Basic Dirtbike Maintenance 101 – Suspension Bearings

 How to inspect, maintain, and replace suspension bearings

Suspension Bearings
Ahh, my favorite maintenance item - rear suspension bearings! I once bought a KX-85 for one of my sons, and when I took the linkage apart to inspect the bearings for the first time, every one of them were dry and shot.  I literally had to replace every bearing on that Kawi.  I will cover “costly mistakes when buying a used bike” in a later post. The fact is that these bearings get a lot of abuse, are subject to the elements and power washing, and all together they are expensive to replace.  Keep them clean and lubed and your bike will perform better, and you will have more money to spend on that aftermarket pipe you want. So to keep things in good working order at the back of the bike, I inspect and grease the suspension bearings about four times a season. This article will show you how to inspect, clean, and replace the bearings if necessary.

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What you will need:

• Wrenches and sockets
• Long 3/8" extension
• Torque Wrench
• Waterproof grease
• Nitrile gloves

Inspection & Cleaning

• Get your bike up on the stand, remove the rear wheel, slide off the brake caliper, and loosen all of the linkage bolts.  This includes the swingarm bolt, the shock bolts, and the bolts that tie the linkage to the frame.  They are tight, so I use a beaker bar to loosen them, or you can also get a piece of ¾” metal conduit that is about 18 inches long, and use it to extend your ratchet.
• Now remove the bolts to the linkage, noting which ones go where (I will often use the exploded parts diagram from one of the motorcycle supply web sites, just print out the diagram and have it on your bench).
• Take each one of the linkage parts and set them on your work surface.
• Now remove the rear shock, and set it aside.
• If your brake line does not allow you to slide the line out of the guides, then remove the guides.
• Now remove the swingarm bolt.  I will take a long 3/8” extention, and use it to tap the bolt out through the frame and engine. Hold the swingarm while you do this. Once the bolt is out, set the swingarm on the bench.

Now take your suspension parts – one at a time – and do the following:

• Place the clean rag under the part, gently pry off the dust seal of the bearing, and slide the inner race out of the bearing.
• If the bearings all stay in place, and there is no dirt or grime on the rollers, and maybe even some grease still in here, your in luck.  Wipe off the inner race, smear some fresh waterproof grease on it, take your pinky and smear some fresh grease inside on the rollers, and slide that race back in. 
• clean any dirt off of the area around where the dust seal goes, clean the dust seals, smear some grease where the dust seals go, press them back on, and your ready for re-assembly.  

Of course, this is rarely the case. So read on.

• Take a small flathead screwdriver, and carefully pop out the bearing rollers. Once the first one comes out, the rest will follow pretty easy.  Be very careful not to loose any of the rollers. Keep the rollers from the different bearings separate, as some of them can be different sizes and length.
• Drop all the rollers and the dust seals into a bowl with some mineral spirits, and set them aside.
• Take the suspension parts into the kitchen sink, take some Dawn, hot water, and some brushes and get that thing sparkly clean.  Dry it off, blow it with some air, and bring it back to the work bench.  (Tell your wife you’re really sorry for getting the sink dirty, then tell her you are saving hundreds of dollars by doing this yourself.)
• Now take that bowl of bearing parts, and clean them (I use an old toothbrush, scotch brite, and rags.)  
• Dry the bearing parts – now you are ready for re-assembly.
• Take some of your trusty waterproof grease, and fill the cavity in the bearing where the rollers go.
• Now take some small needle-nose pliers, grab the rollers one at a time, dip them into the grease, and pack them back into the cage. As the cage fills up, you’ll need to take your small flat screwdriver and snug the rollers up to each other.
• After you pop the last one in, smear more grease on the rollers with your pinky.
• Smear some grease on the inner race, slide it back in, smear some more grease where the dust seals go, press them back on, and set that part aside.

Basically you do this with each part of your rear suspension, including the shock and swingarm bearings.

Now your ready to put it all back together.

• Refer to your notes and/or the parts diagram I mentioned to make sure you put the linkage back together correctly. This is sort of important. 
• I will put all the parts back together with the bolts hand-tight, then check that everything looks right, and moves well.
• Now take your trusty torque wrench and torque all the bolts to the specs noted in your manual.

Replacement
Replacing linkage and swingarm bearings might seem difficult, but with the right tools and a little patience its not a big deal.  You can buy special tools for bearing removal and installation, but again it’s not necessary.  I was able to make my own bearing removal/installation tool for less then $5.

Bearing Removal Tool

• About 12 inches of 3/8 inch threaded rod
• 2 bolts
• 4 large 3/8” flat washers
• 2 smaller 3/8” flat washers
• ½ drive sockets in various sizes

Obviously you will need to have the bearings on hand before you start the job.  If you are a planner, then you will have already bought them online, verses paying top dollar at the local motorcycle shop.  I usually use Pivotworks bearings, and I get them at MotoSport.com, and their prices are competative and the shipping is free when you go over $100.

Click Here for Swingarm Bearings

Click Here for Linkage Bearings

Click Here for Shock Bearings

(you can plug in your ride when selecting the bearings to get the correct fit)

Back to the removal - the concept is that you press out the old bearings, and press in the new ones. Before you start, take the new bearings and pop them into the freezer for an hour or so, which will cause them to contract a bit and they'll go in easier.

We’ll start assuming that you have already dis-assembled the rear suspension.

• Take the threaded rod, put a bolt on one end, screw it on about one inch, then slide a small washer, then two large washers on the long end.
• Now take a large ½ socket that is large enough that they bearing can fit inside it.  Slide the socket onto the threaded rod, with the opening facing away from the bolt.
• Now slide the open end of the threaded rod through the bearing race, and out the other side.
• Now take a socket that is big enough to make contact with the bearing, but small enough to slide through the hole that the bearing is seated into. A deep-well socket works better. The opening of the socket should be facing away from the bearing.
• Now pop two large washers on top of the socket, then a small washer, and finally a bolt.
• Hand-tighten the contraption so that the small socket snugs up against the edge of the bearing you are about to remove.
• Put a wrench on both bolts, and start tightening (a ratchet wrench works great here).
• As you tighten, the smaller socket will push the bearing out, pushing it into the cavity of the larger socket.  If the smaller socket is not long enough to fully push out the bearing, you may need to add another socket on top of it to get it all the way out.
• If there are two bearings in the part, just push them both out at once.
• Once the bearing is out, clean out the race really good, using a little emery paper to remove any corrosion.

To get the new bearings in, just use the tool in reverse fashion, pushing the bearing in instead of out.

• Put a little grease on the inside race to help it go in smoother.
• NEVER NEVER NEVER beat a bearing in – you will ruin it.
• When you first start the bearing, make sure that it does not tilt to one side, but keep it straight as it is going in.
• If there are two bearings, you will want to install them from opposite sides, stopping when the bearing is flush.
• Swingarm bearings will often be sunken into the race a small amount to leave room for the dust seal.  There is usually a ledge on the inside of the race where the bearing will be flush to.  If there is no ledge, then you may need to check it by fitting the dust seal every few turns of the bolt, and stopping when the dust seal is flush.
• Once the bearings are in, then smear liberal amounts of waterproof grease into the rollers, and onto the inner race before you assemble them.

That's it, you are ready for re-assembly.