Some questions concerning fork seal replacement

[PeterSonic]

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!

[Boxflyer]

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.

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 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.

  

   

 

  

 

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.

.  

   

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.

[Audi403]

On 6/22/2022 at 10:00 PM, Boxflyer said:

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.

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 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.

  

   

 

  

 

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.

.  

   

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.

Hey Boxflyer,

 

Thank you for this post. I'm about to do this job on my R1250RT. I have the fork seal kit and I'm just about to purchase the correct tools for pulling the seal as well as driving the new seal in. I have a service manual for an R1200RT, as well as an R1250GS. Unfortunately, I haven’t been able to find the service manual for an R1250RT. I've been using the R1250GS manual for the engine work on my bike, and the R1200RT manual for pretty much everything else.

 

I did notice an interesting difference between the R1200RT and R1250GS manual in reference to disassembling and assembling the fork legs to change the seals. In the R1200RT manual, they do it a little differently than you. After the old seal is removed and the oil is filled to the correct level, they install the fixed fork tube into the slider tube before installing the new fork seal ("shaft sealing ring", as they refer to it). They then use a tool that slides over the fixed fork tube to tap the seal into place. What caught my attention was this note:

"If the fixed fork tube is pulled out of the slider tube past the limit of it's usual travel, the sharp-edged vent bore in the fixed fork tube can damage the shaft sealing ring in the slider tube. Do not pull the fixed fork tube out of the slider tube past the as-installed position."

 

My concern with this note is, if I install the new seal as you've shown before inserting the fixed fork tube into the slider tube, could I possibly damage the new seal when I slide the fixed fork tube into the slider tube?

 

Now on the R1250GS, they do it exactly as you have shown in your post. They remove the old seal, pour in the oil to the correct level, use a drift to tap in the new fork seal, then slide the fixed fork tube into the slider tube. This manual has no note about possibly damaging the fork seal if the fixed fork tube is pulled out of the slider tube. I found it weird that there was this difference between the two manuals.

 

Motion Pro makes this tool which slides over the fixed fork tube and can drive the seal in, as described in the R1200RT manual:

https://www.motionpro.com/product/08-0492

 

They obviously also make the bearing driver tools, which you used. This would match the procedure in the R1250GS manual:

https://www.motionpro.com/product/08-0551

 

What are your thoughts on this?

[9Mary7]

I'm probably missing something as I don't have a wethead so I'll ask. Is there something preventing y'all from the easy peasy removal of the upper fork tube while leaving all the lower parts in place? I've done it this way on other series' of RT and it literally takes no more than a half hour start to finish..... tube up and out, swap out the leaking seal, drop the male half back down thru the upper tree and into the lower leg. 

[Audi403]

Another member sent me to procedure from the R1250RT manual. The procedure is the same as the R1200RT manual. They install the fixed fork tube into the slider tube before installing the fork seal. There is the same warning about the sharp edged vent hole in the fixed fork tube damaging the fork seal if the fixed fork tube is pulled out of the slider tube past the as-installed position. I'm assuming this risk also exists if the fork seal is installed into the slide tube before the fixed fork tube is installed. It is weird that the R1250GS manual is different. 

 

Edit: Also confirmed the oil capacity is the same for the R1250RT as the R1200RT.

[Audi403]

1 minute ago, 9Mary7 said:

I'm probably missing something as I don't have a wethead so I'll ask. Is there something preventing y'all from the easy peasy removal of the upper fork tube while leaving all the lower parts in place? I've done it this way on other series' of RT and it literally takes no more than a half hour start to finish..... tube up and out, swap out the leaking seal, drop the male half back down thru the upper tree and into the lower leg. 

I haven't done the job yet, but I don't think there is anything preventing it. Just seems like it would be a lot easier to work on with it removed. My personal preference would be to spend the extra time removing it so I don't have to fight with the constricted space.

[9Mary7]

5 minutes ago, Audi403 said:

here is the same warning about the sharp edged vent hole in the fixed fork tube damaging the fork seal if the fixed fork tube is pulled out of the slider tube past the as-installed position

Plastic wrap is your friend with that issue.

[Scott9999]

3 hours ago, Audi403 said:

Hey Boxflyer,

 

Thank you for this post. I'm about to do this job on my R1250RT. I have the fork seal kit and I'm just about to purchase the correct tools for pulling the seal as well as driving the new seal in.

Being the penny-wise, pound foolish bastard that I am, I would probably try using what I have successfully used in the past:  A "slip-slip" PVC pipe connector, with a PVC pipe connecting to that, large enough to slip over the front fork.  These seals don't require much pressure to press in, as long as the force around the seal is consistent on all sides of the seal, you should have no problem.

[Audi403]

29 minutes ago, Scott9999 said:

Being the penny-wise, pound foolish bastard that I am, I would probably try using what I have successfully used in the past:  A "slip-slip" PVC pipe connector, with a PVC pipe connecting to that, large enough to slip over the front fork.  These seals don't require much pressure to press in, as long as the force around the seal is consistent on all sides of the seal, you should have no problem.

 

Yes, thank you. I believe a socket works as well. I made the post because the procedure Boxflyer used differs from the R1200RT and the R1250RT service manual. The service manual states to install the fixed fork tube into the slider tube before installing the fork seal. There is a caution about damaging the fork seal.

 

However, the R1250GS manual matches the procedure Boxflyer used. Drive the fork seal into the slider tube, and then install the fixed fork tube into the slider tube. There is no warning about damaging the fork seal. I found it unusual that BMW listed two different procedures for the same style of fork.

 

Maybe it is safest to install the fixed fork tube into the slider tube first, before installing the seal. This way there is no chance of damaging the fork seal. I ordered Motion Pro's Ringer 47mm fork seal driver which will allow for this procedure, as explained in the R1200RT and the R1250RT service manual. 

[Audi403]

So it turned out the fork seal driver tool I ordered was the wrong size. I thought 47mm would be the correct size, as that's the size of the tool Boxflyer used, and the outside diameter of the fork seal. Turns out, the tool is sized to the diameter of the forks. I should have read the description I guess lol. I believe 37mm is the correct size if anyone else buys the Motion Pro Fork Seal Driver.

 

Since I didn't have the correct tool, I followed a similar procedure to the one Boxflyer posted above. I installed the new seal before inserting the fixed fork tube into the slider tube. I used a 33mm impact socket to drive the seal in (outside diameter measures 46mm).

 

One interesting thing to note, my fork only had about 420mL of oil in it. My leak was very slow, only a drop or two of oil would seep per ride. Never enough to drip down the fork tube. Maybe it was underfilled from the factory? The manual states the fluid capacity is ~545mL, and it should measure 90mm from the top of the fork tube. It took just about exactly the volume specified to fill it to the proper level. I used Motorex Racing Fork Oil 10W (recommended by my BMW dealership)