The developer of this file made the cylindrical part 6 mm too tall to fit the newer model generators oil fill door. The manufacturer may have changed the dimension of the part.
I tried to just extrude down the top by 6 mm but cannot select all the little slices properly when I import the part into Sketchup. I need the top part of the cylinder to still contain the solid part as thats what the thumbscrew screws up against. I am pulling my hair out trying to find an easy way to do this.
Here is a picture of the one that I printed on the right that is 6 mm too tall and the one on the left which is the original part from the generator. ! The one on the left is 16.6 mm and the one that I printed is 22.6 mm tall. PredatorVentedCover|690x388
Run ThomThom’s CleanUp3 to get rid of the unneeded geometry first. Or just select all of the geometry and use the Move tool instead of trying to do it with Push/Pull.
You can select the top in a left->right window that includes the inner ring and then lower the selection by 6 mm. I just did but that makes it 16.5 mm.
Look at your model in from the side (maybe even in ‘Parallel Projection’ mode to make selecting easier.
I took DaveR 's suggestion above and used Thom Toms Cleanup on the imported .stl file. This removed all of the needless geometery and allowed me to just extrude the cylinder and inner cylinder down by 6mm. Worked perfect! Thanks @DaveR ! Thanks for all the quick help!