Strange metal rear main seal

[lewisnort]

This is a K1100 LT 1998 and I’m chasing down an oil leak from the weeping hole under the transmission before I completely re do the entire bike, bought a replacement rear main seal, clutch bolts, oring the lot. But then I came to remove the rear main seal after taking the clutch carrier out and the replacement looks nothing like the one that’s already in there. It has this worn metal outer shell with worn through text on (no it’s not dirt I’ve wiped it off it’s worn down). My replacement one has no such metal shell, just the rubber. What do I do!

[Laitch]

There are two types of main seal. One has a spring around the interior perimeter. That is the earlier type and likely what is in your photo. The later type is a teflon composition seal with no spring. It is illustrated in the photos below. The coloration could vary among manufacturers and production years. This seal is not soaked in oil before mounting. The portion fitting over the shaft must be stretched wider to fit easily over the shaft; many use pill containers for this purpose.



A seal puller—a hook-shaped tool—is the best tool used to yank the old seal out of its position although folks have used—or unsuccessfully used—any tool they believed could pry the seal out of its position without damaging the surfaces to be sealed. Installation instructions abound on this site and others. Here's a link to some concise explanation.

There is also an o-ring on the shaft that needs replacing. Don't neglect doing that.

[lewisnort]

Thank you very much, the teflon (now I know) seal from motorworks seems to already come with a plastic ring much like a segment of a pill bottle on the inside, I had wondered what that was for. Already got myself a seal puller ready and a shaft o ring. That o ring was what was causing me so much pain trying to get the clutch carrier out, ended up fishing it out over the course of an hour with some hooks.

This is my first time I’m anywhere near the inside of an engine so I’m very grateful for such helpful advice.

[Laitch]

To be clear, there is metal beneath the face of the teflon seal. The damaged seal now seem suspiciously like a teflon-style seal, judging from the ribs around its interior sealing surface; regardless, clean and inspect all sealing surfaces before installation. Carefully follow the instructions at the link in Reply #1. What are you using as an assembly reference?

[The Mighty Gryphon]

Looks like the clutch basket has been rubbing on the face of the seal.  Something isn't right.

I see the seal is standing proud of the engine case.  Maybe it wasn't installed properly and left too far out of the case.

I have used a piece of cardboard from a cereal box with a hole that is a bit larger than the seal glued to a piece of wood.  I drive the seal in with the wood, the cardboard thickness keeps the seal for going in flush, with the correct 0.5mm exposure.

[Scott_]

I agree with TMG, in that the existing seal looks like it wasn't installed quite deep enough.
Yes it is supposed to set 'proud' of the block but it looks like it was left too far out.
There is a TSB that give the specific amount of distance for the seal installation.  0.5mm as TMG noted.

https://www.motobrick.com/index.php?topic=4993.0

[lewisnort]

To be clear, there is metal beneath the face of the teflon seal. The damaged seal now seem suspiciously like a teflon-style seal, judging from the ribs around its interior sealing surface; regardless, clean and inspect all sealing surfaces before installation. Carefully follow the instructions at the link in Reply #1. What are you using as an assembly reference?

I'm using the workshop manual as an assembly reference as well as various videos on youtube, I couldn't find a specifically Chris Harris one for this.

[lewisnort]

I agree with TMG, in that the existing seal looks like it wasn't installed quite deep enough.
Yes it is supposed to set 'proud' of the block but it looks like it was left too far out.
There is a TSB that give the specific amount of distance for the seal installation.  0.5mm as TMG noted.

https://www.motobrick.com/index.php?topic=4993.0

It definitely sits further proud than 0.5mm so that would make sense, there's a lot of questionable work on this bike so I'm not too impressed with the garage that the previous owner says they always took it to, and there's also some wear on the spring plate around the edge that connects to the friction disk, not sure how common this is I'll try and get pictures sometime soon.
I may be able to get that tool produced at work and try out that cereal box trick too. (I've put off changing the seal since this did hit my confidence somewhat)
Thanks again everyone the best part about these bikes are the people around them

[lewisnort]

There are two types of main seal. One has a spring around the interior perimeter. That is the earlier type and likely what is in your photo. The later type is a teflon composition seal with no spring. It is illustrated in the photos below. The coloration could vary among manufacturers and production years. This seal is not soaked in oil before mounting. The portion fitting over the shaft must be stretched wider to fit easily over the shaft; many use pill containers for this purpose.



A seal puller—a hook-shaped tool—is the best tool used to yank the old seal out of its position although folks have used—or unsuccessfully used—any tool they believed could pry the seal out of its position without damaging the surfaces to be sealed. Installation instructions abound on this site and others. Here's a link to some concise explanation.


There is also an o-ring on the shaft that needs replacing. Don't neglect doing that.

I'm just looking at the diagram again in your post and noticeably missing on my bike is the stop disk, number 10 on the diagram part number 11211460873, could this be causing the wear on the rear main? Not even sure where I would get a decent replacement, motorworks only has used examples.
Would this be the same as part labelled 1 in the screenshot, it seems a lot thicker, though that could be artistic interpretation I'm sure.

Screenshot 2025-02-26 090747.png (78.17 kB . 595x426 - viewed 268 times)

This from real OEM lists 2 numbers for the stop disk, a 1mm and a 1.25 is there a noticeable difference as motorworks if I do order from there only carry the 1mm.

Screenshot 2025-02-26 090957.png (45.14 kB . 497x576 - viewed 259 times)

[Laitch]

This from real OEM lists 2 numbers for the stop disk, a 1mm and a 1.25 is there a noticeable difference as motorworks if I do order from there only carry the 1mm.

Drawings of parts in the fiche are not drawn to scale so don't worry if things look thicker or thinner.

As far as a 1mm disc and a 1.25mm disc having a noticeable difference between them, the answer is Yes; the difference is 0.25mm. That difference can possibly mean the difference between the clutch carrier rubbing on the seal face or not rubbing.

We'll never know how well the seal was handled and installed. I cannot find information about which disc is used. The choice may be made during assembly at the factory to accommodate variance in part dimensions. The assembly instructions for us plebians indicate to measure the old disc and replace it with the same size. Clearly, if you use the disc with the greater thickness, the cover end of the clutch cover shaft will be 0.25mm further from the seal if the original disc was 1mm thick.

[lewisnort]

The assembly instructions for us plebians indicate to measure the old disc and replace it with the same size. Clearly, if you use the disc with the greater thickness, the cover end of the clutch cover shaft will be 0.25mm further from the seal if the original disc was 0.1mm thick.

Given that its entirely missing on mine I'll have to go with the motorworks 1mm and hope

[Laitch]

If the clutch carrier was assembled to the output shaft without the stop disc, installing the 1mm disc could be considered an improvement. Onward!