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Old 01-04-2015, 08:29 AM   #1
anderstornvig OP
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Broken ring and filler plug in rear bevel drive housing

Hi all,

I started taking my '85 R80G/S apart this weekend. I might regret it later this spring when everyone else is outthere(!), but I'm curious about how it works and I want to check the condition of as much as possible, replace if necessary.

One thing I knew was not in a good condition was the rear bevel drive housing (I think it's called). Oil is leaking from the driveshaft filler plug because the thread is gone, so I have to cut a new thread. That was the obvious problem. When I opened it, I saw this.



You're looking into the front of the rear bevel drive housing. The broken thingy should be part no. 4 here.



Is this fix as easy as it looks? Replace part no. 4 and bolt it all back on. My Haynes manual says it's difficult to disassemble the housing but not why. Would you replace all the small parts while you're at it?

Any advice appreciated!

The bike has run about 110 Mm but the speedo is about +20 off, the odo shows more than it should.

anderstornvig screwed with this post 01-04-2015 at 08:58 AM Reason: Smaller images
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Old 01-04-2015, 08:50 AM   #2
Pokie
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This is why it's important to remove the seal lock ring when doing a thread repair on the filler or drain plugs of the drive shaft.

The difficulty in replacing the lock ring is #1- making or buying the proper tool, #2-making or buying the tool to remove the pinion, #3-the case needs to be heated to remove (unscrew) the lock ring and having a torque wrench to re-torque the pinion nut when done. In actual reality, the damage you are seeing is pretty minor. The damage will in no way affect the lock rings function (as long as it's tight). I would probably grind the end of the filler or drain plug so it is NOT contacting the lock ring and call it good. Replacing the lock ring doesn't require any re-shimming but can open a can of worms.
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Old 01-04-2015, 09:15 AM   #3
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Quote:
Originally Posted by anderstornvig
Oil is leaking from the driveshaft filler plug because the thread is gone, so I have to cut a new thread.
+1 what Pokie said.
If the filler plug threads are indeed gone then now is the time to fix them.
http://www.advrider.com/forums/showthread.php?t=1028991

If it leaks mostly because that the wrong filler plug bolt (bottoming before sealing two stacked crush-washers) then buy the correct bolt and ride-on.

The fix needn't be expensive. Find someone in your area with the correct special tools.

The pinion nut looks like it's backed-off a bit. Is it torqued down fully?
Torque on that nut should be 165 Nm (122 ft/lbs). Sometimes they're found to be finger-tight, which is somewhat alarming.
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Renner screwed with this post 01-04-2015 at 09:28 AM
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Old 01-04-2015, 10:01 AM   #4
disston
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I think you should take it apart because you still have to fix the leaking threads of the driveshaft. The proper fix of these threads is to take the pinion and the threaded ring out so the filler plug can be Heli Coiled. Do it as described by Pokie.
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Old 01-04-2015, 10:31 AM   #5
anderstornvig OP
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Hi, thanks for the quick answers..!

The thread is actually gone, it's almost flat inthere, so my plan is to cut a new one, slightly bigger than standard of course, buy a new plug and grind it to the proper length if necessary, as you also suggest.

I wasn't aware that the plug was wrong before I opened and took the picture above. The previous owner must have put it there and sold the bike to me : ). At least it seems like that wrong plug have caused both the lock ring and the thread problem after tightening it too hard.

Will check the torque of the pinion nut, thanks!

Replacing the lock ring or not. I'm glad to hear it doesn't look that serious. It looks like the black end of the driveshaft touches, or almost touches the lock ring when assemblied. I could fear that the dent in the lock ring makes it touch the black when it shouldn't.

Perhaps related, I'm also wondering why the ring has four holes. In my picture they point to each corner. Can someone explain why it looks like this? Just to let oil in?
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Old 01-04-2015, 10:40 AM   #6
Renner
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Quote:
Originally Posted by anderstornvig
Perhaps related, I'm also wondering why the ring has four holes. In my picture they point to each corner. Can someone explain why it looks like this? Just to let oil in?
four holes or castellations to receive the special tool, ref. pics in the link above.

Also a good idea to use some variety of thread inset to return the threads to the original size, for the next owner.
look into Time-sert and others.

Is there a shop in your area that's familiar with the old beemers?
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Old 01-04-2015, 11:03 AM   #7
disston
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I have heard of somebody patching this thread the way you have planned. I think a proper Heli Coil or Timesert is better.

The PO may not of known the damage or problem. Many substandard parts around. They even sometimes come from dealers.
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Old 01-05-2015, 06:57 AM   #8
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If you can find one the correct length, I would use a time-sert for repair.


Mike
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The good thing is, your damn motor can't read. If it says oil on the container, it's pretty much OK to dump in there.... ED.
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Old 01-05-2015, 07:38 AM   #9
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You could also ship it to Ted Porter at the Beemershop and have him install a timesert (maybe even have the drain plug done as well?). Ted's got all the removal tools and a custom made tap guide to cut the new threads straight (not easy to do). He'll install a new threaded ring, input seal and fill plug. Probably not much more expensive once you factor in acquiring all the tools you'll need.

I made the mistake of having a local "tech" attempt to do this on both fill and drain plugs and he didn't have the proper tools and really fouled it up to the point that it could not be corrected (Ouch!).
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Old 01-05-2015, 11:04 AM   #10
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There may be someone closer to Denmark with the right tools. :)

Here in the US, there are quite a few shops with the jigs to drill/tap straight for the helicoil. I'm just one of them.
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Old 01-05-2015, 11:12 AM   #11
disston
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BTW, I don't think anybody mentioned yet the gear oil visible in the first pic. It is latte colored, or in other words, it has water in it. The gear oil in the transmission and the final drive should be looked at. If not black/brown looking but show any amount of contamination with water change it. This is another common problem and needs to be attended to. If after one change it shows still the latte color change it again. Usually 2 is enough but the final drive can be harder to get clear.

Now you have to keep an eye on it. The most common place for water to get into the transmission is the speedo cable boot on the rear of the trans where the battery ground cable is. New rubber boot is often called for.

Maybe the water is only in the drive shaft? Bad threads would cause this. But check all three, trans, FD and DS.
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Old 01-05-2015, 01:29 PM   #12
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Quote:
Originally Posted by AntonLargiader View Post
There may be someone closer to Denmark with the right tools. :)

Here in the US, there are quite a few shops with the jigs to drill/tap straight for the helicoil. I'm just one of them.
Good point! Didn't notice his location. Hey, my grandparents were from Denmark!
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Old 01-05-2015, 02:04 PM   #13
anderstornvig OP
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Quote:
Originally Posted by Renner View Post
http://www.advrider.com/forums/showthread.php?t=1028991
Excellent images at the end of that thread. It's much clearer to me how it works now.

Quote:
Originally Posted by AntonLargiader View Post
There may be someone closer to Denmark with the right tools. :)

Here in the US, there are quite a few shops with the jigs to drill/tap straight for the helicoil. I'm just one of them.
Quote:
Originally Posted by ccmickelson View Post
Good point! Didn't notice his location. Hey, my grandparents were from Denmark!
Yay! Can they fix my bike? : )
I don't know of anyone in Denmark who work with the boxers specifically. Service maybe but not the "hard" stuff. Luckily, Denmark is close to many other countries, if I get in over my head.

Quote:
Originally Posted by Renner View Post
The pinion nut looks like it's backed-off a bit. Is it torqued down fully?
Torque on that nut should be 165 Nm (122 ft/lbs). Sometimes they're found to be finger-tight, which is somewhat alarming.
Quote:
Originally Posted by disston View Post
BTW, I don't think anybody mentioned yet the gear oil visible in the first pic. It is latte colored, or in other words, it has water in it. (...) Maybe the water is only in the drive shaft? Bad threads would cause this. But check all three, trans, FD and DS.
Well-spotted, very helpful. There's latte in both the FD and the DS. Have changed it twice without proper cleaning in between (was on a trip). Gear oil looks fine.

Unfortunately I can't check this right now. But if the pinion nut is actually backed-off a bit (which it is compared to the images in the link above), can watery oil then get from the DS to the FD? In that case, with a little luck, the only leaks are at the filler plug and the pinion nut. What do you think?

The speedo doesn't work anyway, so I will go over that and possible leaks around it as soon as possible.
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Old 01-05-2015, 04:40 PM   #14
ccmickelson
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Quote:
Originally Posted by anderstornvig View Post
Yay! Can they fix my bike? : )
I don't know of anyone in Denmark who work with the boxers specifically. Service maybe but not the "hard" stuff. Luckily, Denmark is close to many other countries, if I get in over my head.
You might check with S Meyer in Germany http://www.meyer-bikes.de/.
I have sourced quite a few hard to find parts from him. He might do that kind of repair or recommend a good tech in your area.
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Old 01-05-2015, 05:01 PM   #15
disston
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There are three major parts of the bike all in a row that all use gear oil. The transmission, the drive shaft and then the final drive. There are seals in between each of these units but the seals go bad and oil can transfer from one place to the other. So it is a part of normal maintenance to check the oil levels. If the oil is high in the final drive it may be low in the drive shaft. If latte colored oil is found in any unit they need to all be checked. Seals may need replacing.

I think with latte in the FD and DS the water is getting in at the fill plug of the DS and migrating to the FD. That ring that is broken by the fill plug also has the seal between the DS and FD. It is suspect big time right now.

Water can also get in the FD from it's fill plug and the breather on the top of the unit (I had to replace that unit once, tiny little hole and the FD would fill with water in no time.) May be other place water can get in.

It is really strange in a way that so much water seems to be able to get in but not all the oil leaks out.

Good news about no latte in the trans.
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