Eish.....What to do .....what to do ...The second chapter

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Coxwain

Race Dog
Joined
Nov 7, 2009
Messages
4,164
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Bike
BMW R1150GS
https://wilddog.net.za/forum/index.php?topic=213716.60

I left  off the last post with "a gear box problem"....which for me is not too serious as it can be fixed fairly quickly without too much expense.
So I whip off the gear box, open it up and what do I find ................................nothing ....nada .....no problems , if fact it looks perfect , with clean oil and obviously well maintained.
Now I'm properly pissed off , cause this is the second time I have striped a box to find nothing wrong with it , and I haven't discovered the source of the knock. Im pretty worried by now, as I can see some major expense in my immediate future.
So in a blind panic I rush of to the great Orical in the cloud.....GOOGLE !!!! and start a frantic search.
I found this  :eek: :eek: :eek: 

I've owned by bike for about 10 weeks now but an issue has cropped up that is concerning me a little. I thought I was getting used to all of the odd noises this bike makes but this one has only cropped up more recently. When the bike is at operating temp (5 bars) and I'm at a stop light with the clutch lever pulled in and "in gear" there is a very noticeable "deep knocking" noise coming from the centre of the engine. The noise goes away most of the time when I shift into neutral and release the lever but sometimes it's there even in neutral but to a much lesser degree and always goes away if I pump the clutch lever a couple of times. It's so bad I'm now in the habit of shifting into neutral at every stop light so I don't have to sit there with the knocking noise in my engine and counting the worry beads.


And the problem is .......

This engine had been knocking only when hot with the clutch lever pulled in ever since I purchased it at around 30,000 miles. It turned out to be what I had long suspected, crankshaft end float. I could even re-create the knocking sound by grabbing the clutch and forcing the crankshaft backwards and forwards by hand. I suspect the aluminium shell bearing failed because of overheating and or lack of lubrication at some point.

I have since learned that BMW changed/superseded this particular bearing, perhaps to help cope with excessive heat.

The faulty main bearing may have contributed to the early failure of the main shaft gearbox bearing, the one nearest the crank via excess radial movement of the crank. I have wondered if excess radial movement could have place extra load upon the gearbox bearing that failed prematurely, the one closest to the crank. It's up for debate.

I also burned out five starter motors in the last 34,000 miles. I put this down to the engine becoming harder to turn over as the bearing slowly degenerated . The replacement engine sounds completely different when I hit the start button
 
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