A little heat from a hair dryer on the cylinder usually frees them up in a few minutes. Just install a prop and heat it up till it is just a bit too hot to hold for more than a second or two, a little pressure on the prop will usually free it up enough to get a couple drops of fuel into the cylinder. Then you are good to go. As someone else mentioned, make sure the reed is free before you put it all back together.

I think there are youtube videos concerning this issue, you might check it out.