This is not a difficult installation. I am not a mechanic but enjoy learning how to work on my own bikes. Recently I purchased on Ebay a backrest (HD #51631-09) and bracket (HD# 52587-09). This is the first time I have posted an installation on HD Forums so I apologize if make some sort of positng mistake.
Step 1: Remove rider left side bag. Remove seat strap from rider left side. One bolt holds strap on. Lay strap over seat to the right side. Remove Phillips screw head behind seat that attaches to your rear fender. This should release your seat by pulling seat back to release front tab.
Step 2: Install removeable tab to the wall of the bracket behind battery. There should be a small hole already there for it. I had to enlarge the hole with a drill for bolt to fit through. It is tight behind bracket so I took a needle nosed pliers and held the nut with it behind the bracket and gently screwed the bolt into it from above. Then I used an open end wrench to snug it but not tighten it. This way you can move it to the side when installing large bracket. This is shown in next picture.
Step 3: See picture. There are two bolt screwed in from under the rear fender that you will use. Loosen but not remove both nuts. I tied fish line to each in case either falls down into rear tire. Now remove nuts all the way. Try to not hit either of the bolts in fender now because only the nylon stops are holding them. Gently place your bracket (welded side with drilled holes towards front of bike to attach tab later) over the two bolts and intall nuts and tighten. I am 5'8" so I used the 2nd pr. of holes in the bracket counting from the right side of the bracket. (It was fine for me when I finished). I then cut the fishline off.
Step 4: Now move your tab that you had attached to the battery bracket wall towards the front of the bracket and align your holes. I had to do some bending with channel locks to align holes in order to intall bolt.
Step 5: Tighten all bolts. I used a little blue threadlock on each.
Step 6. Replace seat. With my hand I opened the hole for the backrest to fit through the seat to first of all see where I have to install backrest prongs. Install backrest to see if it is comfortable to you. Make sure you squeeze the spring loaded prongs enough to fit down into the bracket and that there are in the same corresponding holes on each side of bracket. If it is...leave it alone and attach seat strap and left bag.
Step 7: Go ride and enjoy your back support now!!

My only regrets for this post is I wish I had provided the size of wrenches needed and the pictures were larger for you. But I do hope it will help someone in some way. Good luck and ride safe!

 

If you buy a new bracket kit it comes with a clip and captive nut or threaded hole to slip over the battery bracket and you don't need to hold a nut on the back.
You can go here and get almost all of HD instructions on PDF.
http://www.harley-davidson.com/gma/g...3&default=none

 

If you buy a new bracket kit it comes with a clip and captive nut or threaded hole to slip over the battery bracket and you don't need to hold a nut on the back.
You can go here and get almost all of HD instructions on PDF.
http://www.harley-davidson.com/gma/g...3&default=none

 

Thanks X Iron Butt...as I stated in my post I purchased mine on Ebay and had no instructions. I wish I would have known. Thanks again for your addition.

 

Here is the link for the mounting kit in case you did not find it. The best thing about having these instructions is the parts list for all of the components and their availability. I save these in my HD folder for all of the parts I buy. After a part goes obsolete with HD the pdf files are hard to find.
http://www.harley-davidson.com/gma/g...8&default=none