Warped prints on certain shapes

Circles and squares look great, but my printer is having serious issues printing gears. The teeth of the gear easily distort and tend to point upwards (toward the print head) while printing, and the end result is lopsided and wobbly, and a poor excuse for a gear! There are also some small blobs spread around the surface of the gear. Here are some pics of the print.

After perusing the troubleshooting guide on the wiki, I might try experimenting with a lower bed temperature, although I haven't had this problem with more regular shapes and my print problem looks different from the one in the guide.

Any suggestions as to what I should try to fix this?

From the top layer, it looks like you're not extruding enough filament and it may be that the print head is exerting a dragging force on the gear teeth as a result and pulling them up (similar thing happens when you try to print a small vertical hold for a bolt and it ends up being smaller than you designed). Try playing with the extrusion width over thickness settings.

Also, are you printing in PLA? If so, do you have an active cooling fan directed at the print? Cooling helps. You could try printing two gears side-by-side as this will give each time to cool properly as they print.

I am printing ABS, I have experimented with the extrusion amount offset in Slic3r, added a fan, am printing at a lower Z-resolution, and am using a different gear model that does not taper up at the bottom. The print looks a lot better; the problem of the gears lifting has disappeared, but there's still some inconsistency in the layers, and the hole is printing a little too small to fit on the motor without drilling out.

Here are some more recent pics.

The first image is a print-in-progress showing the kind of lifting I was getting before. The second image is my latest attempt (left) compared with the thing I am trying to copy (right). The accuracy just isn't there, especially in the details of the teeth. I'm not sure what to try next.

Try to reduce the bed temperature after the first layer, and and raise the hotend temperature, if you are not allready in the 240 degree range.

A fan is usually bad for ABS, it's better to print more parts at a time, and/or reduce speed.