The fork seals on my nearly 20 year old, 2002 Kawasaki KL-250 Super Sherpa began weeping fluid about 1,300 miles following it's purchase in January 2021; total miles are at 7,000. I suspect that the leak is the result from a combination of age and the additional compression strapping it on my Black Widow receiver carrier.
It's been a long time since I used a hitch carrier and seem to have forgotten that the rear should be the end with the strong torque.
Anyway, I came home following completion of the rough and rocky Smokey Mountain 500 and the equally rough and rocky Hooch Dual Sport Rally in GA, TN and NC last month with a long list of "things" that I wanted to do with the Sherpa; mods, some repair, some maintenance. The fork seals were already on the list.
I purchased the All Balls replacement seals and wipers from RMATV for under $25. The OEM replacement parts were over $60 and All Balls is a well respected aftermarket brand name. Given that I consider the Super Sherpa is "budget" equipment, I went with the low cost option.
Although I previously owned a 2009 model year Super Sherpa, I had no experience replacing it's fork seals from either model year. However, I do own a Service Manual that covers the process, which I followed subject to the following.
The Service Manual indicates needs for special tools. One to hold the inner cylinder in place for extraction of the lower retaining bolt and one for pressing the fork seal into place. I do not have those special tools, nor did I need them.
Lower Retaining Bolt
In general, the lower retaining bolt connects to the fork cylinder that is inside the inner fork tube and holds the inner fork tube securely inside the fork bucket (see diagram from Service Manual below). I was able to remove the lower retaining bolt with an 8mm allen bit adapted on my air impact driver at a low-torque setting while exerting outward pressure on the inner fork tube with one hand.
Once the retaining bolt was removed using the 8mm allen bit, there was a cir-clip that holds the fork seal and fork wiper in place that required removal with a flat screw driver. At that point, the inner fork tube (with the Fork Cylinder inside) could be pulled out of the Fork Bucket; a couple hard pulls are in order and the seal and wiper will come out along with the inner fork tube as shown in the photo below. The old seals and wipers were slid off the inner fork tube and the new seals and wipers were slid on, awaiting re-installation of the inner fork tube in the bucket and their proper setting.
Fork Seal Press
The inner fork tube with the new seal and wiper must be (1) reassembled with the bucket and (2) the fork seal and wiper must be pressed into the groove in the bucket head. Once in place, the aforementioned cir-clip can be reinstalled.
(1) The retaining bolt should not be replaced with the air impact hammer. Rather, it is extremely important to reinstall the retaining bolt at the proper torque setting, which is 20 ft/lb. Over torquing the bolt could result in problems including the inability to remove the retaining bolt next time the seals need replacement or other servicing of the fork is necessary. Use a torque wrench. I found that the cylinder didn't spin when torquing in the retainer bolt.
(2) The service manual calls out use of a special too to press the seal in place. I did not have such tool.
The seal and wipers are soft rubber and can be ripped or otherwise damaged. The special tool is designed to avoid damage as it exerts a flat consistent pressure around the seal and then the wiper. Without the tool, the seal and wiper can be carefully pressed into place with other flat surfaced tools ... a screw driver or tool with sharp surfaces are not tools to be used. It's simply selecting the right tool and then exercising care and patience that will get the seal seated.
Once the seal and wipers are seated, the cir-clip was pressed back into place in the rim of the fork bucket.
As a general observation, I would like to add that I have been changing fork seals for decades and the design of the Super Sherpa makes seal replacement the easiest coming out and the easiest going in, certainly that I've experienced.
Fork Oil
I suppose fork oil could be saved and reused if it remains in good condition. However, it's usually more appropriate to change the fork oil when the fork is disassembled. In my case, the fork oil looked really bad after it's replacement a mere 1,300 mile ago when I purchased the bike. It had actually acquired that gray that motor oil gets when it's been used too much. I suspect that the prior fresh oil change had a cleaning affect.
The specified fork oil for the Super Sherpa is a Kayaba 10w (a fork-specific OE product) or SAE 10w-20. I used SAE 10w-20 for the change upon purchase in January. With the experience of having just completed three dual sport rallies, I decided to move to a slightly thicker, "dedicated" fork oil; specifically Maxima 20.
The thicker oil should increase the otherwise very minimal dampening affect of the Sherpa's forks, but I'll have to get some time on the trails to see if that's the right direction .... or far enough.
Fork Oil Volume:
The fork oil volume differs between regular changes and full disassembly.
- Regular fork oil changes, specified for every two years, 10.14 ounces/300 ml.
- Full disassembly, as was required for the seal replacements, 11.93 ounces/353 ml.
Fork Oil Level:
Generally, fork oil level check is a periodic maintenance item with a specified interval of 7,500 miles. While the service manual calls out a fork oil level check when the fork oil is changed, I don't necessarily see the need.
When having disassembled the fork, such as the seal change, all oil is removed. As noted above, the manufacturer specifies a volume of oil (11.93 ounces or 353 ml) to refill the fork. Since 353 ml is the specified volume, I would expect that volume of oil to produce the specified level, which for the North American Sherpa is 147mm +/- 2mm. In other words, during disassembly, the specifications for fork oil volume and fork oil level are, in fact, measurements of the same thing.
Fork oil level check, in my view, is more akin to checking your motor oil; sometimes we may need to add some, most of the time we don't.
Irrespective, following is an excerpt from the Service Manual on the Fork Oil Level Check. Note that a special tool is suggested. Similar to the special tools suggested for fork disassembly and seal/wiper installation, there are work-arounds for the special oil level test tool, as well.
The Special Tool for fork oil level test is actually a common and widely available tool.
Cycle Gear has such a tool for $22. The OEM tool is $80. However, the Special Tool is the quintessential definition of a
Rube Goldberg.
A family member once gave me one as a gift; never used it.
Essentially, the design of these tools is actually a syringe that will "extract fork" oil down to a specified measurement from the tube's rim; about 5.75 inches for the fully compressed fork for the Sherpa. It's just a check though! All we need is a simple measurement for the level check, a dipstick can be made for use out of any clean straight object that fits in the tube's inner diameter of 1.4" (36mm) and is longer than the specified level measure of 5.75 inches.
Just like the motor oil check, add fork oil as needed. Removal of oil during a check, which the special tool is designed for, is rare. Why?
Well, if the proper amounts of fork oil have been used for routine changes and disassemblies, where did the excess oil above specified levels/volumes come from? An overfill, both intentional and unintentional, is the only answer. And an intentional overfill is the basis upon which the special fork oil level tool works; in short, overfill the tube and extract the oil down to the proper level using the syringe.
If I may make a suggestion, just use correct amount of oil during changes, disassemblies and checks, and you won't need the $20-$80 tool.
