I unscrewed the two black bolts on the side of my mixer and two springs popped out. I put them back in and now my mixer will not work at all

They are the motor brushes, you do not need to fiddle about with them. Take them out again, look at them, one corner is missing from the carbon block. Look in the hole with a torch, right at the bottom there is a small blocker in one corner, line up your missing corner on the brush with the blocker and put it back together. Stop fiddling about and make a cake.

Hi, check the motor brushes. You'll see two black plugs with flathead screwdrivera small one, Unscrew to check, if only springs or very worn, you'll know It's a maintenance problem.

I believe the brushes and the spring are one piece, so the brush should come out with the spring. Either the brushes are so worn that you just aren't noticing the little bit that's left, or the block has come loose from the spring. You can tip the machine over so the brush hole is facing down and let gravity do the work. If there's any brush left inside, it should slide out. Otherwise just install the new brushes.

They are the brush springs. The brushes get caked up with burned flour. Remove the brush caps and pull the brushes out by their springs, being VERY careful to note the position of them since they only go back in one way. Measure the free length of the spring before pulling it out. It is critical that you write down the length sticking out with very slight pressure on it so that it is seated against the armature when you measure.

Clean the curved surface of the carbon brushes with a sharp knife being careful not to scratch the curved surface. If you have them installed wrong they will not go all the way in and will not contact the armature and it will not run. Measure the length, as done above, of the spring to make sure it is in correctly!! If it is not in correctly the spring will stick out 1/4 inch longer than it should.

Remove those plastic caps again and this time remove the brushes from the side of the mixing head. Inspect the curved surface of the brush and clean any carbonized flour from the surface - be careful not to damage the surface of the carbon brush.

When replacing the brushes make sure they go in the correct way - there is only one way, the brushes will not go in far enough if they are in the wrong orientation. Trial and error works, watching how far in the brushes go. once you have found the correct position, the brush will go in 1/4 inch further than the other three positions.

http://shared.whirlpoolcorp.com/assets/pdfs/literature/Repair%20Part%20List%20-%208212057.pdf

has a diagram of the locking mechanism item 9. The screw you removed was probably item 8. Look at the parts and you should be able to figure out how to get it back together.

I would first check that the motor brushes aren't worn out. They are held behind the black blastic caps on either side of the mixer head. These caps unscrew and the motor brushes are held in with a spring. Note the direction they go in, they are keyed and will only work when put in the right way. Use a torch to check. There is a picture of a new brush here: http://kitchenaidmixerspares.co.uk/Home/tabid/36/ProductID/88/Default.aspx

If this is not the problem the next stage would be to take the head apart to check the state of the gears and grease.

I would first check that the motor brushes aren't worn out. They are held behind the black blastic caps on either side of the mixer head. These caps unscrew and the motor brushes are held in with a spring. Note the direction they go in, they are keyed and will only work when put in the right way. Use a torch to check. There is a picture of a new brush here: http://kitchenaidmixerspares.co.uk/Home/tabid/36/ProductID/88/Default.aspx

Check the motor brushes. You'll see two black plugs with flathead screwdrivera small one, Unscrew to check, if only springs or very worn,youll,know.Its a maintenance problem.

Mine did the same thing. I found the ball bearing inside the switch had fallen off. Put it back on and it works like new!

Pull the mixer case apart. Push in on the seam in the front and back and it will pop open after you remove the 1 screw. Pull the switch apart. There is a spring inside the top part of the switch and a small (1/8") ball bearing should be on top of the spring. Chances are, it has fallen off. Find it and stick it back on the spring while holding the top part of the switch upside down. Put the mixer back together.