Leaking from the O-ring on the Clutch pushrod. Solutions please!

[Unk Tantor]

I've got a big oil leak from the rear of the gearbox. I have put a new O ring on during the bikes rebuild, about 2,000 miles and one year ago, it was leaking like this from the get go.I have tried to search here to look at other routes to fix this issue other then a standard o ring replacement but to no avail.I do recall seeing some picture on a thread that showed wear (or was it a porous casting issue?)on the casing itself. I would be grateful for advice on how to address this . Do I need a larger spec O ring or does the case need to be treated in some way?
Cheers

[fotoguzzi]

did you forget the conical seals (2) that fit the pushrod inside the tranny?

#7 below

[Unk Tantor]

Hi Fotoguzzi. The cone seals were replaced as well.

[Chuck in Indiana]

Many have had better luck with a stack of o rings rather than the conical seals. <shrug> Dunno. At least it's simple to get to and have a look.

[Vasco DG]

The pushrod seals seal, surprisingly, the pushrod! They prevent oil scrolling down the rod into the clutch area which is supposedly dry. They do nothing for preventing oil getting from the thrust mechanism area, which is thankfully wet, to the outside world.

If it's dribbling from the thrust mushroom and you are certain that the o-ring has the correct section then chances are the tunnel in the end case the mushroom and seal run in in the case is compromised. Answer would be to refurbish the tunnel in the endcase and use a slightly larger section o-ring.

Pete

[Unk Tantor]

I was thinking, if it was wear on the endcase tunnel, to remove the swingarm(obviously to examine it) and to lightly coat the area were the seal contacts with expoxy resin (or a smear of JB weld ) gently smooth with wet&dry in the hope of creating a  smoother contact surface.
Is this bodgery to a high idiot scale?
 Do I need to remove the endcase and get a shop to machine it out and insert some sort of liner?
Or should I just see if I can buy another endcase?

[Chuck in Indiana]

I really don't think your epoxy bodge would work. <shrug>  ;D

[Wayne Orwig]

I was thinking, if it was wear on the endcase tunnel, to remove the swingarm(obviously to examine it) and to lightly coat the area were the seal contacts with expoxy resin (or a smear of JB weld ) gently smooth with wet&dry in the hope of creating a  smoother contact surface.
Is this bodgery to a high idiot scale?

You can be sure I would try this. I just wouldn't tell anyone.  :BEER:
The really big issue is degreasing it so it works well. And you need to do everything without contaminating the bearing.


I noticed in the photo, it looks like the plunger is deep in the case. Is there normal?
 

[Unk Tantor]

I noticed in the photo, it looks like the plunger is deep in the case. Is there normal?
 

its got a new flywheel and deep spline clutch on it, it did need the plunger adjusted deep to get everything to get the clutch to disengage.
Not sure why.

[Warwick in NZ]

 Do I need to remove the endcase and get a shop to machine it out and insert some sort of liner?
 

This sounds good, really the only way....did it for my monza, the casting was like swiss cheese, all good now...Warwick :)

[acogoff]

    This o'ring is easily replaced by pulling the arm off and pulling the plunger. The #115 buna oring goes tits up on my T3 every couple of years. I now have on hand a buna X'ring of the same number to try the next go 'round.  Before getting into the remachining mode I would simply try wrapping a round of thin cut electrical tape under the o'ring to shim it out a few thousandths.

[racasey]

Replacing an O-Ring with a Quad-Ring is the industry wide solution to this problem.  Quad-Rings double the sealing surfaces and have greater wear before failure than a standard O section rings.

I'm unable to post an image of a Quad-Ring, so kindly Google Quad ring and make your selection.

Ciao,
Dick

[Rolf Halvorsen]

The article number for this O-ring is 90706170 and the dimension is Ø17,12 x 2,5mm.

I have had success with thicker O-rings. Ø17 x 2,7mm or Ø17 x 2,8mm. I even may have Ø17 x 2,9mm.

I can send you some of these larger O-rings, but you have to wait 2 weeks (I am not at home now.).

This is an easy fix for a start. Whenever I restore gearboxes, I restore the diameter which is Ø22,0mm from the start. Old boxes destroys the perfect roundness - so I machine this hole to a larger diameter for example Ø22,2mm together with a larger O-ring wall thickness.

I hope this could be of help for you.

Rolf

[acguzzi]

is it possible it is too far in? you say it is not where it was before, you could try to shim the pushrod by putting a small piece of steel inside the mushroom, just be careful the shim doesnt fall in.

[pehayes]

O-rings require a specific amount of 'crush' to make them oval in cross section and create a seal.  Generally 10% to 15%.  If the transmission was on the bench, I'd pull the back cover and redo a sleeve insert to restore original dimension.  If the transmission is on the bike, I'd be tempted to use my lathe and fabricate another, nearly-duplicate outer plunger body.  Its just a cylinder with a recess in the front and stem in the back and a groove for the ring.  By measuring carefully, I would cut the o-ring's groove in the outer body to a shallower depth which would force a more significant crush on the new o-ring.  That process is certainly easier and quicker than dismantling the entire transmission.  If it still fails you haven't lost much time in the effort.  I'll see if I can go dig up an outer body and measure the factory groove and recommend an alternate/shallower groove depth.

Patrick Hayes
Fremont CA

[pehayes]

OK, so I dug out a throwout outer body from an old V50.  It is the same part number as used on the big block 5-speed transmission.  The o-ring groove on this outer body is 0.153" wide by 0.090" deep.  Woefully inadequate.  This will produce about 8% squish to the OD of the standard part o-ring.  To make a good seal, I'd like to see more like 15% to 18% squish.  I propose that making a substitute outer body with a narrower/shallower ring groove would improve the squish characteristics dramatically.  Offhand I'd recommend 0.125" width and 0.085" depth for the o-ring groove.  Of course, if the bore of your rear cover is dramatically scarred or has casting porosity, the extra squish is now going to cause extra contact pressure and exacerbate the wear on the rubber ring and it might tear or leak even sooner.  Its a crap shoot.  Can you evaluated the quality of the bore surface?  Yes, it should eventually be done right by sleeving the bore, but a few hours to pull the swingarm and replace the o-ring several times over several years seems like a reasonable labor compromise.  I'd be happy to fabricate the modified version of the outer body.  Simple lathe task.  Let me know.

Do a google search for o-ring dimensions and you'll see lots of information about relative squish percentages for various spinning and sliding o-ring applications.

Patrick Hayes
Fremont CA

[jacksonracingcomau]

I've put two o rings in there before, just ones I had lying about, suggestions above re alternative sizes should work too.
Is very low pressure area so doesn't need much to seal it, assembling dry might tear it though.

If bore is worn there, another shim on thrust washer will give it new area to work on, easier than fitting sleeve and of course clutch wear will bring it further back, next job should be removing shim, a long way down the road

[Unk Tantor]

Thanks for all the offers and suggestions. think I'll start by replacing or doubling up seal. If the tunnel looks too badly worn then I'll consider a visit to the machinist this winter!