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Some questions concerning fork seal replacement


PeterSonic

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On my '18 1200RT, I just did a RH fork seal replacement.  However, there are a few things I need to know to put everything back together.

1.  How much oil?  I've seen 500 to 545ml

2.  torque settings for the axle itself and also the bolt on top that goes into handle bar

3.  When do I put the bleed screw back in?  After the forks are aligned or after the whole front end is assembled with wheel off ground or on ground?

4.  Do I need to remove the LH bleed screw also to "equalize" that both forks will have same pressure?

 

Thanks for your help!

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This is a direct copy and paste from another post I have up here on the forum.

https://www.bmwsporttouring.com/topic/98364-fork-oilseals/?do=findComment&comment=1063319

 

You can do a search for this kind of thing in the upper RH part of the Home page and see what has been answered before.

 

 

 

I had a weeping RH fork seal on my 2016RT 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.

image.png.30192f89b8bc1f02e23f26ab1d153c2e.png

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.

image.png.33c2ad7c1284041aff1fde621c0b850a.png     image.png.f6c6e8d2943db7a383d43c4ce8586ed7.png

   

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.

image.png.36d24f6e5bb515737e8f869c42d19d72.png

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 next 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.

image.png.242167c545224ecce56ca9d0c2b2d9bd.png  image.png.de7303d68ac972f06345157938f3356e.png

   

 

image.png.52d8a4ad281bf2d2305db5ca0f307c6c.png

  

 

Next I 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.

The oil in the lower slider leg is not going thru any orifices or shim stacks, so the weight of the oil is not very important…it's just there to lubricate the stanchions on the sliding guide elements in the leg…so 10W fork oil is fine…use 7.5W if that's all you have.

 

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.

image.png.e8694fca75ed39da8db76a670e8c389f.png.  image.png.c5d2378489f8dd816399495c106afdca.png

   

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.

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