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Chasing that notorious shift shaft oil seal leak.

birdland

Veteran Member
Joined
Oct 3, 2020
Total Posts
578
Total likes
41
Location
Osoyoos B.C. Canada
Any secrets here? I’ve gone through a lot of seals trying various tricks to get this to stop leaking. In some form or combination I have tried all these kluges at one time or another;

1) these are either oem or Cmsnl or Common Motor seals and all are 12 x 25 x 4.5

2) I’ve cleaned and touched up the shaft as much as possible with carb cleaner, 800 grit sandpaper.

3) same with the mating surface of the seat.

4) I’ve tried installing the seal flipped so that the seal ID is riding at a different spot on the shaft

5) I’ve used high temp silicone on the OD surface

6) I wrap the splines with a single layer of Teflon tape to install.

7) I’ve installed dry and lubricated with silicone or oil.

It IS the shift seal leaking - and I can find no other source of oil under the sprocket cover. It always starts slowly and then goes back to a regular drip after a couple of weeks.

I think it’s the outside of the seal that’s leaking (against the seat - not the shaft) but it’s impossible to tell.

So - suggestions?

I have two seals left before I have to order more - and I’m getting tired of going back in every couple of weeks. I’d LOVE to solve this.

Thanks in advance for any suggestions.

Now I’m gonna watch the Flames kick Dallas Stars butt - and check back in later.
 
Now I’m gonna watch the Flames kick Dallas Stars butt - and check back in later.

Well, at least you have your priorities straight. :)

As long as the shaft movement in and out doesn't allow the circlip groove to get into the seal there's only one other reason it would be leaking, and that would be the size and/or surface of the shaft itself IMO. IIRC you fashioned a method to control end play because the circlip groove was boogered up, correct me if I'm not remembering right. You shouldn't have to change the seal more than once or twice in the entire time of ownership so something isn't quite right. Maybe the inner diameter of the lower case is enlarged from the shift shaft movement over the years allowing the shaft to deflect the inner sealing edges of the seal.
 
Check the shift shaft hole in the outer cover (sprocket cover)...
If it is oval at all, the shaft is or was bent and similarly, the hole in the main cases will allow enough movement to cause leaking past the seal....

Installing a seal backwards means the "squeegie" lip of the seal is no longer being forced tighter by fluid pressure within and is counterproductive as it will leak more easily.....
 
Check the shift shaft hole in the outer cover (sprocket cover)...
If it is oval at all, the shaft is or was bent and similarly, the hole in the main cases will allow enough movement to cause leaking past the seal....

Installing a seal backwards means the "squeegie" lip of the seal is no longer being forced tighter by fluid pressure within and is counterproductive as it will leak more easily.....


Thanks Steve (and Tom)

I'll give it another shot with these things in mind.

Question - do you lube the seal when installing? And if so, what to use?
 
I generally just use light grease but motor oil works just fine too.
wait, are you asking the OD or the ID? well doesn't matter, i generally lube both.
 
Just plain motor oil will do, but I don't think that's the issue. I go with Steve, check for bended shift shaft, or ovality on the shift shaft guide. And in case of a warped cover, the holes are not aligned, this leads to wear, which leads to ovality of your shift shaft guidance.
 
Just plain motor oil will do, but I don't think that's the issue. I go with Steve, check for bended shift shaft, or ovality on the shift shaft guide. And in case of a warped cover, the holes are not aligned, this leads to wear, which leads to ovality of your shift shaft guidance.

Doug, if for some reason you do find there is a contributing issue with the sprocket cover let me know. I think I have quite a few in the parts stash.
 
Doug, if for some reason you do find there is a contributing issue with the sprocket cover let me know. I think I have quite a few in the parts stash.

Thanks Chris. Yeah - I'm pretty sure the wear on this cover isn't helping. it's really loose. I'm not sure how much that contributes, but I've tried everything else.

I got this cover a while ago because the original on the bike was cracked at the clutch adjuster. I'm sure it's not a good specimen.

I'll msg in a while. Thanks.
 
I had a CB360 (I think, too many Hondas in the past) that leaked at the clutch push rod and it was a bent push rod. I took it out and laid it on a flat concrete floor and gave it a push so it rolled slowly and I could see the bend. Just looking at it I didn't see anything. Somewhere in the past it's likely a chain broke and whacked it.
 
Any takers?

What does it say to you that this oil leak appears to be stopped after a change from 10-30 to 20-50 for the high temp months?

I mean - an oil leak is an oil leak to me. I can’t see a thicker oil not coming through a seal at very high temperatures when the thinner oil would leak at all temps. Obviously the viscosity has something to do with flow, but it’s a seal location not a shear issue or a flow issue.

I’m pleased, but puzzled.
 
Someone here mentioned a change in oil seepage after using synthetic oil in one oil change, and it stopped after he went back to using dino oil. And I'm still wondering about that one. Can't imagine a viscosity change causing a leak to completely stop.
 
Someone here mentioned a change in oil seepage after using synthetic oil in one oil change, and it stopped after he went back to using dino oil. And I'm still wondering about that one. Can't imagine a viscosity change causing a leak to completely stop.

Same. And it’s not the only thing that’s puzzling me. Onward…
 
It's easy to let your curiosity lead you down a rabbit hole. If it's not leaking just keep an eye on it and find something else to wonder about.
 
Someone here mentioned a change in oil seepage after using synthetic oil in one oil change, and it stopped after he went back to using dino oil. And I'm still wondering about that one. Can't imagine a viscosity change causing a leak to completely stop.
This was an actual problem in the 70's when synthetics were new. It had to do with some incompatibility of the rubber and the oil. Over time the oils were reformulated and that seemed to clear it up but by then the leakers had also changed the seals so it could be a combination of things.
Nothing about oil leaks surprises me anymore. I've dealt with gasket that have to be soaked in water for 8 hours before use (Rootes engines), 3 piece aluminum oil pans bolted to an aluminum engine block (Alfa Romeo), aluminum parts bolted to steel w/o any gasket ('50's Maserati), O-rings and copper wire in place of a head gasket, (MG Midget race engine 15.8:1 compression) and the list goes on.
 
after you prep to put a new seal in, run a q tip around the outer side of where the seal will sit, run it all over and then look for where it pulls. if there is a burr in there or on the outer edge I imagine it could split the seal and that could cuase it to leak. just a wild guess, but I don't think it is common for the outer edge to leak, usually they eventually wear out and leak aroudn the shaft. maybe the seals are just junk. a pack of OEM honda seals isn't really going to break the bank.
 
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