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Discussion Starter #1
2002 K1200 LT 52,385 Miles.

Existing crownwheel bearing shim thickness was 0.60mm
New bearing measured for 0.40mm suggesting that the original bearing was overshimmed by 0.20mm. This finding is consistent with previous data suggesting the excess preload is related to crownwheel bearing failure.

The bearing retainer was found to be broken on opening the drive. Cutting open the bearing reveals advanced pitting of both inner and outer races.





I pretty sure that this FD had been rebuild before. The crowngear assembly had been engraved with the number "5". This is not a BMW marking. I've engraved FDs that I have rebuilt in the past so I could identify the FD as one of my rebuilds if the FD ever came back to me. This is not my marking, I wonder if anyone recognizes it?

 

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Oh look, another failed bearing from excess preload.

What would be of interest is if you came up with something different. pitch the taper in favor of a roller, reduce the preload on the ball bearing, can it be done? Dunno.

What is the actual axial load on the ball bearing not "I believe it to be significant" which would lead to what is the minimum preload that one could use and still maintain proper taper bearing contact.

Experiment, even if it fails, it would be respected.
This, replace bearing, set to factory spec, repeat, yawn.
 

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New2rt said:
Oh look, another failed bearing from excess preload.

What would be of interest is if you came up with something different. pitch the taper in favor of a roller, reduce the preload on the ball bearing, can it be done?
Sure it can be done but then you would be listening to a lot of gear mesh noise and mesh wear.

New2rt said:
What is the actual axial load on the ball bearing not "I believe it to be significant" which would lead to what is the minimum preload that one could use and still maintain proper taper bearing contact.
I fiddled with trying to somehow quantify the preload of an assembled FD. I gave up. Trying to get an accurate preload thrust force measurement is essentially an impossible instrumentation problem because the force path is so short and indeterminate, while subject to thermal expansion effects.

I wonder who "5" is?
At least Curtis documents with clear closeup pictures! :wave [/QUOTE]
 

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New2rt said:
Oh look, another failed bearing from excess preload...., yawn.
If you find additional posts about final drives tedious, don't read 'em. Thanks.

I post these pics for the benefit of the rider who sent me the drive so they can see what happened inside their drive and for those others who might be interested. Many new folks are coming to the K1200LT having bought used bikes which are new to them. The intention of my posting in the public forum is to share the information that there is a known mode of failure and there does seem to be a predictable fix for this type of failure.

As far as discussing modifications to the BMW service manual specifications, or reengineering the drive with different bearings, that has been repeatedly hashed over many times. Suggesting experimentation outside the parameters established by the engineers who have designed the drive is beating the proverbial dead horse. It has been pretty well established that those drives that suffer this type of crownwheel bearing failure were assembled outside the specifications established by the design engineers and a properly set up drive won't suffer a premature failure.
 

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New2rt said:
Oh look, another failed bearing from excess preload.

What would be of interest is if you came up with something different. pitch the taper in favor of a roller, reduce the preload on the ball bearing, can it be done? Dunno.

What is the actual axial load on the ball bearing not "I believe it to be significant" which would lead to what is the minimum preload that one could use and still maintain proper taper bearing contact.

Experiment, even if it fails, it would be respected.
This, replace bearing, set to factory spec, repeat, yawn.
Let us know how your experiment progresses.
 

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I, for one, appreciate what Curtis has done, and continues to do. I found my bearing in virtually the same condition as the one just posted, then, using his video, repaired mine. My bike as 86,000 miles on it now, just returned from a 2,600 mile 4 day ride, and don't worry about my final drive any longer.
The only thing that sort of amazes me, I guess, is that some one will eventually post another thread asking what the probable cause of the final drive failures is.
Anyway, thanks Curtis. You made riding my bike a worry free event.

Frank
 

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fpmlt said:
I, for one, appreciate what Curtis has done, and continues to do.

Frank
Me too Frank. I read every post that has CharlieVT in it. Thanks Curtis....
 

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fpmlt said:
I, for one, appreciate what Curtis has done, and continues to do. I found my bearing in virtually the same condition as the one just posted, then, using his video, repaired mine. My bike as 86,000 miles on it now, just returned from a 2,600 mile 4 day ride, and don't worry about my final drive any longer.
The only thing that sort of amazes me, I guess, is that some one will eventually post another thread asking what the probable cause of the final drive failures is.
Anyway, thanks Curtis. You made riding my bike a worry free event.

Frank
But the point is, nothing has been done, it's just following the manual.

Experiment, throw caution to the wind, nothing to loose, and it's fun.

If we just follow we'd all be riding HD.
 

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New2rt said:
But the point is, nothing has been done, it's just following the manual.

Experiment, throw caution to the wind, nothing to loose, and it's fun.

If we just follow we'd all be riding HD.
HUH? This, replace bearing, set to factory spec, repeat, yawn.? I believe Curtis' point, and documentation, is that the failed bearings were NOT set to factory specs, even by the factory and/or BMW technicians. I don't believe that any rebuilt FD, set to factory specs, as prescribed Curtis, has ever failed.
So why experiment? What's to gain? If it ain't broke, don't fix it.

And I DO ride a Harley.
 

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fpmlt said:
HUH? This, replace bearing, set to factory spec, repeat, yawn.? I believe Curtis' point, and documentation, is that the failed bearings were NOT set to factory specs, even by the factory and/or BMW technicians. I don't believe that any rebuilt FD, set to factory specs, as prescribed Curtis, has ever failed.
So why experiment? What's to gain? If it ain't broke, don't fix it.

And I DO ride a Harley.
It's nothing new, ball bearings fail with excessive axial load. The cause is what it is, assembly, manufacturing, can't read.

If someone with basic mechanical skills never saw this site and followed the manual, he/she would have the same result. Curtis didn't prescribe the factory specs, he just follows them, nothing new.

If we didn't experiment we'd still be rubbing sticks together to start fires and riding old technology.

You ride a HD and that means?

I'll do you all a favor and let the FD conversations alone.
 

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Razmataz said:
Me too Frank. I read every post that has CharlieVT in it. Thanks Curtis....
+3...keep 'em coming, Curtis. I also appreciate you are documenting what is clearly an assembly failure on the part of BMW.
 

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To: Mr. New2rt.....What Curtis has continued to do for the benefit of the members of this site, has provided hope that an FD failure no longer has to be the dread of any LT rider....His research, conducted in his shed in the back of the house in little old Vermont, under less than clinical conditions with limited equipment, has pretty much proven to the minds of the fans here, that there is a way to deal with the questionable production standards involved in FD units of many LT's. His video alone is priceless to the few of us who probably can't afford to have the BMW dealer come and pick up their bike from 100 miles away, bring it to the dealership, and with carte blanche spend untold thousands to "just make it so"...Instead, we can with basic tools in our own garages and sheds at home and a minimum investment in parts, rebuild/repair our own FDs, and worst case, send them to him and have them rebuilt by a trusted technician for a small percentage of what the "stealer" would charge, and have way more confidence in the final result!
Now granted to casual visitors of this site, another re-hash of the FD failure/Crown wheel bearing failure may be "ho hum" to some, most of us (I think) really respect and appreciate that some random guy (Curtis) would take it upon himself to thoroughly investigate the reasons for the FD failures prevalent in our favorite motorcycle, and produce a video to help us repair our own drives, plus provide a service to our members without a shed or basic tools, of rebuilding our drives to factory specs for a reasonable cost.
I think that many people around the globe have a general respect for the engineering abilities of the Germans. However, through Curtis's efforts we have come to realize that if the product is not built to the engineering specifications, it will fail, but if you heed the engineering specs, it seems to last.
Being that we live in a free society, it is your right to express boredom with another investigative report from one of this sites favorite contributors. I would assume by now that you have gotten a more clear picture of our feelings about your expression of that bordom....And I am sure that we all wait with baited breath to hear the results of your experimentations on the redesign/re-engineering of the final drive assembly...
In other words...Stop screwing around denegrating a prize contributor to this site, and let us know when you have something constructive to add!!
 

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Here are some pic's on the three FD's I rebuilt today. The one on the left had 8000 miles on it since a dealer rebuilt it. It was 0.23mm over shimmed. Picture # 5 is the inner race. Pictures # 6 & 7 are from a 11,000 mile FD that had never been apart. The thinner of the two shims had slipped during the factory installation into the crown bearing.
 

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New2rt said:
But the point is, nothing has been done, it's just following the manual.

Experiment, throw caution to the wind, nothing to loose, and it's fun.

If we just follow we'd all be riding HD.
You seem like a person of much talk and little action.
 

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niel_petersen said:
Sure it can be done but then you would be listening to a lot of gear mesh noise and mesh wear.

I fiddled with trying to somehow quantify the preload of an assembled FD. I gave up. Trying to get an accurate preload thrust force measurement is essentially an impossible instrumentation problem because the force path is so short and indeterminate, while subject to thermal expansion effects.

I wonder who "5" is?
At least Curtis documents with clear closeup pictures! :wave
[/QUOTE]
I fixed the little emo for you..this is what you should have used..lol.




Curtis does a great job!
 

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New2rt said:
But the point is, nothing has been done, it's just following the manual.

Experiment, throw caution to the wind, nothing to loose, and it's fun.

If we just follow we'd all be riding HD.
I think he's done a bit more than follow the manual. It was his research and hard work that turned up all this. Well if you would of read all the posts you'd know You couldn't be more wrong newt.
 

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saddleman said:
Here are some pic's on the three FD's I rebuilt today. The one on the left had 8000 miles on it since a dealer rebuilt it. It was 0.23mm over shimmed. Picture # 5 is the inner race. Pictures # 6 & 7 are from a 11,000 mile FD that had never been apart. The thinner of the two shims had slipped during the factory installation into the crown bearing.

Dave and Curtis,

I for one have NO clue what the shim and over shimmed means, but I do appreciate the effort and skill and expertise of you two true mechanics and craftsman who make the final drive world a better place...

On a side note, DAMN Dave you eat a lot of party peanuts.. :) Is that what you get paid for those repairs?

Now I know what to get you if I ever do get the chance to swing by for a visit....
 

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saddleman said:
Here are some pic's on the three FD's I rebuilt today. The one on the left had 8000 miles on it since a dealer rebuilt it. It was 0.23mm over shimmed. Picture # 5 is the inner race. Pictures # 6 & 7 are from a 11,000 mile FD that had never been apart. The thinner of the two shims had slipped during the factory installation into the crown bearing.

Now this is interesting, pics 5 and 6.
How could that shim slip on the bearing and still fit in the cover? There would have been more resistance than one would expect and it would have been sheared. The shim OD is close to the bearing OD
I don't see anything that would have pressed it into the bearing to mold it in that shape.
Can't see anything that would have pressed it into the case oil relief either.
More pics of this and how it was orientated would be great.

As far as the other posts, yeah, whatever gets you through the day.
 
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