This is how i restored the shine to my motorcycle forks on a 1985 honda shadow vt700 while replacing the fork seals. You don't have to replace the seals while doing this, but since you'll have the forks off anyways, it's a good idea. Take a look at the bushings too while you're at it.
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Step 1: Remove the Forks
The first step is to remove the forks. This process should be covered in a shop manual for your bike if you have one. If not, remove the brake calipers and the front wheel. Then loosen everything you can while the forks are still attached, it makes it much easier to disassemble them in the next steps, and keeps you from having to put them in a vice. Be sure to get the bolt on the bottom, but keep it finger tight to prevent the fork oil from draining yet. And loosen the cap on top with a crescent wrench, it's the part with an air valve. Then loosen the necessary bolts on the fork brace and steering stem to let the forks slide out.
Step 2: Disassemble the Forks
This process will also be covered in a shop manual. For this bike, I began by removing the oil drain bolt on the lower end of the fork, and draining the fork oil. It helps to depress the air valve on top so the oil drains faster. Then i removed the bolt on the bottom, and removed the cap on top containing the air valve. Be careful with this part, as the cap is under spring pressure. Once it's off, the spacer, washer, and spring fall right out. It's a pretty messy job, so wear some old clothes and have a work station set up. Next, a flathead screwdriver will get the dustcover off of the lower half of the fork, and it slides up over the fork tube. This gives you access to the seals, which are held in place by some form of clip. They were a pain to remove on this bike. Then by pulling up on the fork tube a few times, the seal should pop out and everything should come apart. The worn out bushing is shown in the picture. You can see the teflon coating has worn off and they need replaced. At this point, clean your parts and wash off the lower forks so we have a clean surface to start with.
Step 3: Removing the Old Finish
These forks were clear coated from the factory. So i used aircraft remover to strip the coating off without damaging the aluminum. It works in about 5 minutes, but be very careful with it if you take this route. It just gets coated on, and then hosed off. I hung the forks with some rope outside for that part.
Step 4: Start Sanding
Sand, sand, and sand some more. I started with 180 grit sandpaper, and then stepped up with wet or dry 400, 600,800, and 1000. Keep the forks pretty wet when doing it. You'll notice a huge difference immediately. Take your time and do a good job, as this is what determines how well your forks will look when you're done. Also, wear a mask and gloves when sanding aluminum, the chemicals released are pretty bad stuff, and you don't want it all over your skin, or in your lungs. Safety first.
Step 5: Time to Polish
Once you're satisfied with the sanding job, which took me a couple hours, wash everything off well. Then get some metal polish, such as the blue magic i have pictured. Make sure the polish is for aluminum too. Put some gloves and glasses on, and start rubbing on the polish with a soft rag until a black haze develops. It doesn't take long. Then buff it off with a buffing wheel, or a rag if you don't have a buffer, although the buffing makes a difference. When you're finished, wash it off again, and take a look at your hard work paying off. You're ready to reassemble now. Just reverse the process and be careful not to damage the seals. Use at least 600 grit sandpaper on the fork tubes to clean up any areas that aren't smooth to the touch.