Out of all the wearable components on a motorcycle, I would wager a bet that the most overlooked system is the bike’s suspension.
What starts life as a set of taught and responsive forks slowly degrades into a mushy and unpredictable pair of pogo sticks. For those that find themselves at the track a few times a year, suspension maintenance becomes just as important as changing the engine oil.
However, if you’re anything like me and spend most of your miles on the street, then it’s no wonder why suspension maintenance goes by the wayside. If bumps are being absorbed and nothing is leaking, then everything must be fine!
Well, think again. More than likely, you are overdue for a suspension overhaul.
Let’s stop deferring this bit of important bike maintenance and get down to it. I’m going to show you how to completely refresh the forks on your motorcycle.
(Note: The procedure shown below highlights how Showa upside-down damper rod forks are disassembled and reassembled. Be sure to research the peculiarities of your specific forks when attempting an overhaul.)
Before starting, you will want to make sure you have all the special tools and replacement parts at the ready. This includes new fork seals, dust seals, and fork seal grease. You will also need to determine the correct volume and weight of fork oil that you will be replacing.
The critical tools you will need are a fork seal driver, a spring compressor, a vise, and an oil level gauge. All of the other tools used throughout the process are not specialized and can be easily sourced locally.
The first order of business is to get the front of the bike lifted off of the ground. The bike will need to be supported in such a way that puts no load on the front suspension. In this example, I am using a front end stand that supports the bike from the head tube of the bike’s frame. There are numerous “free” ways to accomplish lifting the bike, but do try to use your head and be safe about it.
If you ride a fully-faired bike like the Ducati in this example, you will need to remove most of the bodywork forward of the gas tank.
With the body work out of the way, the next step is to remove the front wheel. This is a great opportunity to check out those wheel bearings and front brake pads and replace them if necessary.
Removing the forks at this point is fairly straightforward. There are two clamping plates that secure the forks to the bike; these are known as triple trees. Loosen the clamp bolts for both fork legs and then slide the forks out the bottom. It may take a little wiggling to get them to budge but they will come out.
With the forks off of the bike and sat on the bench, take some time to admire their beautiful craftsmanship. Observe the precisely machined surfaces and brightly colored anodized finishes. Now, understand how easy it is to completely screw all of that up if you were to drop one. From here on, take your time and be patient.
Secure the fork tube in a vise that has been outfitted with “soft” vise jaws. These jaws, which are made from hard rubber, will prevent marring of the aluminum fork tube and allow for a secure grip. The first step in the disassembly is to remove the preload adjuster. This just screws off of the top, but it’s important to wrap the nut in electrical tape to protect the aluminum surface.
The next step is to remove the fork cap, which is the only piece preventing all of the fork oil from pouring out on the floor. Make sure the fork leg is vertical during this. Again, wrap the flats of the nut in electrical tape to prevent scratching the anodized surface of the cap.
When the cap is unscrewed, it is time to compress the fork spring. The spring isn’t very difficult to depress, but you will need the special fork spring compressor tool to hold everything in place while you remove the fork cap (red) from the damper rod (blue). Run a metal rod through the bottom of the fork leg (where the axle passes through), and then use two ratchet straps to compress the internal fork spring.
With the spring compressed, unscrew the fork cap from the damper rod. These may be a little hard to break loose from one another. I found that using an electric impact gun on the fork cap did the trick and no damage was encountered.
With the fork cap out of the way, relieve the tension on the fork spring and remove the spring compressor tool. Pull out all of the internals of the fork which will included some washers, the spring, and some metal collars. With the innards out of the way, it is time to turn the fork upside-down and drain out all of the old fork oil. It’s a good idea to let this drip for about 10 minutes to reduce the impending mess found in the next step.
Now it’s time to remove the fork seals and separate the inner and outer fork legs. The first order of business is to pry out the dust seal. This can be accomplished with a small screwdriver with the end wrapped in electrical tape (again, to prevent scratching the delicate surfaces).
With the dust seal out of the way, you can get to the retaining clip that holds in the fork seal. This clip is easily pulled out of its groove with a small screwdriver. The final step is to remove the fork seal. The method to dislodge the fork seal is quite primitive—simply yank the inner and outer fork tubes in opposing directions a couple of times. Make sure you have a firm hold on each tube to ensure that neither goes flying across the garage when the seal eventually loses its firm grasp.
At this point, the two tubes are fully separated from one another. Slide the bushes, washers, seals, and clips off of the inner tube and lay them out in order on the bench. Laying these pieces out in the order in which they were removed will help immensely upon reassembly.
Thoroughly clean all metal pieces with a rag and brake parts cleaner. Doing this will remove all residual fork oil and other foreign debris that has been collected during the disassembly process.
The reassembly is straight forward, but it is critical to put all items back in the exact same order in which you removed them. Do not screw up the order of seals, as once you install them, you will be hard pressed to remove them without damaging them.
Smear some fork seal grease around the lips of the dust seal and fork seal. Before slipping the seals onto the fork tube, place plastic wrapping around the fork leg. I used a twist tie bag for this. The plastic wrapping minimizes the change of the seals getting hung up on the sharp edges near the top of the fork tube.
Carefully slip the dust seal and fork seal onto the fork tube. These seals fit snugly on the tube and will take a little maneuvering to get them seated properly. Be gentle with the seals and eventually they will go on.
Next, slide the washer and bushes back onto the fork tube. Be sure to coat the bushes in new fork oil to ensure lubrication is there from the start.
Now, slide the inner fork tube into the outer fork tube. Once this is done, it is time to seat the fork seal. This procedure requires the use of a fork seal driver tool. I found that suspending the inner fork tube with a bungee cord tied to the bench vise eliminated the headache of it falling down while attempting to drive home the fork seal.
The seal driver tool I used was a two-piece design. The bottom piece, made of nylon, which contacts the seal, is shaped in a way to press the seal into the recess of the fork tube. The upper piece, made of a heavy metal, acts as a slide hammer to smack the seal into position. With a few swift whacks, the seal was properly seated in the fork tube.
Snap the seal retainer clip back into its recessed channel of the outer fork tube, then slide the dust seal down. The dust seal takes a bit of force to press into the fork tube. I found that seal driver tool worked well to evenly press the dust seal into place.
Now that the fork seals are installed, it is time to fill the fork up with new fork oil. Place the fork in the vise and secure the bottom of the fork in the fully-compressed position with a bungee cord. Then, fill up the fork with new oil. I filled up the fork with about half a liter of oil, which I knew was more than the required amount for these particular forks.
It’s alright because we will subtract the excess oil later on. Once the oil is in the fork, it is time to bleed the damper rod. This is accomplished by pumping the rod up and down about 10 times. You will notice that the rod’s resistance to movement will increase greatly as the air is bled from the system.
More than likely, you added too much oil to forks in the previous step. It’s all good because the fork oil gauge tool will set the oil level to the precise level that the factory calls for. To do this, first verify that the fork leg is still fully compressed.
Then, measure the distance from the end of the oil level probe to the desired distance, then set the stopper (the little round aluminum piece) to the correct distance. Slide the probe into the fork tube and draw out the excess oil with syringe.
That’s all it takes! Now you can drop all of the inner components, such as the fork spring and collars, back into the fork tube.
It’s now time to compress the fork spring and reattach the fork cap to the damper rod. Using the same compressing method we used earlier when we removed the fork cap, reinstalling the fork cap will go off without a hitch. With the fork cap screwed into the fork tube, the preload adjuster nut can be reinstalled. With that, the fork overhaul is complete! Rinse and repeat for the other fork leg.
Installing the forks into the bike is simply the reverse of removal. Make sure that the fork legs sit evenly with each other in the triple trees, then clamp them down. With both fork legs equipped with new seals and filled with new oil, we can rest assured that the front end of the bike will now be plush and predictable.
Special Tools Cost: $123.23
Parts Cost: $63.05
Total Cost: $186.28
Labor Hours: 6
Rebuilding the front suspension of your bike can prove to have a steep learning curve, but don’t let that dissuade you. For less than the price of having a professional do the job, you can acquire the tools and parts to do the overhaul for a lifetime of bikes. After performing this job you will have a better understanding of how the suspension on your bike works. You will have the satisfaction that front end is back to like-new condition.
Ultimately, you will have a new found confidence when you approach that next apex—on track or the street. That alone will make all the difference.
Peter Monshizadeh is the Practical Enthusiast.