Crank seal, banging my head

acadian · Aug 12, 2015

Seal never leaked until recently, I'm on my third (rubberized) now and the problem seems to be getting worse. Oil scavenge rate is good, checked and cleared scavenge galleries, replaced oil pump gasket. It's not leaking from the primary bolts either. I've secured the seals with JB weld on the OD. Still no joy. No execessive blow by symptoms either. Some suspect a micro crack in the case itself.

Any thoughts?

seattle##gs · Aug 12, 2015

try a good engine breather like Krankvent

ashman · Aug 12, 2015

It is the thinest part of the motor, my orgianal case had a hairline cracks there from my younger days of flogging my motor from burnouts, we tried welding them up but so much oil coming out of the pours, ended up with another set of C/Cs, but it may not be your problem, have you tried going back to the metal band oil seal ?

Ashley

acadian · Aug 12, 2015

ashman said:
It is the thinest part of the motor, my orgianal case had a hairline cracks there from my younger days of flogging my motor from burnouts, we tried welding them up but so much oil coming out of the pours, ended up with another set of C/Cs, but it may not be your problem, have you tried going back to the metal band oil seal ?

Ashley

I've tried locating the tin seals but nobody seems to carry them anymore. That's what i had in there originally, before the belt install

1up3down · Aug 12, 2015

acadian, I am having the same problem

Installed a new main seal a while back it leaking engine oil into me dry belt primary, not a lot but it is annoying

just ordered and received a new seal and this time I am use some oiled up electrical tape and put it lengthwise on the crankshaft before slipping the new seal in place over it, trying to avoid even the slightest seal tear on its journey into place

I spoke with Norvil and they recommended they sell me the rubberized seal stating that in their opinion it sealed better

they did not say anything about using an adhesive to secure it in place but Jim Comnuz here says to use some Yamabond, I will try that this time

just some thoughts

pete.v · Aug 12, 2015

acadian said:
I've tried locating the tin seals but nobody seems to carry them anymore. That's what i had in there originally, before the belt install

Ok, new belt drive. I would like to ask how much oil are you talking about.

The reason I ask is when I remove my outer Primary cover, I usually have some oil on the inside bottom and is simply wiped off with a rag and on we go. Are you saying you have a measurable amount or are you looking for perfectly dry results. I am sure there are many dry units but I am also sure there are some not so dry with belt drives. That being said, I also think that it is just fine that I have a drip or 5 under the bike after a good run.

I find a little bit of oil in primary is acceptable, particularly when I aften go 80 to 90mph for extended times. I have two reed breathers, one off the timing side and one off the original lower left location. Both functional and effective, yet, it's a hard running hot streeter and the perfection is in the ride. I think my bike is as dry as it can be under the circumstances.

acadian · Aug 12, 2015

pete.v said:
acadian said:

I've tried locating the tin seals but nobody seems to carry them anymore. That's what i had in there originally, before the belt install

Click to expand...

Ok, new belt drive. I would like to ask how much oil are you talking about.

The reason I ask is when I remove my outer Primary cover, I usually have some oil on the inside bottom and is simply wiped off with a rag and on we go. Are you saying you have a measurable amount or are you looking for perfectly dry results. I am sure there are many dry units but I am also sure there are some not so dry with belt drives. That being said, I also think that it is just fine that I have a drip or 5 under the bike after a good run.

I find a little bit of oil in primary is acceptable, particularly when I aften go 80 to 90mph for extended times. I have two reed breathers, one off the timing side and one off the original lower left location. Both functional and effective, yet, it's a hard running hot streeter and the perfection is in the ride. I think my bike is as dry as it can be under the circumstances.

It's a steady drip drip drip, probably 1 - 2 ounces.

pete.v · Aug 12, 2015

acadian said:
It's a steady drip drip drip, probably 1 - 2 ounces.

Yea, that's a bit much. I think that would be a bit too much for seal blow by also, particularly when you say your scavenge is working well.

acadian · Aug 13, 2015

Alright, have the inner primary cover off. The oil is certainly coming from somewhere behind the inner cover, the seal is dry, as are the bolt holes. Oil is present between the crank/inner primary mating surfaces. Tracing above, I cant find anything except a small trail of oil residue from the rear crank case stud/nut just below the barrel. If I do have a hairline line crack in the case behind the inner primary, where is it most likely to develop?

ashman · Aug 13, 2015

Are you sure its not the 3 mounting bolts that are leaking as that is a comon area, did the bolts have any sealant put on the threads, my cases where cracked around the oil seal area, like I say the thinest part of the C/C, if its not coming out of the seal then I be pulling the inner case off and checking the mounting bolts, just because you can't see any oil from the bolts don't mean they aren't leaking from there.

Ashley

pete.v · Aug 13, 2015

ashman said:
Are you sure its not the 3 mounting bolts that are leaking as that is a comon area, did the bolts have any sealant put on the threads, my cases where cracked around the oil seal area, like I say the thinest part of the C/C, if its not coming out of the seal then I be pulling the inner case off and checking the mounting bolts, just because you can't see any oil from the bolts don't mean they aren't leaking from there.

Ashley

Usually the lower right(4:00 am)....

1up3down · Aug 13, 2015

what is the recommended sealant to put on the three bolts that hold the inner cover to the crankcase?

Onder · Aug 13, 2015

I used locktite blue but silicone would do fine. Just make sure both the bolts and the holes are chemically clean first.
Same problem as you, used the rubber seal, used tape on the surface well oiled and
with great care installed. Took three seals to finally get 99.5% oil free.
Also have Jim's sump installed breather. Not cheap but effective.

JimC · Aug 13, 2015

If you don't relieve the crankcase of pressure you are going to have oil pass the crankshaft seal and other places, regardless which oil seal you try. Many posts on this forum about this problem and solution.

acadian · Aug 13, 2015

JimC said:
If you don't relieve the crankcase of pressure you are going to have oil pass the crankshaft seal and other places, regardless which oil seal you try. Many posts on this forum about this problem and solution.

Running a reed valve in the crank vent.

The bolt holes are dry, I know this because I sealed it up with permatex around the holes, and thread sealant on the bolts. When I took the inner primary off, the oil was evenly blotted around the entire crank mating surface... except around the bolts which were dry.

Chris · Aug 14, 2015

Hi

A few years ago my race bike had the same problem I changed seals 3 times. When we stripped the engine the cases looked fine, no cracks hairline or otherwise. We had the cases sealed with a pressure coating by a firm in Slough. They also did my early Maney barrels that leaked. Problem solved.
I dont know if it was heating up the cases to put in the new bearings that brought it to a head. I know from friends that Atlas & other cases could be pourous but Commandos dont seem to have this problem. Then again they are now 40 year old cases

I think the factory used to paint them.

Chris

Keith1069 · Aug 14, 2015

Even with a breather valve (Norvil (Marine)one way hunk of brass) I get some oil in the primary. Now on a rubber seal superglued in place. Last seals were metal housed and often had the tiniest nick on the lip. They could hardly be felt but visible under a 3 x glass. After some sumping and probably too many revs at startup it would leak. At least that was my usual theory. After 1750 miles there is a 1/4 teaspoon in the lower front case and a tiny pool in the clutch adjuster plug recess! Why there? The timing and chain plugs are dry. I also have a belt and of course the 3 inner case fixings are sealed.
If you don't leave the bike a week and don't have a sump full of oil and don't rev it on start up then its probably not a reason for yours to leak.

edgefinder · Aug 14, 2015

I've helped find oil leaks on friends vintage race bikes by cleaning the motor and let it dry completely, dust everything with baby powder, start motor. The leak will appear very obviously. I would do the same with your bike with the primary cover off.

Crank seal, banging my head

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