The shock is very easy to build indeed but a couple of things need to be done to get it perfect.
The 12x comes with a titanium nitride coated shock shaft which gives a very smooth shock action. The shaft is too long to give the ideal overall shock length though. The shock length controls the pod droop and keeping the shaft at the supplied length of 30mm gives far too much droop. With the extra spacer giving a more angled shock as shown earlier, the ideal overall shock length is 67mm. To obtain this the shock shaft will need to be shortened by 4mm. This is easiest done by using the cutting disc on a Dremel or similar. I measure 4mm down from the end of the shaft (make sure you get the correct end!) and wrap masking tape around it to mark the cutting point. This also makes sure the shaft is not damaged during cutting. Hold the shaft in a vice and cut it off at hte end of the masking tape.
Make sure that after cutting you sand or grind a small bevel on the end to remove any sharp edges. This makes sure you don’t damage any O rings when pushing the shaft through them.
The shaft should end up at 26mm or just over as seen below.
You can see all the parts necessary to build the shock in the picture below.
The piston needs to be put on the shaft first. It is quite fiddly and the E clips need to be pushed on with needle nose pliers so be careful not to mark the shaft when doing it.
When putting the white O ring in the bottom of the shaft I coat it all in plenty of shock slime. This makes it less likely that the O ring will be damaged and gives a better seal on the shock.
The shock should be filled to the brim with the shock oil from the kit. This oil is perfect for the shock. Then move the shaft up and down a few times slowly to remove any air bubbles. It is not essential, but ideally use a shock pump to remove any remaining air or leave upright for 24 hours. I’ve used an old touring car wheel as a stand to do this as below, they are just right!
When putting the cap on the shock screw it on halfway first. Then push the shaft half way down and tighten up the cap slowly whilst holding the shaft against a table or setup board so it doesn’t move while tightening. This will give a small amount of rebound in each direction. You should now have a more or less built shock as below.
Put on the spring and cap as in the instructions making sure the cap is fully on the shock shaft when you tighten it.
Then adjust so there is a 6mm gap as a starting point as in the picture below.
Screw on the end ball cup until the total length of the shock is 67mm when fully extended. This will give you the correct amount of pod droop when it is attached to the car.
Now the front roll mast/shock mount needs to be screwed onto the chassis. I Just make sure the bottom is totally flat by giving it a light sand with 600 grade wet and dry, it shouldn’t need much.
I also use a 3mm tap to tap the holes part of the way in to make it a bit easier to tighten, but it is not strictly necessary. Here it is mounted on the car.
Finally, snap the shock on as seen below. The front will only go on one way so make sure you have it the correct way round.