Thanks for the info.. I decided to build a shock press and change the oil in my Stock HD 12" SG shocks. I pumped out the original oil and installed 10 wt. oil. Won't be able to test drive it til spring. The shock oil change takes about 45 minutes to an hour to do including removing and installing the shocks.
Revived this old thread because I have some information that may help a brother save a few bucks modifying his stock rear suspension and also simplify the process.
Like many I found the stock 12" rear air shocks on my 14SG to ride very choppy! For $71 I obtained a brand new set of 13" (actually measure 12.75") take offs from a 2015 Harley. After reading about every thread on every forum pertaining to HD shocks I decided to change the stock 5 wt oil to something a bit heavier. This is really not a hard job and can be done as follows:
You will need shock oil and after much research I found the qualities of Amsoil Shock Therapy to be better than the other offerings (no I'm not an Amsoil guy. First time I've ever used the stuff) I chose it because it is synthetic and has a high VI rating. $10.99 a quart at my local NAPA store. Had it on hand.
You will also need a new clear mustard/katchup bottle. $1.77 at my local restaurant supply store.
Remove the brass air fittings from the shocks and stand them vertically in a container to drain. I used a small waste basket with rags on the bottom to soak up the oil. Could also hang them over a bucket. They will drain overnight. Rock them back and forth to make sure all the old oil (about 13oz) has drained. NOW if your in a HURRY stick the squeeze bottle in the hole, flip the shock upside down and squeeze a bit of air from bottle into shock. Air from bottle displaces fluid in shock. Fluid drains into bottle. Requires several squeezes and your shock is empty.
To refill hold shock vertically, right side up, insert squeeze bottle upside down with 12 oz of new shock oil. Squeeze bottle a bit and oil from bottle will displace air in shock. After several squeezes bottle is empty, shock is full. Install air fittings and your set to go. After my shocks had drained it took me about ten minutes to fill them.
I installed a Shrader valve on each shock. Actually they are chrome 1/8" NPT tank valves from ACE hardware. $1.99 each. I ran these for awhile but went back to the factory plastic air tubing for ease of adjustability.
I mixed 6oz of 10wt oil and 6oz of 5wt oil to effectively end up with 12oz of 7.5 wt oil in each shock.
Hope this helps someone who is thinking about swapping shocks or changing to heavier oil or just changing oil on older shocks that have a few miles on them.
Blues
