KLR600 Fork Seals "Short-Cut"

Shortly after I purchased the 1985 Kawasaki KLR600B1 in April, I did an extensive maintenance on it that included refreshing the fork oil. The oil was pretty nasty, but at that time the seals were holding. In short though, the seals started to show leakage, most likely due to the higher (proper) level of fluid in the fork.

So on to the "normally dreaded" fork seal replacement....

If at all possible, I try to stick with OEM parts for maintenance. Sometimes the price tags are just too high compared to aftermarket options, but in the case of seals I was able to get a set from RMATV for $22. I did not get the wipers, only the seals.

Similar to my recent swingarm guard experience, I happened to be working in the general area so the amount disassembly wasn't too bad. Specifically, I will be replacing the front brake disc and doing some work on the caliper. So the wheel is off and the forks are easily accessible with four allen bolts per side.

The Short-Cut-Approach

In advance, I had reviewed online videos of early model KLR fork seal changes and found an interesting, new-to-me approach that I intended to apply.

Essentially, the "Short-Cut-Approach," as it's called, is to simply use air pressure in the fully assembled fork tube/bucket to blow the seals out. Early model KLRs like my 1985 have Schrader air pressure valves to support this approach. I've been changing fork seals for decades and the short cut saves a lot of time and effort in this maintenance procedure for forks with valves.

So here's how it went...not so good at first:

The first thing I had to do was drain all that good oil that I'd filled the forks with a couple weeks ago. It was reusable, but I needed to buy some more because I lost quite a little in the leakage. Other than remove the fork and drain the oil, I did nothing to the fork except wrap a rag around the fork to "catch" the seals that blow off.

In hindsight the wrap wasn't necessary, but that's what all the guys in the videos did so I followed suit.

I pumped up my portable air tank with 100 PSI for the initial "unsuccessful" attempts at applying the short -cut-approach. I was quite disappointed as guys on the YouTube vids were popping the seals out with around 40 PSI. My seals weren't budging for me even at 100. Maybe like the oil, they hadn't been changed in 35 years either.

After several unsuccessful attempts, I rev'ed up my 175 PSI air compressor and put some heat on the bucket around the seal. With those additional steps, the seals popped out with a bang equivalent to a 22 long rifle. Wow!

Dang! I've been changing fork seals literally for decades and this was by far the best experience I've ever had.

So, to continue with the job...

For purpose of installing the new seals, I found a piece of solid pvc pipe in my scrap pile that fit over the tube and inside the top of the bucket. I cut it down to extend past the top of the fork tube eight or so inches and used it to press the seal into place.

A good lube is in order for installing fork seals but it must be a dry lube. You don't want slippery oils and greases to linger in and around the seals. There are all kinds of options out there. WD40, which most of us have readily on hand, is a solvent rather than an oil, but evaporates fairly quickly and acts as a good lubricant for this purpose. However, I use this stuff because it's a non petroleum based lubricant that won't cause rubber deterioration like the WD40 does (although over such a long time, the seal will wear out before the WD40 does any harm to it).

Fork Oil....

Spec fork oil vicosity for the KLR per the service manual is SAE10. Personally, I've always felt that I get better suspension performance in forks using SAE20. However, back during the first fork maintenance the closest I could find was SAE15 at Sky Powersports. Close enough.

Fork oil specs usually come in three forms. The first is the viscosity, as discussed above. The second is the quantity and the third is the measurement from the top of the fork. Once the weight is selected, the third spec is more important than the second spec.

In the case of the KLR600B1, the quantity was 362 milliliters. The measurement from the top of the tube is 192 millimeters.

Note that the KLR600B1 specs changed from the KLR600A1 (1984) specs. The B1 specs for all post 1984 models can be found in the Service Manual Supplement.

For purposes of the measurement, the springs and other guts of the fork tube must be removed, the tube must be fully depressed and measured at the angle of the triple tree. For this purpose you may as well just put the tube in the tree, but make sure it's depressed.

In my case here, both forks required slightly more than the 362 milliliters to achieve the proper level in the forks (190 millimeters), but again, the measurement is the more important of the two specs....quantity and measurement.

So, that's was it. Done. What a pleasant maintenance experience changing the fork seals was on the KLR!


Up next....

More Brakes! Research has indicated to me that the brakes on the KLR600 suck...and always have. Well, they sure sucked when I bought the bike. So far I was twice in the rear drum getting that mess successfully straightened out.

Now I need to work on the front brake. I already added new brake pads, but didn't get the results that I wanted. So I purchased a new rotor and have some tinkering planned on the caliper to help get a tighter grab on the rotor.

Dang, I actually may have the old pig ready for The Hooch in two weeks. 😊