RT Fork Seals

Riding home yesterday, I looked down and noticed oil sitting atop the right fork seal. When I got home, I checked more closely and both fork seals are clearly leaking. I did hit a pot hole earlier in the day, but at the time I hadn't thought it was a particularly bad one.

Being a dirt biker, I tried cleaning the seals with a piece of heavy plastic film like you do to fix dirt bike seals, but after another ride they both seem to still be leaking.

My mechanic expressed surprise when I told him both were leaking - he said that was uncommon in his experience.

Anyone else out there experience fork seal leaks? And both at the same time?

I had this happen on my Harley many years ago. Replaced the seals and they did it again. While expressing my frustration one day someone asked me if I'd been using Armor-All to make the dust covers shine. Turned out that the Armor-All was the problem, it lubricates the seal too well causing leakage, which once it starts will not go away. Next set of seals I never used that stuff again, and never had another problem in the next 80,000 miles of riding. I don't know if this will help, but that's what happened in that instance.

I had a weeping RH fork seal from the middle of last summer and changed it out this winter. (67k to date)

The OEM part number is 31428532723 and is a set of parts for 2 fork tubes.


The service manual is nice and clear as to the process and it only took about 2hrs from start to finish with the bike up on my lift.
A tiny quantity of oil can look like a pretty large leak, it's deceiving how much dirt just a small amount can attract.


I tried cleaning up the original seal to find a cut or some crud on the lips of the seal, but didn't see anything unusual.
I used a universal seal puller to carefully remove the old seal. I'd recommend placing some kind of pad or protection against the edge of the fork to prevent leaving any marks or nicks in the metal.
The third picture shows the black coated surface that takes all the force on the top end of the fork tube before replacing the seals. There is a similar thrust surface in the lower end of the fork as well, but I didn't replace anything other than the top seal and wiper.




Next poured out the fork oil into a graduated cup and it was about 500ml. The manual calls for 545ml as well as measuring it during reassembly to be 90 +/-2mm from the top of the lower fork tube. The original fork oil was not contaminated/dirty, so I topped up the volume to 545ml in my pitcher and poured it in the lower tube. With this new volume, it measured from the upper lip of the tube about 75mm, so I kept pouring it out until the measurement was at 90mm...which just about equaled the 45ml I added in the first place...so almost no measurable loss of fork oil. A couple of drops of oil can look like a mess over time.



I used the Motion Pro 08-0551 bearing driver to drive the lower seal squarely to the spacer ring in the lower fork. It only took about 4 light hits with a hammer to drive it home. The new OEM seal comes pre lubed and the wiper seal just presses into the top of the lower fork tube.



Sliding the upper shiny tube into the new seals is simple and needs no tools or special procedure with the vent screw still out. When the upper fork slider is up in the top fork bracket next to the handle bar, you install a new top nut holding the slider to a torque of 40Nm, then you replace the vent screw with a new O ring.

Since I only was working on the RH fork, the LH fork tube is the alignment reference with the Quick Release Axle shaft between the 2 for setting the position in the lower clamp.

It instructions were VERY specific about torquing the 2 main pinch bolts in alternating fashion 3 times each to 19Nm.

There was never any degraded performance with the annoying small oil leak on this fork tube, but I was tired of seeing some oil and not knowing if it was a drop or a more serious leak.

This was a couple of hours well spent, I'd had enough of wiping down the fork at the end of each day of riding to see if it was getting worse...because I knew it was not going to get better on it's own.

Thanks!

Boxflyer said:

I had a weeping RH fork seal from the middle of last summer and changed it out this winter. (67k to date)

The OEM part number is 31428532723 and is a set of parts for 2 fork tubes.

The service manual is nice and clear as to the process and it only took about 2hrs from start to finish with the bike up on my lift.
A tiny quantity of oil can look like a pretty large leak, it's deceiving how much dirt just a small amount can attract.

...
This was a couple of hours well spent, I'd had enough of wiping down the fork at the end of each day of riding to see if it was getting worse...because I knew it was not going to get better on it's own.

Click to expand...

Wow, thanks for the detailed explanation of how to do it! It seems a lot simpler doing this on a telelever system than doing it on a conventional fork. I was going to take it to the mechanic, but maybe I'll do it myself now.

What's the spec on the fork oil?

Nice write-up. thanks. When do we get the video?

Hi Bob,
Most places I see it described as 10w and in a very few places I see it as optional 7.5w normal fork oil.
I've just been using 10w and have no issues.

The fluid in my forks was perfectly clean and there was no contamination of that oil, so I just reused what was in there (500ml)...measured to spec of 90 +/-2mm from the top of the lower fork tube.

BUT...the real takeaway here is that it really doesn't matter much what weight is used because the fork internals don't have any shim packs or orifices where metering a fluid of a specific viscosity changes reaction to road inputs.
The fluid in the our telelever front end is just a lubricant for the sliding fork leg to move freely on the stanchion (fixed leg).

Hope this helps...and I'll try to make a YouTube video in the future.

Boxflyer said:

BUT...the real takeaway here is that it really doesn't matter much what weight is used because the fork internals don't have any shim packs or orifices where metering a fluid of a specific viscosity changes reaction to road inputs.
The fluid in the our telelever front end is just a lubricant for the sliding fork leg to move freely on the stanchion (fixed leg).

Click to expand...

More excellent info. Thanks, Boxflyer!