As many of you Tri-Z owners know the rear shock is prone to leaking past the seal head, especially after 30 years. Unfortunately, the shock’s design forced many owners to conclude it is not fully rebuildable, i.e., you can’t replace the seal head, and therefore you have to replace it with a shock off a Warrior or an expensive aftermarket shock. Well, I found a way to fully rebuild the Tri-Z shock for 40 bucks, i.e., the cost of a new head seal for a Banshee, Warrior, Raptor (they all take the same seal). I used the All Balls seal kit and it looks like a quality product. You'll only need tools most of us shade-tree mechanics have around the house: a drill, grinding wheel, file, fine sand paper, 8mm tap, and red Locktite. The process is as follows (I’ve attached pictures showing all the major steps).
1) Use the grinding wheel to grind down the button holding the shock valve on. I ground the diameter down from the sides (and not the top) so I could slip the valve off. Needless to say, you need to be careful with the grinder so as to not damage the valve.
2) Open up the rebound circuit (the pre-existing hole at the end of the shaft) with a drill so you can tap it with an 8mm tap (I used a 1.25 pitch thread). The needle valve that controls the rebound is located approximately 1 inch down the shaft. Be sure not to drill into it with the bit. You should have about ½ to ¾ inches of internal threads after this process.
3) File and sand the end of the shaft to where it is perfectly flat and a hair’s width shorter than the stack height of the valve. You want the bolt to bind the stack a bit when fully tightened.
4) Buy a hardened steel bolt (and small washer) that fully threads into the hole. You'll want it as long as possible for reasons of strength, but you also want the head to bottom out on the end of the shaft. This may take some cutting and filling to get it to the right length.
5) Drill a small hole (I used a 3/32 bit) down the center of the bolt. I also drilled small V-shaped bevels on either end to help with the flow. This is your new rebound circuit. Don’t make the hole too big or you will compromise the strength of the head. I have already ridden my Z with the new shock and the 3/32 hole allows for all the adjustability of the OEM shock, with the caveat that you can dial in even more damping (good for tighter or harder spring settings) because of the smaller hole.
6) The All Balls seal head comes with a rubber rebound damper installed on the bottom of the head, so you will not need to reinstall the OEM damper. I installed a washer the size of the damper on the shaft (between the valve head and the seal head) to prevent the damper from being damaged during rebound. With the bottom out bumper, seal head, and valve stack in place, thread the bolt (with a small washer) into the shaft and tightened. I used red Loctite to prevent it from coming loose.
Attachment 209354
7) Enjoy years of leak-free riding. Here's my Z.
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Originally Posted by Red Rider
