'78 GS750EC: replacing countershaft oil seal

[Himble]

Hi folks, I've identified my recent left side oil leak as coming from the countershaft oil seal.
I have replacements on the way (OEM) for the seal, the 1 x 24.5mm O-ring, the C-ring and also the shift shaft oil seal to replace while I've got the cover off.

My question: I have searched the forum and a couple of posts have suggested that the case needs to be split to remove/replace the countershaft seal.
Is this right? If this is the case, then why have the C-ring in place? Seeking the "proper" answer before I proceed.
TIA
Andy
EDIT: pic added to show seal and C-ring.

[uk gs nut]

I don't think you will get the C ring out without splitting the cases.

[John Park]

I don't think you will get the C ring out without splitting the cases.

I'd think that you could cut a notch in the top of the C with a Dremel and drill two holes in the ends and then squeeze it inwards to collapse it. A small cut into the casting wouldn't be a worry as it's just there to hold the C. Once out, the new seal could be installed with silicone to help retain it. The ring is there to keep crankcase pressures from pushing it out.

Unless you have a lot of blowby or a plugged breather in the valve cover, I doubt the pressure would ever rise enough to be problematic. That said, there are a few bikes that made a habit of popping that seal, but they were singles that had a large crankcase pressure fluctuations that just don't happen when you pistons heading opposite direction.

If you're really worried, it might be possible to find an appropriate snap ring to fit in the groove once you've trimmed it to a half circle.

[Himble]

I'd think that you could cut a notch in the top of the C with a Dremel and drill two holes in the ends and then squeeze it inwards to collapse it. A small cut into the casting wouldn't be a worry as it's just there to hold the C. Once out, the new seal could be installed with silicone to help retain it. The ring is there to keep crankcase pressures from pushing it out.

Unless you have a lot of blowby or a plugged breather in the valve cover, I doubt the pressure would ever rise enough to be problematic. That said, there are a few bikes that made a habit of popping that seal, but they were singles that had a large crankcase pressure fluctuations that just don't happen when you pistons heading opposite direction.

If you're really worried, it might be possible to find an appropriate snap ring to fit in the groove once you've trimmed it to a half circle.

Hi John, I was discussing this very approach with a colleague yesterday! Thanks for posting.
It strikes me as being a bit silly to have to split the cases (and all the extra work that entails!) just to replace one oil seal.

[Jhurt]

I’ve got my cases apart right now (same bike and motor) for a rebuild/cleanup etc so I’m looking at this seal...I’d definitely try the method described above and find a snap ring to replace the c clip. Worst case you still have a leak and your’re only out an hour or two. How bad is the leak exactly? Leaks drive me batty so I’d have to sort it but maybe you could live with it if it’s not bad. If you get the parts in advance you could do the full tear down and reassembly in a weekend

[Himble]

OK I've successfully removed the C-clip and seal without splitting the case by basically following John Park's suggestion above.
I drilled a 2mm hole at each end of the C-clip, and a 3rd hold at the top of the clip. I then widened the top hole with a 3.5mm bit.
I prised the RHS end of the clip up a bit with a small flat blade screwdriver. The hole previously drilled made it easier to bend the clip at the end.
I then used a pair of strong needle-nose pliers, expecting that it would be a battle to pull the clip out, but in fact it was very easy.
With the clip removed, it was now straightforward to remove the countershaft seal.
The new seal will be inserted tomorrow.

Pic shows the removed clip with the drilled holes, and the removed seal.

[748cc]

That's great, Andy - You did it!!

One goofy question: Does that clip channel around both the front & back sides of the seal, or just rest in front of it? Sorry for my ignorance, just invisioning the assembly too deeply perhaps.

Congrats again, Andy!

[hannibal]

I believe it only goes on the outside of the seal.

[Himble]

Yep, just the outside.
I have a new C-clip but not sure whether I'll be able to fit it. As suggested earlier, I'll see if I can chase up a half-round circlip or a snap ring of the right size.

[Himble]

OK with a bit of push and shove, the new C-ring is in place! No more oil leaks!!

[steve murdoch]

Thanks for the photo and the follow-up, Andy.
Glad you got it sorted.

[suziscrambler]

Hi Himble, thanks for the useful tip. Can you please share the part numbers for your items you ordered:
"1 x 24.5mm O-ring, the C-ring and also the shift shaft oil seal "

Thank you !

[Himble]

Hi mate, have sent you PM. Sorry for late reply!

Hi Himble, thanks for the useful tip. Can you please share the part numbers for your items you ordered:
"1 x 24.5mm O-ring, the C-ring and also the shift shaft oil seal "

Thank you !