<p>I have a Monoprice Maker Select Plus (Wanhao Duplicator i3 clone) and I'm having issued with the top layer of my prints. The bottom surface and the sides always come out perfect but my top layer is left with gaps in it. I have tried adjusting the print temperature, flow rate, print speed and layer height all with no success. I use Cura for my slicing software. If anyone knows how to help it'd be much appreciated</p>
<p><a href="https://i.stack.imgur.com/MZFpf.jpg" rel="nofollow noreferrer" title="Closeup of failed print"><img src="https://i.stack.imgur.com/MZFpf.jpg" alt="Closeup of failed print" title="Closeup of failed print" /></a></p>
<p><a href="https://i.stack.imgur.com/45rzs.jpg" rel="nofollow noreferrer" title="Failed print"><img src="https://i.stack.imgur.com/45rzs.jpg" alt="Failed print" title="Failed print" /></a></p>

This is probably caused by too few top layers in combination with a too low infill percentage. Increase skin layers and increase infill percentage.
If you have multiple layers already (at least about 4 for 0.2 mm layer height, for smaller layer heights even more), you might be printing at a too high temperature and or too few part cooling percentage and a too low infill percentage.