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Old 11-25-2009, 06:52 PM   #16
pommie john OP
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Quote:
Originally Posted by RecycledRS
What are you doing to try and reduce the crankcase pressure? It could be that with the revs your turning racing the case pressure is biuilding too high and dumping out the rear seal.

Nothing much has changed over the years, so I can't really see that being the problem. At the last race meeting it was a very low speed circuit and I never got to full rpm, and it leaked there.

I have a deep sump and longer oil pick up. This means I run the normal amount of oil, but it sits lower from the engine increasing the crankcase volume by a litre or so, and I have the later reed valve breather.

I have just put a full fairing on it so it's getting a bit hotter. Maybe that could be an issue?
The oil temp was 114C which isn't too bad.
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Old 11-25-2009, 09:00 PM   #17
jackd
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This thread is ringing home to me. I will soon be into my third rear seal change in as many years. I actually suspect that this is the fourth seal in the bikes life. My attempt at re-surfacing the crank shaft guide ring is what I suspect as being the cause of my latest leak. The plan is to buy a new guide ring. When I pulled the clutch housing last time, there was no clear indication of what was the cause except for some dampness around the inner seal lip area. The pump cover o-ring, as well as the guide ring o-ring were also replaced. The knowledge that others have also had multiple seal changes gives me hope that the guide ring might be the cause. But I might start looking for cracks in the housing (Bike has only 46k on it) Running it withough the transmission might be a thought as well. Anyone else ever tried re-surfacing their guide ring and had bad results?
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Old 11-25-2009, 09:14 PM   #18
Wirespokes
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There are other things that can cause leaks back there. One of them is the ORing at the guide ring. It fits between the crank and guide ring. I don't know why that one is so important, but it is. I chased a leak several times before finally replacing that sucker just because I'd done everything else, and it went away.

If your crank bearings are worn it can cause excessive rocking at the crank/seal connection and allow a leak.

I also remember when the new style seals first came out, some guys had problems getting them to work, and there were all sorts of different ways to prep and install them.
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Old 11-25-2009, 09:27 PM   #19
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So what are these ways of prepping these new seals? I put mine in dry as has been the suggestion in this forum. Others do different. I install many seals in my trade and I have never seen a fussier set-up than this. Rank novices are having better luck than an old salt like me!
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Old 11-26-2009, 07:27 AM   #20
Wirespokes
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I don't recall the variations I'd heard back then. I think the accepted method now is to soak them in oil for several hours stretched over a comparable surface like the guide ring. Check 'the bum' for his take on it.

As I recall, the guide ring is highly polished. How did you re-surface it? It just may be it needs replaced, and those dumb things aren't cheap (as if anything on these bikes is!).
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Old 11-26-2009, 11:59 AM   #21
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Might be the oil pump o ring. Worth replacing (Here we go.) "while you're in there."
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Old 11-26-2009, 08:26 PM   #22
jackd
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I made an arbour for the guide ring and spun it in my drill press. The finish was of a polished nature. The 'ridge' from the previous seals wasn't terribly bad and I would guess that I might have lost around .002" - .003" from the total diameter when all was said and done. Others have stated that they had performed such an operation and had success. A new guide ring won't kill me cost wise and I will go this route. I'm curious about this cracking that people found in their cases. Anyone ever find any leaks from the plugs that blank off the galleries for the oil feel to the top end?
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Old 11-29-2009, 07:54 AM   #23
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Well, I checked with the 'Bum' on this one. Very down to business individual who gets to the heart of the matter. He personally puts his seals in warm oil and shapes them beforehand - actually prefers having a warm engine block. He says that either dry or wet going in will work. He personally has never seen or heard of casting flaws in that area, but he has seen damage caused by people not blocking the crank and torquing the flywheel bolts - I make a point of always blocking mine. He says that you can run the engine with the transmission removed to hunt the actual leak source - recommends talc powder if the leak is hard to find and even a red dye in the oil if you are really unsure of the source. He also states that the guide ring finish should be very smooth, so the inner seal lip runs on a perfect surface.

So I am now on the hunt for the BMW tech bulletin which covers the rear main seal installation. I've always put my seal in dry - because of the teflon lip. Anyone have a source for this bulletin?
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Old 11-29-2009, 07:50 PM   #24
bmwrench
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I can't lay my hands on the bulletin, but both Robert (Wirewerker) and I remember that BMW told us to install it dry, and that it would "seat more quickly" that way. Since then, some service school instructors have suggested the seal be placed on the seal journal several hours before it is installed, something I have never done. I have always wet the O.D. with WD-40 to install it, using the aftermarket seal installer. I have yet to have one of them leak when using this technique. (knocking wood). A light wetting of the seal surface with WD should do no harm, but I have not done that, either.

This seal has two great advantages, as far as I'm concerned: Since it is teflon, it should not be affected by oils or time, and it's lack of a garter spring prevents wear on the seal journal.
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Old 11-29-2009, 11:04 PM   #25
jackd
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Dry for the teflon seal does make sense to me - to aid seating possibly. Preforming the teflon inner lip - very carefully - also makes sense. I was hoping that the seal that I put in this summer would bed in with use but it hasn't been the case. I had mirror polished my guide ring before I installed it. I'm going to spring for a new guide ring this time and give it a go. I can only take heart that Mugwest stated that it took him three tries one time to fix his rear seal and he still wasn't sure what he did that worked in the end.

As a side note, in my field of aviation maintenance, I used to assembly large propellors from a certain U.S. manufacturer. Wonderful bits of engineering. However up here in our harsh Canadian winters, the large o-ring seals that lived inside these things used to bypass oil. It was discovered that a certain very large individual at the factory was stretching the shit out of these seals to get them onto their sealing area. The indentations from his fingers which he created when he pulled like a bastard were deforming the seals - but would only show up during our -30 degree temperatures. Normal operating temperatures would not cause the seals to leak. So folks, I treat my seals with great care when I install them.
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Old 11-29-2009, 11:28 PM   #26
bgoodsoil
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jackd, can you tell if it's leaking from inside sealing surface or the outside? A leak's a leak but I'm curious as to which gave up the ghost first.

How bad is it leaking?
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Old 11-29-2009, 11:37 PM   #27
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About 2 tablespoons are laying under it after a good two hour ride and my clutch is getting fouled. A real irritant. I seated in the outer perimiter of the seal with a product similar to Yamabond - so that is not the leak source. I have to say that it must come from the inner lip because it's slinging outward - but I can honestly say that looking at the rear housing area, nothing looks to be the definitive source. I might try 'dye penetrant developing solution' - we have it at work and use it on oil leaks when we aren't quite sure. Mr. Snowbum suggested that I throw a dye in the oil and run it to find the exact source of the leak. He says that the oil feed galleries for the top end have been known to weep but never have been a major source of leakage in the rear case area - even though they carry oil at 75 psi and high volume.
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Old 11-30-2009, 02:19 AM   #28
pommie john OP
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Quote:
Originally Posted by jackd
I was hoping that the seal that I put in this summer would bed in with use but it hasn't been the case. I had mirror polished my guide ring before I installed it.
I spoke to my engine tuner in England who told me not to mirror polish the ring. he said use 800 grit emery in a cross hatch pattern like honing a bore. that is supposed to make it bed in nicely.

I have fitted my seal and should have time to run it up next weekend.
i'll let you know how it goes.
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Old 11-30-2009, 07:31 AM   #29
jackd
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So an Australian guy talks to his fitter in England for tech support? I'll have to believe what he says because I'm from the Commonwealth too!

Seriously, thanks for that titbit of info about finishes. I don't want to play around with my guide ring anymore and take more material off of it - a new one it will be. I wish you better luck than I have had on this one. I just posted a query on GSpost about rear seal installations and as per the 1150 manual, it says to put the seal in wet. Ask your tech what he thinks about this.
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Old 11-30-2009, 08:41 AM   #30
bpeckm
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Are you positive it is the seal, and not the oil-pump o-ring?

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