Author Topic: Looking for help researching noise/vibration problem  (Read 20013 times)

Offline bmwcyclist

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Re: Looking for help researching noise/vibration problem
« Reply #50 on: March 22, 2020, 05:23:18 PM »
Test drive completed.

The TB work made a huge difference in responsiveness and overall performance.

Unfortunately, it made no change in the vibration and sound issue other than now the engine is quieter to it made the errant sound more clear.

You can hear the sound QUIT between 2 and 3 seconds into the video.

  • Batavia Oh
  • K75 1990, K75RT 1995

Offline Laitch

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Re: Looking for help researching noise/vibration problem
« Reply #51 on: March 22, 2020, 05:46:09 PM »
Good recording!

Now it sounds to me like vibration acting on a body panel or panel fitting. Are the airbox clips tight? Is the air snorkel loose. Is there movement of any fairing. Is a radiator cover grill loose?
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline bmwcyclist

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Re: Looking for help researching noise/vibration problem
« Reply #52 on: March 22, 2020, 07:11:28 PM »
Good recording!

Now it sounds to me like vibration acting on a body panel or panel fitting. Are the airbox clips tight? Is the air snorkel loose. Is there movement of any fairing. Is a radiator cover grill loose?

Thanks!

Airbox clips are in place in tight, I put in a new air filter during the TB work and also removed and reinstalled the air snorkel and front bottom of the faring.

The vibration is enough that I feel it and there is no significant wind/airflow to move a body panel.

  • Batavia Oh
  • K75 1990, K75RT 1995

Offline Laitch

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Re: Looking for help researching noise/vibration problem
« Reply #53 on: March 22, 2020, 07:24:19 PM »
The vibration is enough that I feel it and there is no significant wind/airflow to move a body panel.
I'm not referring to airflow; I'm referring to the sympathetic vibration of a part or fitting.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline bmwcyclist

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Re: Looking for help researching noise/vibration problem
« Reply #54 on: March 22, 2020, 07:31:23 PM »
I'm not referring to airflow; I'm referring to the sympathetic vibration of a part or fitting.

I thought so, just covering the bases.
  • Batavia Oh
  • K75 1990, K75RT 1995

Offline The Mighty Gryphon

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Re: Looking for help researching noise/vibration problem
« Reply #55 on: March 22, 2020, 07:40:24 PM »
At what rpm does the noise stop? 

My K75RT does a very similar thing.  The noise starts just above idle, somewhere between 1200-1300rpm and goes until the rpm gets to about 2000-2200.  Then it suddenly stops as yours does. 

The only difference with your noise is that it doesn't have quite the metallic clank to it that mine has, otherwise it's exactly the same.

  • In my garage in Marilla, NY
  • '91K100RS White/Blue
Current:
'91 K100RS16V "Moby Brick Too"

Past:
'94 K75RT "Ilsa, She Wolf of the SS"
'92 K100RS16V "Moby Brick" (RIP, deceased in a vehicular assault)
'94 K75S Special Edition Dakar Yellow "Cheetos"
'89 K100RS Special Edition "Special Ed"

Offline bmwcyclist

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Re: Looking for help researching noise/vibration problem
« Reply #56 on: March 22, 2020, 10:27:26 PM »
At what rpm does the noise stop? 

My K75RT does a very similar thing.  The noise starts just above idle, somewhere between 1200-1300rpm and goes until the rpm gets to about 2000-2200.  Then it suddenly stops as yours does. 

The only difference with your noise is that it doesn't have quite the metallic clank to it that mine has, otherwise it's exactly the same.

interesting. I will check.
  • Batavia Oh
  • K75 1990, K75RT 1995

Offline bmwcyclist

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Re: Looking for help researching noise/vibration problem
« Reply #57 on: April 05, 2020, 12:09:50 AM »
I believe I have found the problem.

As previously stated the sound / vibration seemed to be on the alternator side.

I spent some time with a mechanics stethoscope and the sound seem to be coming from the bell housing area.

I ordered a new alternator from enduralast, it arrived yesterday.

I pulled the alternator. I could find no play, although there seemed to be an almost imperceptible rough spot, the ne alternator did not have one.

I checked the alternator dog and found some slight play.

The monkey nuts were ok, but oddly worn considering I replaced them only a few months ago.

I removed the bolt holding the alternator dog and found it was only hand tight.

I put a lock washer under the bolt and reinstalled the dog. Now it has no play.

I installed the new alternator with a new set of monkey nuts.

Noise and vibration were gone, noticeable change in sound.

Went for a 5 mile test run, so far no return of noise.


.
  • Batavia Oh
  • K75 1990, K75RT 1995

Offline volador

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Re: Looking for help researching noise/vibration problem
« Reply #58 on: April 05, 2020, 12:33:47 AM »
I believe I have found the problem.
As previously stated the sound / vibration seemed to be on the alternator side.
I spent some time with a mechanics stethoscope and the sound seem to be coming from the bell housing area.
I ordered a new alternator from enduralast, it arrived yesterday.
I pulled the alternator. I could find no play, although there seemed to be an almost imperceptible rough spot, the ne alternator did not have one.
I checked the alternator dog and found some slight play.
The monkey nuts were ok, but oddly worn considering I replaced them only a few months ago.
I removed the bolt holding the alternator dog and found it was only hand tight.
I put a lock washer under the bolt and reinstalled the dog. Now it has no play.
I installed the new alternator with a new set of monkey nuts.
Noise and vibration were gone, noticeable change in sound.
Went for a 5 mile test run, so far no return of noise.

Great job! You've quickly become the resident alternator expert. Stay safe
  • NYC NY
  • 1991 K100RS 1993 K75S ABS
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Offline milq

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Re: Looking for help researching noise/vibration problem
« Reply #59 on: April 05, 2020, 02:00:00 AM »
Now we all know who to contact for alternator problems!
  • Southern IL
  • 1988 K75S

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