They can be a little stubborn sometimes You only need to move the sleeve a few millimeters from were you got it to with the plastic tie, then you will be able to get a screw driver or similar under the lip and prise it out carefully from the top. I would suggest getting something plastic (I found the handle end of a toothbrush works well). Take the back plate off and rotate the piston to TDC. You will now be able to see the bottom of the sleeve by looking up into the crankcase/sleeve area. Nudge the bottom edge of the sleeve up with the toothbrush. This should move it enough to expose the lip on the top of the sleeve so you can prise it out.