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Old 12-05-2009, 10:59 PM   #46
pommie john OP
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Quote:
Originally Posted by jackd
I wish you luck on your seal installation. So did you do the whole nine yards - form it in the bag, not touch the lip with human hands? I will also give it a run up with the transmission not installed - which should be interesting. Maybe the gods will smile on my mechanical skills again in regards to the GS - I'm due.
Yeah, did all that. One thing I noticed that may be relevant: I roughed up the ring first with 400 grit paper then 800. When i polished it by moving the paper around the circumference , the mark left by the seal dissappeared quite quickly, but then I rubbed it in a cross hatch pattern and the tell tale mark from the old seal re-appeared. I can only assume it was deeper than it looked.
I continued until I couldn't see it ar all.
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Old 12-21-2009, 04:57 PM   #47
Infracaninophile
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Ah Ha

Pommie:

Ah ha. I finally got it. The picture you posted (shown below) is with the seal already removed. I didn't understand that. Now that I'm getting ready to replace my rear seal, do you have detailed instructions? How do you remove that metal piece from the end of the crank? Does it just pull off?




I'm waiting right here to do mine right now on the parts. But not sure how to proceed:



Tom
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Old 12-21-2009, 05:16 PM   #48
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Quote:
Originally Posted by Infracaninophile
Pommie:

Ah ha. I finally got it. The picture you posted (shown below) is with the seal already removed. I didn't understand that. Now that I'm getting ready to replace my rear seal, do you have detailed instructions? How do you remove that metal piece from the end of the crank? Does it just pull off?


Tom
First: YOU MUST BLOCK THE CRANK TO STOP IT MOVING FORWARDS. If it moves by even a couple of millimetres, the thrust washer can fall off the rear main bearing and a major strip down will be needed.

Snowbum's site covers it all quite well, but a couple of extra pointers are:

I put a couple of bolts back in just nipped up, to hold the ring on the crank. I then used the ring as a fulcrum to lever out the old seal.

I then took the bolts out.

Then to get the ring off, I used an alloy drift to spin it on the crank until the bolt holes were about half lined up with the threads in the crank.
I made a slide hammer out of some 6mm threaded rod. I ground a hook into one end to grip the ring's bolt holes, and put a nut and washer on the other end and slid an adjustable spanner up and down against the nut and washer as a slide hammer while the hook was in the ring's bolt hole. I did this in diagonally opposite holes until ...eventually ...it came out.

The fitting of the new seal is covered earlier in this thread.
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Old 01-06-2010, 10:36 PM   #49
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I just got a copy of the BMW Service Letter outlining the correct installation process for the rear seal from a BMW parts supplier I deal with.

Just to confirm what was said earlier I quote from the bulletin: "you must pre-shape the seal prior to installation. The desired shape can be obtained by pushing the seal onto the drift (guide ring?) to install it. Make certain that the spiral formed on the seal lip is not damaged. This new seal will seat in rapidly if installed dry".

I had a bugger removing my guide ring during my previous attempt but someone here suggested that I use a drift and smack the guide ring rotationally at one of the flywheel bolt holes and work it off. It worked quite nicely for me.
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Old 01-06-2010, 11:33 PM   #50
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Quote:
Originally Posted by jackd

I had a bugger removing my guide ring during my previous attempt but someone here suggested that I use a drift and smack the guide ring rotationally at one of the flywheel bolt holes and work it off. It worked quite nicely for me.
Glad to be of service.

I'm off to Phillip Island in 2 weeks time. I'll let you know if it holds out.
I might start a whole thread on the race meeting.
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Old 01-07-2010, 07:56 AM   #51
Infracaninophile
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Pommie:

Just had mine done. When I mentioned to Matt about all of the various "methods" for installing the seal he just told me to watch. It was done in 10 minutes.

1. He used a drift punch to tap the seal guide just a bit and then just pulled it off with his hands.

2. He pulled the old seal out with a hooked seal puller. Not too gently either. It is sacrificed anyway.

3. He cleaned the area a bit to get any crud out and make sure it was dry.

4. He rubbed just a few drops of new motor oil on the seal for about 10 seconds. He said that's how Oak and Tom Cutter and others do it as well.

5. Pushed the seal into position with the seal install tool and pulled it into place with the flywheel bolts.

6. Checked the depth by eyeball to ensure we were fine.

7. Put the new o-ring on the inside of the seal guide.

8. Lightly heated the seal guide with a torch. Lightly and slowly.

9. Pushed the seal guide in place and just tapped the end lightly with a small hammer to ensure it was seated. Prior to heating it, it would not go in.

10. The end.


Now, whether or not it leaks is another matter. My engine isn't even in the bike so starting it w/o the trannie yet is not going to happen.

Tom
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Old 01-25-2010, 01:32 AM   #52
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OK folks. I just got back from Phillip Island where I retired from the meeting because the seal was leaking again!!!
I'm begining to think there is something else causing the seal to leak. Maybe excess crankcase pressure? Maybe the main beraings are worn and causing the crank to move about?
Any suggestions would be very welcome. The engine is due a total strip down now.

One thing that was suggested by a BMW mechanic who was there was that when nikasil cylinders get too hot, the rings do not seal properly and you get blowby and crankcase pressure.
I have recently fitted a full fairing and it runs a load hotter now, so I have decided to go back to the top half fairing. I'm not really sure if this could be a cause of the seal leaking. Any ideas anyone?

Thanks,
John
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Old 01-25-2010, 06:30 AM   #53
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First off you`re sure its the rear main and not the oil pump cover? Second, I replaced my seal a month or so ago and it leaked for the first 100 miles until it mated with the guide ring. I cleaned up what leaked out onto the top of the oil reservoir under the clutch housing and nothing new has appeared in the last few thousand miles, so I`m calling it good. Not sure how many miles you have on since you replaced yours, but it COULD just be a matter of the seal mating up to the guide ring. For your sake I hope it is.
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Old 01-25-2010, 07:47 AM   #54
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Pommie John - I feel your pain... Most of my rear seal issues started to appear just after I re-ringed the L/H cylinder. I'm going with the evidence that the bike was a bit of a smoker pre re-ringing and no longer suffers from that problem. I'm going to assume that my rings seated in quite nicely. On my first attempt at my seal replacement, my crankcase breather somehow glued itself shut (over the winter lay-up) and added to my woes. I always wonder about whether the seal has to 'bed in' - this might be the case for some, but the more I rode the bike, the more the leak showed. And yes I know all about the oil pump cover seal.
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Old 01-25-2010, 02:50 PM   #55
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Originally Posted by Airhead Wrangler
First off you`re sure its the rear main and not the oil pump cover? Second, I replaced my seal a month or so ago and it leaked for the first 100 miles until it mated with the guide ring. I cleaned up what leaked out onto the top of the oil reservoir under the clutch housing and nothing new has appeared in the last few thousand miles, so I`m calling it good. Not sure how many miles you have on since you replaced yours, but it COULD just be a matter of the seal mating up to the guide ring. For your sake I hope it is.
Well it seemed OK for the first couple of sessions, then a light mist of oil appeared on the shelf below the gearbox. I cleaned it off with brake cleaner to to monitor if it came back ( i was hoping it was a bedding-in thing) but it got progressively worse to the point where oil was coming out of the timing inspection hole ( I don't have a rubber plug in it). Oil was also visible at the engine/gearbox mating joint. It's definitely engine oil , it doesn't smell like gear oil.

The bike's on a truck coming back from the circuit and I'm away for work for a while so I won't be able to look at it for a few weeks.

I'll keep the updates coming though.

Thanks for the input everyone.
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Old 01-25-2010, 05:08 PM   #56
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So how many times have you actualy changed the seal? Twice? Mr. Mugwest once said that it took him three tries to get his to quit leaking and I'm not sure if he actually came to any conclusive reasons as to why his last attempt worked. Does the engine really need an overhaul? Come on! Go for another attempt - we're just getting good at this! I can pull the tranny and change the seal - step by step - from memmory.
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Old 02-14-2010, 12:29 AM   #57
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The bike has arrived back from Phillip Island and I've taken the gearbox off to see what's going on.

Well, I had a look in the back with a magnifying glass , and guess what...it's cracked!

It seems it wasn't the seal leaking at all, the crankcase is cracked from under the breather to somewhere down near the main bearing.

I'll post a couple of photos tomorrow.
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Old 02-14-2010, 08:56 AM   #58
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I asked the question of crank case cracks to Snowbum and he replied that it was something that was quite rare - he might have seen it once. Dying to see your photos.
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Old 02-14-2010, 09:15 AM   #59
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Well at least you know how to properly install rear main seals!
Robert
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Old 02-14-2010, 09:42 AM   #60
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Are you talking me or him? Don't hurt me now, I'm just getting up the guts to go back in there....
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