A Step By Step Guide To Rebuilding A Dirt Bike Shock


In this post, I will show you how to rebuild the shock on your motorcycle. In rebuilding the shocks you need few parts to do the job right including a variety of shock oils and seal kits. General tools are required as well as a few specialty tools. We’re going to need a tusk seal bullet, race tech seal head setting tool, tusk shock preload adjusting, and in some cases, the tusk shock reservoir cap removal tool.

To start, I’m going to spray a little bit of oil on the threads of the top of shock, and then loosen the top locknut. It’s a lot easier to do on the bike. And I’m going to pull my exhaust, take the seat off and then the tank. Now we can go ahead and loosen the air boot on the back of the carburetor, loosen the lower subframe bolts and then we’re going to remove the upper subframe bolt altogether.

This is going to allow the subframe to drop back a little bit, give us better access to the shock. Now we can remove the lower bolt and nut from the shock. Once that’s out, the swing arm will drop and then we can remove the nut washer and bolt from the upper shock.

Hold on to the shock while you remove the bolt, so the shock doesn’t drop. Once that’s out, we should be able to remove the shock from the motorcycle. If you have them done it already, now is a good time to put on safety glasses. If you want to save yourself some more work later, measure the length of the shock spring. This will make setting your sag a lot easier when you’re done.

I like to begin this assembly by releasing the nitrogen out of the shock reservoir. Then I’m going to loosen the locknut on the shock and then the lower nut. I’m going to do this by putting it in a vise in twisting the spring, once it’s loose, I can push it the rest of the way back with my finger, move the rubber bumper down. The collar will drop and you’ll be able to remove the retaining ring that holds the spring on.

Here I’m rebuilding a Kayaba shock. The procedure for a show of shock is pretty much the same, but removing the spring is a little bit different. You’ve got to kind of knock the two retaining collars loose from each other to reveal a small circlet on a show of shock. Once you use a little screwdriver or pick to remove that little circlet, you can separate the two collars and then remove the spring from the shock. That’s pretty much the main difference between a Showa and Kayaba shock. Back to our Kayaba shock, at the bottom of the shock, we have a little seal cover.

We’re just going to use a little punch, there’s two holes in this cover, we’re just going to tap on those holes to remove the cover and this will reveal our dust seal and the seal head right below that. We want to make sure to clean this really good. I’m going to use some contact cleaner in a rag, and using my race tech seal setting tool, I’m going to push down. I may have to release more of the pressure out of the reservoir as I push that down, it’s going to build pressure.

So I’m pushing the seal head down to reveal the small circlet that holds the seal head in place. Using a small screwdriver or pick, I’m going to remove the circlet, and once again I want to clean this area really well. It’s going to make the removal of the seal head a lot easier if it’s clean. At this point I’m going to remove the valve stem, I could have done this earlier but I’m going to remove it now and I’m going to mark the location of that stem in relation to my shock body, makes it easier to set up when I’m done.

Now I can push the bladder into the body of the shock and this is going to reveal the circlet that holds the bladder in place. So once again, using a small screw driver and pick, I’m going to work that circlet out. Sometimes, these are a little tricky, they take a little bit of patience. Once that’s out, again I’m going to clean this. It’s going to make the removal of the bladder a lot easier if it’s clean. I’m even going to use a little bit of air on both of them to make sure I don’t have any dust.

With the rag over the seal area of the shock, I’m going to carefully move the shaft of the shock up and down and work the seal head out of the shock. Dump the oil on a pan and following the seal head is the piston and valve stack. Now I’m going to work on removing the bladder, wiggle this back and forth, and then with the bladder out, I’m going to make sure all the oil is out of the shock.

On many shocks, it may be difficult to get a hole of the bladder cap to pull it out. The Showa shock showing here has a bladder cap that sits into the reservoir of the shock. If you have a shock with a centered valve stem like this, the tusk reservoir cap removal tool threads onto the valve stem and allows you to pull the cap and bladder out easily. With the bladder out, go ahead and clean the body of the shock.

I’m going to spray it out and wipe it out with a clean rag, and then I’m going to wipe off the bladder as well. To remove the seal head, we have to remove the piston and valve stack. And to do this, I’m going to wrap a rag around the piston and the valve stack, and wrap a little bit of tape on it to hold it tight. The shock shaft has been pinned on the outer edges and on the center hole.

The goal is to grind the peened edge off the nut so it can be remove on many shocks, especially Showa, it’s important not to grind the peening around the center hole. This peening keeps the rebound seat in place. Once you have ground the edge on the shaft around the nut, remove the rag and then remove the nut. Once the nut has been removed, I like to get a screwdriver, set it in the end of the shaft and pull the piston, valve stack, all the washers off together.

In that way, I can’t get it mixed up, there are a lot of washers here. These are used to control your valving and you don’t want to get those out of place. Then we can go ahead and remove the seal body and the little cap on the end. And since we’ve ground the end of the shaft, it’s a good idea to take a small pile and just make sure those threads are clean.

Using compressed air, I’m going to clean the shock shaft and I’m going to do the same to the piston and valve stacks in preparation for assembly. On my right, I have an all balls brand shock seal kit. It’s the complete seal head assembly, so it makes changing the seal on your bike convenient. We also sell seals and dust seal separately, and these can be installed on your existing seal head. To do that, we’re to pop the rubber O-ring out of the back side.

And then there’s going to be a washer and then the actual oil seal. Carefully pry that out with a screwdriver, pay attention to how it was sitting in the seal body, there’s another washer underneath, we’re going to clean that real well. And then using a screwdriver, we’re going to pry the dust seal off the top. Now we can install the new dust seal, we’re going to put some grease on it and then press it on to the seal body since this has a steel frame, it’s pretty tight so we’re going to use a socket to tap it on.

Once that’s on, we’re going to reassemble the oil seal, put the washer in, oiled up the seal put it in flat side down and then the other washer and then the rubber O-ring that sits right on top and holds everything together. So now we’re ready to start assembling the shock. You’ll notice on the shaft, this edge is very sharp. That’s where the seal bullet come in handy, slides over the end and kinda removes that sharp edge.

This will prevent you from cutting the new seal. Go ahead and slide the seal cap on and then the seal head assembly. Carefully slide it over the bullet and on to the shaft. With the seal head in place, we can remove the seal bullet and install the piston and valve stack. So putting the screwdriver back on the end of the shaft, I’m just going to carefully work all the little washers into place since I’ve kind of moved them around, it’s tricky lining up the line center hole on the shaft.

But keeping the screwdriver on everything keeps everything in order, so you can’t mess anything up. Once it’s in place, we’re going to install a new nut with high strength thread locker, go ahead and thread that onto the shaft. And then we’re going to torque the nut down to about 35 foot-pounds. Once that’s on, wipe off any excess thread locker and just to be safe, I’m going to put a couple punch marks between the nut and the shaft to work as another locker to make sure that nut doesn’t come off.

At this point, I want to loosen the compression adjuster all the way out, this makes oil flowing between the reservoir and shock body a little bit easier. So I’m going to pour a little bit of oil in, and I’m making sure it’s running through to the reservoir. If not, I’m going to tap it a little bit just to push the oil through and make sure we don’t get air caught in between. Then I’m going to fill the reservoir about halfway and install the bladder. And you want to make sure you have enough oil in that it’s pouring out like this, that way you know you have enough, you’re not getting air stuck inside.

I have a pan underneath to catch all the excess oil, and I’m just going to push the bladder and bladder cap down into the reservoir just far enough to reveal the little groove from my c-clip. And I’m going to put the c-clip in place. And notice I lined up the valve stem with the little mark on the reservoir there. I’m going to install the valve stem. Using the tusk suspension pump, fill the bladder to 40 to 50 psi.

This will allow me to safely see the bladder cap seat, as well as allowing the bladder to keep the correct volume in the reservoir while installing the shaft and seal head. A bicycle pump can be used as well but this tusk pump has a convenient pressure gauge built in. Do not use high pressure compressed air. Now we’re ready to install the shock shaft and seal head, we’re going to fill the rest of the shock body with oil close to the top and then we’re slowly going to work the piston and valving into the shock.

Once it’s in, we’re going to pump the shock up and down, you’re going to see a lot of bubbles come up might start foaming, let that settle a little bit ’til all the bubbles are gone. Once the bubbles are gone, we’re ready to push the seal head into the body of the shock. So I’m going to top off the shock with oil and then we’re going to push the seal head down into the body.

You’re going to notice you can only push so far and then the pressure won’t allow you to go in anymore so we’re going to have to remove the valve stem again using the race tech tool, we’re going to push the seal head into the body. We want to make sure we push this in far enough to expose the circlet groove again.

Once that’s exposed, we can install the clip, install the valve stem and then pump a little bit of air into the shock just enough to see that seal head seat. Once the seal head is seated, go ahead and put the cover back on, might have to carefully tap that own with the mallet. Once that’s in place, we’ll make sure the shock is clean, get all the oil off of it and then we can put the spring back on. Slide the spring over, and then their different collars. You’ll have to move the rubber bumper out of the way again, hold the spring up in place and then tighten the lower nut to the spring.

Continue to tighten the spring until you reach the spring length you started with before this assembly. The final step is to release any air pressure in the shock and then fill it with nitrogen. Only qualified and certified technicians should charge the nitrogen. Most shops can do this for a small fee. Install the shock on the bike and you’re ready to ride.

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