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Discussion Starter · #1 ·
I've enjoyed the company so far and thought I'd give back. I've been struggling with a leaky oil seal since I got my 2021 GS (02/21 build if that matters). About 250 miles in I see some oil dripping down the side of the engine, enough that it drips on my garage floor after every ride. I saw that it was coming from the oil seal but couldn't believe it with a bike so new. I figured out that the bike was overfilled by a good amount so I chalked it to over pressurization. Changed the oil, filled it to the correct level and thought that was it.

Well, no such luck. I started with the dealer but since they were a pain to deal with plus would take a week to even look at the bike, I instead picked up the original part from them and got to work.

Leaky original seal


For those attempting this, the seal is a 20-min swap (if that) using the screw and slide hammer trick. No damage and pops off like a champ. Harbor Freight has the slide hammer for 26 bucks here. I punched, not drilled the pilot hole to prevent shavings. Done properly you will not scar any portion of any part of the bike.

Pop goes weasel


I greased the replacement part (like a good mechanic should) so it didn't start it's life dry, slid it in carefully with my home-made seal driver (details below), put the bike together and went on my merry way thinking that was it. I checked after every ride just to make sure and though it stayed dry for a while, lo and behold I see this after about 250 miles. Same fate and failure mode & miles as the original seal.

Second leaky seal


Well ok, not cool. So looks like I needed to get deeper into this. Fine, I don't mind a challenge. One avenue I though I'd explore is that I noticed the seals I pulled off didn't "bounce back" when I put my nail to it. Meaning if I rolled my nail across it, the rubber would permanently deform. You'll see the lines along the face of the seal in one of the pictures below. So if it was indeed a manufacturing defect I figured I'd source a suitable replacement from a different manufacturer and rule that out. No OEM exists for this part but thankfully them Germans love to document and the dimensions were on realoem, plus molded into the part itself. A 25 x 52 x 7 oil seal. All that was left was the choice of material. Factory (as molded on original seal) was Simriz Z134.

I was able to source two dimensionally-identical replacements with material properties suitable for the task. Both are from SKF, sourced from my favorite industrial supplier. One uses Nitrile, one uses FKM (or more commonly known as Viton). I bought both but put on the Nitrile first. I know most of you would jump to the "superior" material that is FKM/Viton first but let's not forget that Nitrile exists and is still popular in industrial applications for a reason. Whatever it lacks in extreme high-temp and chemical resistance against FKM it makes up in abrasion and tear resistance. The shaft sealing surface was perfect but I thought a "beefed up" sealing edge material couldn't hurt.

SKF 25x52x7 HMSA10 RG (Nitrile)


SKF 25x52x7 HMSA10 V (FKM/Viton)


That beautiful Viton brown...


Output shaft


So here are a few comparison shots. Sadly the BMW part seemed like a poorly made part by comparison. The overmolding quality was poor and even felt cheap. Quantitatively speaking the BMW part was 2 grams lighter than the SKF part, assuming that means anything. Also if you look closely, you'll see the parts where I rolled my nail over the oil seal. I'll make these pictures slightly bigger so they're easier to see.

Front: BMW on the left, SKF on the right


Back: BMW on the left, SKF on the right


So finally, RESULTS. I waited a while to put some miles on the seal in various conditions before I posted this. I'm happy to report it's been around 700 miles and no leaks. Today was the most punishing of my tests, where because of high ambient temps and bad traffic I had the fan kicking on and off. Then cycled between that and cruising at 75mph for long distances, about 250 miles altogether.

I'll update this thread if/when it leaks again. It's a BMW after all, so I know that's just a matter of time (own/ed 5 to date). That said I've loved them all, the baby GS the latest one, oil shaft seal notwithstanding.

Oh, the seal driver. You can make one for about a buck and a half using a PVC pipe reducer. Soft enough that it doesn't damage the shaft or the transmission casing but strong enough to tap the seal in. The pipe reducer engages perfectly and I wouldn't have dimensioned it differently even if I had a lathe handy. It's the one with 2" OD and 1" ID.

Home Depot seal driver


Seal driver with seal


Happy Motoring, folks!

Paolo
 

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I've enjoyed the company so far and thought I'd give back. I've been struggling with a leaky oil seal since I got my 2021 GS (02/21 build if that matters). About 250 miles in I see some oil dripping down the side of the engine, enough that it drips on my garage floor after every ride. I saw that it was coming from the oil seal but couldn't believe it with a bike so new. I figured out that the bike was overfilled by a good amount so I chalked it to over pressurization. Changed the oil, filled it to the correct level and thought that was it.

Well, no such luck. I started with the dealer but since they were a pain to deal with plus would take a week to even look at the bike, I instead picked up the original part from them and got to work.

Leaky original seal


For those attempting this, the seal is a 20-min swap (if that) using the screw and slide hammer trick. No damage and pops off like a champ. Harbor Freight has the slide hammer for 26 bucks here. I punched, not drilled the pilot hole to prevent shavings. Done properly you will not scar any portion of any part of the bike.

Pop goes weasel


I greased the replacement part (like a good mechanic should) so it didn't start it's life dry, slid it in carefully with my home-made seal driver (details below), put the bike together and went on my merry way thinking that was it. I checked after every ride just to make sure and though it stayed dry for a while, lo and behold I see this after about 250 miles. Same fate and failure mode & miles as the original seal.

Second leaky seal


Well ok, not cool. So looks like I needed to get deeper into this. Fine, I don't mind a challenge. One avenue I though I'd explore is that I noticed the seals I pulled off didn't "bounce back" when I put my nail to it. Meaning if I rolled my nail across it, the rubber would permanently deform. You'll see the lines along the face of the seal in one of the pictures below. So if it was indeed a manufacturing defect I figured I'd source a suitable replacement from a different manufacturer and rule that out. No OEM exists for this part but thankfully them Germans love to document and the dimensions were on realoem, plus molded into the part itself. A 25 x 52 x 7 oil seal. All that was left was the choice of material. Factory (as molded on original seal) was Simriz Z134.

I was able to source two dimensionally-identical replacements with material properties suitable for the task. Both are from SKF, sourced from my favorite industrial supplier. One uses Nitrile, one uses FKM (or more commonly known as Viton). I bought both but put on the Nitrile first. I know most of you would jump to the "superior" material that is FKM/Viton first but let's not forget that Nitrile exists and is still popular in industrial applications for a reason. Whatever it lacks in extreme high-temp and chemical resistance against FKM it makes up in abrasion and tear resistance. The shaft sealing surface was perfect but I thought a "beefed up" sealing edge material couldn't hurt.

SKF 25x52x7 HMSA10 RG (Nitrile)


SKF 25x52x7 HMSA10 V (FKM/Viton)


That beautiful Viton brown...


Output shaft


So here are a few comparison shots. Sadly the BMW part seemed like a poorly made part by comparison. The overmolding quality was poor and even felt cheap. Quantitatively speaking the BMW part was 2 grams lighter than the SKF part, assuming that means anything. Also if you look closely, you'll see the parts where I rolled my nail over the oil seal. I'll make these pictures slightly bigger so they're easier to see.

Front: BMW on the left, SKF on the right


Back: BMW on the left, SKF on the right


So finally, RESULTS. I waited a while to put some miles on the seal in various conditions before I posted this. I'm happy to report it's been around 700 miles and no leaks. Today was the most punishing of my tests, where because of high ambient temps and bad traffic I had the fan kicking on and off. Then cycled between that and cruising at 75mph for long distances, about 250 miles altogether.

I'll update this thread if/when it leaks again. It's a BMW after all, so I know that's just a matter of time (own/ed 5 to date). That said I've loved them all, the baby GS the latest one, oil shaft seal notwithstanding.

Oh, the seal driver. You can make one for about a buck and a half using a PVC pipe reducer. Soft enough that it doesn't damage the shaft or the transmission casing but strong enough to tap the seal in. The pipe reducer engages perfectly and I wouldn't have dimensioned it differently even if I had a lathe handy. It's the one with 2" OD and 1" ID.

Home Depot seal driver


Seal driver with seal


Happy Motoring, folks!

Paolo
Good job! Excellent description. I hope I'll never need it.
 

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I've enjoyed the company so far and thought I'd give back. I've been struggling with a leaky oil seal since I got my 2021 GS (02/21 build if that matters). About 250 miles in I see some oil dripping down the side of the engine, enough that it drips on my garage floor after every ride. I saw that it was coming from the oil seal but couldn't believe it with a bike so new. I figured out that the bike was overfilled by a good amount so I chalked it to over pressurization. Changed the oil, filled it to the correct level and thought that was it.

Well, no such luck. I started with the dealer but since they were a pain to deal with plus would take a week to even look at the bike, I instead picked up the original part from them and got to work.

Leaky original seal


For those attempting this, the seal is a 20-min swap (if that) using the screw and slide hammer trick. No damage and pops off like a champ. Harbor Freight has the slide hammer for 26 bucks here. I punched, not drilled the pilot hole to prevent shavings. Done properly you will not scar any portion of any part of the bike.

Pop goes weasel


I greased the replacement part (like a good mechanic should) so it didn't start it's life dry, slid it in carefully with my home-made seal driver (details below), put the bike together and went on my merry way thinking that was it. I checked after every ride just to make sure and though it stayed dry for a while, lo and behold I see this after about 250 miles. Same fate and failure mode & miles as the original seal.

Second leaky seal


Well ok, not cool. So looks like I needed to get deeper into this. Fine, I don't mind a challenge. One avenue I though I'd explore is that I noticed the seals I pulled off didn't "bounce back" when I put my nail to it. Meaning if I rolled my nail across it, the rubber would permanently deform. You'll see the lines along the face of the seal in one of the pictures below. So if it was indeed a manufacturing defect I figured I'd source a suitable replacement from a different manufacturer and rule that out. No OEM exists for this part but thankfully them Germans love to document and the dimensions were on realoem, plus molded into the part itself. A 25 x 52 x 7 oil seal. All that was left was the choice of material. Factory (as molded on original seal) was Simriz Z134.

I was able to source two dimensionally-identical replacements with material properties suitable for the task. Both are from SKF, sourced from my favorite industrial supplier. One uses Nitrile, one uses FKM (or more commonly known as Viton). I bought both but put on the Nitrile first. I know most of you would jump to the "superior" material that is FKM/Viton first but let's not forget that Nitrile exists and is still popular in industrial applications for a reason. Whatever it lacks in extreme high-temp and chemical resistance against FKM it makes up in abrasion and tear resistance. The shaft sealing surface was perfect but I thought a "beefed up" sealing edge material couldn't hurt.

SKF 25x52x7 HMSA10 RG (Nitrile)


SKF 25x52x7 HMSA10 V (FKM/Viton)


That beautiful Viton brown...


Output shaft


So here are a few comparison shots. Sadly the BMW part seemed like a poorly made part by comparison. The overmolding quality was poor and even felt cheap. Quantitatively speaking the BMW part was 2 grams lighter than the SKF part, assuming that means anything. Also if you look closely, you'll see the parts where I rolled my nail over the oil seal. I'll make these pictures slightly bigger so they're easier to see.

Front: BMW on the left, SKF on the right


Back: BMW on the left, SKF on the right


So finally, RESULTS. I waited a while to put some miles on the seal in various conditions before I posted this. I'm happy to report it's been around 700 miles and no leaks. Today was the most punishing of my tests, where because of high ambient temps and bad traffic I had the fan kicking on and off. Then cycled between that and cruising at 75mph for long distances, about 250 miles altogether.

I'll update this thread if/when it leaks again. It's a BMW after all, so I know that's just a matter of time (own/ed 5 to date). That said I've loved them all, the baby GS the latest one, oil shaft seal notwithstanding.

Oh, the seal driver. You can make one for about a buck and a half using a PVC pipe reducer. Soft enough that it doesn't damage the shaft or the transmission casing but strong enough to tap the seal in. The pipe reducer engages perfectly and I wouldn't have dimensioned it differently even if I had a lathe handy. It's the one with 2" OD and 1" ID.

Home Depot seal driver


Seal driver with seal


Happy Motoring, folks!

Paolo
Great read my friend. Thank you. As said before. Hope i don't need to follow your directions.
 

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Discussion Starter · #4 ·
Thanks, guys. My guess is a bad batch of seals, nothing more. But it's good to know we have alternatives. Amazon carries one by National which I think is a Timken brand, and so does Oreilly's.
 
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