top of model not closing up

[Sideburn]

Hi, do any of you have any ideas on why this model is not closing for me? I have run it 4 times with different filament diameter settings as well as different infill settings but no luck.

It is the squirrel model onthingiverse http://www.thingiverse.com/thing:11705
and the top of his head always endsup with a hole in it

[3dkarma]

I can see holes in the back lower down as well. Either you are under-extruding or your bridging is not the best. First step is to follow the calibration guide on the reprap wiki - especially section 3.9. This will help you with your bridging. If you're still experiencing problems after calibration, try increasing your infill further.