What causes a hesitation upon accelerating on my yamaha vstar 1100 custom. I changed the plugs, changed the oil. The only thing I didn't do is change the gas that is currently in the tank. The bike has been sitting for a while.

yes

In many case when you rejet your carburetors you are only changing the mains and the needles(to get rid of the acceleration bog) If they give you several size jets to try, be sure you are putting the right sizes in the right spots. Yamaha typically will run one carburetor leaner than the other. Depending on how the cycle is running , I have known people to match the jets in both carburetors. Check the color of your plugs to double check if you have set the cycle up correctly.

Oil drain plug is located near the bottom of the engine, left side toward the front. The oil filter element is located on the right side of the engine under the cover toward the front. Changing the oil filter usually requires removal of the front exhaust pipe. There is an aftermarket filter relocation kit that replaces the filter element with a spin on filter that mounts on the front of the bike.

Sounds like it may be drawing air around the intake somewhere. Let it idle and spray around carefully with wd-40 until it speeds up. This will reveal the leak.

is it carbed or injection buddy

i think the oil filter is at the front behind a round finned cover, if you find the drain plug it should be right above it, it shoud tell you how much oil it takes right next to the filler