Crank Oil Seal leak

Onder · Nov 6, 2014

I have a persistent oil leak at the primary side crank seal. Mentioned this a few months ago and Jim suggested installing the seal with JB Weld along the outside edge. Did this and no joy. There is nothing obviously wrong with the crank surface.
Fact is it would be of no concern normally but Im running a dry belt so this why Im aware of it.
Jim's crank vent installed.
It isnt a lot of oil but it builds up. Is it possible to cure this?

Nater_Potater · Nov 6, 2014

Onder said:
Mentioned this a few months ago...

Please post a link to the prior thread. Hopefully, this will help avoid a lot of redundant question/answer sessions.

After the seal, my first thought is the three mounting bolts, but there I go with the redundant questioning...

Nathan

Onder · Nov 6, 2014

Leak is from seal to inside of primary case. No leak external of this.
Jim had mentioned the leak can be around the outer rim of the metal seal.
Ive pooped it in with JB Weld so the leak surely seems to be past the rubber lip.

cjandme · Nov 6, 2014

Onder said:
Leak is from seal to inside of primary case. No leak external of this.
Jim had mentioned the leak can be around the outer rim of the metal seal.
Ive pooped it in with JB Weld so the leak surely seems to be past the rubber lip.

You might have gotten a messed up or defective one from the get go, or it might possibly have been damaged upon installation. Just what comes to mind off the top of my head at the moment, might be neither of those though, gotta take it off and have another go at it to find out for sure I suppose.

Onder · Nov 6, 2014

Engine is fresh overhaul. A few hundred miles on original seal. This seal has about 500 miles on it.
Both seals were carefully installed.
Puzzling.

comnoz · Nov 6, 2014

Things that come to mind:

Insufficiently vented oil tank, the oil tank vent must be large enough that the tank builds no pressure.

Kinked or restricted line from my breather to the tank.

Damaged seal surface on the crank.

Damage to the seal by sliding it over an unprotected crank keyway.

Excess blowby can overwhelm the breather. Do a compression test or better yet a leakdown test. Leakage could be by damaged rings, scored cylinder or a head gasket that is leaking into a pushrod tunnel.

Does it seem to leak when running or when parked long enough to wet sump?
Are you using the seal with the steel outer shell or the rubber encased seal? Jim

Onder · Nov 6, 2014

Engine has great compression but Ill pressurize the cylinders and listen for blow by.
The oil tank vent line is standard but not plumbed to the air filter box but just
to the atmosphere. No oil dribbles from it.

Seal is steel type, installed with scotch tape on the crank.
Exhaust line of your valve is clear and not kinked. You can
feel the difference in kicking it after you run it as the
sump is pumped out by the valve.

Doesnt use oil nor is the oil dirty quickly. Plugs very clean.

Ill report back tomorrow.

Dances with Shrapnel · Nov 6, 2014

Onder said:
Seal is steel type, installed with scotch tape on the crank.

Can residual tape or adhesive knacker up the seal/seal surface?

Is this a side hack application?

Hobot · Nov 6, 2014

Ugh, does not compute unless crank bent to wiggle seal to weep or some how seal fouled on install or faulty out the box. Maybe clean off and try a spitz of those spray can seal everything wonders. I have goofed on a big lawn mower crank seal by seating it past its best position so had to destroy it to get another in with less gusto and manual reading. Don't think ya can seat Cdo seal too far in.

Torontonian · Nov 6, 2014

Try the rubber surround type seal they work for me. They don't last many years though (8-10). I use Motoseal 1 on the outer and very little of it. Even the smallest nick at seal lip to crank end equals leakage. Perhaps tapped in with too sharp a tool ? I use a drift of round flat tip-head. Judicious tapping to seat home. Getting it out another matter. :|

kerinorton · Nov 6, 2014

hobot said:
Ugh, does not compute unless crank bent to wiggle seal to weep

That crank would have to be so bent that the engine would blow to bits on the first outing, I would have thought. My seal leaks as well on my 850, but I have not touched the lower end of this bike yet so don't know what is there. I don't intend looking in a hurray either until something demands the removal of the primary drive. Extra lube on my primary chain is ok. Means the primary gets a flush out after every long run.
Dereck

comnoz · Nov 6, 2014

Onder said:
Engine has great compression but Ill pressurize the cylinders and listen for blow by.
The oil tank vent line is standard but not plumbed to the air filter box but just
to the atmosphere. No oil dribbles from it.

Seal is steel type, installed with scotch tape on the crank.
Exhaust line of your valve is clear and not kinked. You can
feel the difference in kicking it after you run it as the
sump is pumped out by the valve.

Doesnt use oil nor is the oil dirty quickly. Plugs very clean.

Ill report back tomorrow.

Well it sounds like you did everything right. Maybe you should remove my valve and make sure it is operating correctly. Maybe a reed has some debris in it or isn't seated right. You should be able to blow through it freely from the engine side. They normally vibrate like a reed instrument. There should be little if any leakage when blowing from the oil tank side. Jim

comnoz · Nov 6, 2014

Dances with Shrapnel said:
Onder said:

Seal is steel type, installed with scotch tape on the crank.

Click to expand...

Can residual tape or adhesive knacker up the seal/seal surface?

Is this a side hack application?

I would think that if it were residual tape causing a problem that it would take care of itself pretty quickly. Jim

B+Bogus · Nov 7, 2014

Torontonian said:
Try the rubber surround type seal they work for me. They don't last many years though (8-10). I use Motoseal 1 on the outer and very little of it. Even the smallest nick at seal lip to crank end equals leakage. Perhaps tapped in with too sharp a tool ? I use a drift of round flat tip-head. Judicious tapping to seat home. Getting it out another matter. :|

+1 on changing to a rubberised seal - the steel jacketed ones aren't brilliant and I won't use them any more.
The old seals come out all too easily with a couple of self-tapping screws and a pair of pliers.

My Combat (Mike's XS breather + case mods) was making a real mess with the primary case leaking oil in a big way until I replaced the crank seal as above - problem solved.

Fast Eddie · Nov 7, 2014

At the risk of sounding provoking (not my intention at all, but this is the interne tafter all) I would urge you to keep in mind that these seals DO work when all is well. Therefore you have something wrong with yours somewhere, so in answer to your question, yes, it can be fixed... you've just got to find whats wrong!

On top of the other good suggestions... are you sure its the seal thats leaking? the bolts that secure the primary case to the crankcase are known leak points. Also (and I hope this is not the case) a cracked crankcase can sometimes show itself first as an oil leak. Then there is the possibility that it is gearbox oil, coming in via the mainshaft.

Whatever the cause turns out to be, I hope you find it soon, and pleae do keep us all posted as to what you find.

JimC · Nov 7, 2014

My Combat (Mike's XS breather + case mods) was making a real mess with the primary case leaking oil in a big way until I replaced the crank seal as above - problem solved.

I'm curious as to how the XS breather and case mods was making a real mess. Could you explain, please?

tomspro · Nov 7, 2014

B+Bogus said:
+1 on changing to a rubberised seal - the steel jacketed ones aren't brilliant and I won't use them any more.
The old seals come out all too easily with a couple of self-tapping screws and a pair of pliers.

My Combat (Mike's XS breather + case mods) was making a real mess with the primary case leaking oil in a big way until I replaced the crank seal as above - problem solved.

And maybe a lead on where to get this mythical rubber main seal. :mrgreen:

comnoz · Nov 7, 2014

The steel shell seal has the capability to hold perfectly. I have used 100's of them. The chaincase on my bike was dry as a bone after returning from my fall trip.

My experience with the rubber seal has been they seal fine but, get hard as a rock after a few years.

The steel cased seal seems to handle the temperature better but it does require a good glue to seal the OD.

I think RGM has the rubber seals available. Jim

Dances with Shrapnel · Nov 7, 2014

comnoz said:
I would think that if it were residual tape causing a problem that it would take care of itself pretty quickly. Jim

Well the seal (or something) is leaking and Onder needs to try something. I suppose if the crank seal surface is oiled there would likely be no holdback of tape or mastic but if there were I would not move forward with the build knowing there's a wad of something on or immediately behind the seal.

As for all rubber seals, Steve Maney supplies them. See: http://www.stevemaney.com/products/oil seals.jpg

I've used both rubber as well as steel and never had a problem but I could see instances where you could get into trouble. There is a couple racing a side car in AHRMA that are going through the same sounding problem - it is a belt drive and oil is coming out from the crankshaft. It seems to have reoccurred after one or more oil seal replacements.

I would look at the condition of the crank sealing surface as well as the bore in the crank case for cracks, scratches or debris. Assuming the engine is in the frame, get up close with a hand lens as best as you can to inspect for scores, scratches, built up ridges on crank or debris. Try to establish as best as you can a known - ex seal surface good, check; seal bore good, check. It is a process of elimination. Without a tear down, you may not be able to do a thorough inspection of the seal bore and sealing surface. Also follow up on the recommendations provided above - mostly all good stuff.

B+Bogus · Nov 7, 2014

And I thought English was a common language... :roll:

I was just saying that my engine had the breather mods done so as to not pressurise the crankcase, and despite this it was still forcing oil out of the primary - including behind the clutch - until I changed the steel-jacketed seal for a rubberised one.

In plain English... the new seal fixed the leak.

To repeat Dances' observations, Steve Maney seems to think they're a good idea too, but perhaps we're in the minority...?

I know we're not all fans of a £7 fix, but I'm sticking with this one :wink:

Crank Oil Seal leak

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