it seems to run OK after warm-up, try three ounces of SeaFoam per tank two or three times, that may clear it up.
Also drill the plug on the idle jet needle, remove it with a drywall screw, bottom out the needle gently and then out 2.5 turns.
Change the oil immediately! 250 miles is only partially broken in, so continue the break-in with regular dino oil and 500 mile changes to 1,500 miles before switching to all synthetic. DO NOT buy a new oil filter!!!! Just inspect and clean the OEM one for many thousands of miles....that way you will never risk destroying the engine with the wrong filter, as WAY too many of us have.