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Discussion Starter #1
I have about 270k miles on LTs and have encountered just about every problem imaginable but I have a new mystery to solve.

While riding on a old, rough two lane road I heard an intermittent banging sound coming from somewhere around the engine area. There was no place to pull over so I continued to ride at a slow speed for about a mile during which time the sound continued.

With the bike on the center stand I confirmed there were no obvious loose parts and started the engine with no unusual engine noise. Then I put it into gear. When I began to rev the engine the noise started and recurred with varying frequency and intensity until I took it out of gear. I would describe the sound as similar to a 14mm nut ricocheting around inside a fairly strong metal contained area.

Fearful that it was something loose in the transmission or final drive I called a tow truck to take the bike to San Jose BMW. So far they haven't been able to reproduce the noise. They drained the final drive and transmission and found no signs of metal in the fluids. They removed the swingarm to examine the drive shaft and found nothing unusual. They road tested the bike about 100 miles last weekend and no noise.

What could this have been that it can't be reproduced? Has anyone here ever heard of such symptoms not associated with tranny, or FD?

Any help is appreciated.

Cheers!
 

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Wrencher Extraordinaire
2005 K1200LT
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Wow that is a good one Bob. The only difference between in gear/clutch out and not in gear/clutch out is a second shaft is now turning in addition to all the other "bits" that normally turn. I have no clue where to go next on this. I am sure that if it comes back and you ignore it it will finally reveal itself.
 

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I wuz gonna suggest a look at the torque settings on the exhaust header bolts - then I read where SJBMW rode it for a 100 miles and didn't hear it, so there went that suggestion. :(
 

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ltcommuter said:
While riding on a old, rough two lane road I heard an intermittent banging sound coming from somewhere around the engine area.

Then I put it into gear. When I began to rev the engine the noise started and recurred with varying frequency and intensity until I took it out of gear. I would describe the sound as similar to a 14mm nut ricocheting around inside a fairly strong metal contained area.
I haven't thought this through yet, but I'm wondering whether the rough road caused some bit of the reversing drive train to shift from its rest position to interfere with a gear on a tranny shaft. At any point in the diagnosis, did you find the reverser knob slightly out of position?
 

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Discussion Starter #5
mneblett said:
At any point in the diagnosis, did you find the reverser knob slightly out of position?
Not yet, but it will be the first thing I check when I get to SJBMW tomorrow!
 

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Old Slow Guy in A Fast Car
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Sounds like a Loose Nut behind the handle bars to me. :histerica

Sorry but someone had to say it. :D
 

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katnapinn said:
Sounds like a Loose Nut behind the handle bars to me. :histerica
That's a lot better than what I had. I had, "Sounds like a short between the foot rests and the handlebars." :D

Hope you get it sorted out, Bob.
 

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I only have experience with this from the perspective of my 1100RT. I never tried it on my 2000 LT.

Shortly after buying my 99 RT last year I thought I'd felt an odd vibration/bumping in the rear end. Once home, I put it up on the center stand and started the engine and put it into 1st gear. Man, what a racket and bouncing around it made. Like a universal joint on a car/truck going out. I also did the 9 o'clock/3 o'clock and 6/12 wiggle test on the rear wheel (with the engine off, of course :rolleyes: ) I felt a little movement with the 3/9 position. So I figured I'd better pull the driveshaft and check the u joints and seals.

The drive shaft and joints were in great shape. No binding, no corrosion. I lubed the spines and put it back in. I did find the needle rear drive pivot bearing was beginning to come apart. Put the replacement bushing from Rubber Chicken Racing in and all was good again. Still is.

But what caused the shaking and jumping around while in gear on the center stand? A couple of days later I read a post on the BMWST forum that explained that the extreme angles the driveshaft encounters when on the center stand with no weight on the rear causes the jumping around. Don't do it. Service department at BMW Motorcycles, Grand Rapids, MI, confirmed that.

PERHAPS, that is what you're encountering with your LT. It may not be the drive shaft but may be something else. (How's that for being conclusive!) I would think the final drive pivot bearing would be getting a lot of movement on a rough road. YMMV
 

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Maybe I can help. Have you checked the drive shaft yet? A while back at about 120k on mine every time I hit a bump I would hear a "knock". very hard to hear where it was from. Pulled the FD and found the rear half of the U joint with no bearings, so it was bouncing around. I have post of pics if you want to see. Changed it out and no noise. Just a thought. Hope this helps.

Zeke
 

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By the way. Love the Avatar. IF ONLY THEY WOULD.
 

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You may consider checking the splines on the forward u-joint of the drive shaft. If the driveshaft is not installed over the snap ring it will slide to the rear and at this point it will wallor the splines enough to offset the coupler and then get into the inside of the swingarm thus sounding like a little man with a big hammer wanting out.
 

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Discussion Starter #12
Thanks for all the interesting ideas guys! SJBMW completely removed the swingarm and drive shaft and found nothing unusual except a slightly crushed bearing which they replaced.

Zeke - In Europe they would be run off the road for not staying to the right!

Mark - The reverse handle was in the proper position.

Matt - The 1100RT and LT must have different drive line angles since the prescribed method to determine early final drive failure is to put the LT on the center stand, get the rear wheel spinnning fast in 4th or 5th gear then pull the clutch, cut the motor and listen. I've done this several times and don't hear any noises from the drive shaft. Unfortunately, I have heard noises in the FD! :(

The "nut" or "short" between the handlebars and the footpegs should definately be considered the problem. It's all a figment of my imagination.

I just rode the bike home and no noise or incidents... yet.

Cheers!
 
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