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#996349 - 09/07/17 11:56 PM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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MontanaBud Offline
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This may be nothing out of the ordinary, but I did just put the bike on the center stand, started the engine, and put it in 1st and slowly let out the clutch. I heard a clatter in the lower end of the swing arm. The clatter disappeared when I twisted the throttle slightly.

Anything telling here?

#996361 - 09/08/17 12:34 AM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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TheOtherLee Offline
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Wilsonville, Oregon, USA
Bud -
Drained into a CLEAN pan, oil can show glitter, feel gritty. Chemical analysis can show wear in specific materials - see here for example. Blackstone Labs will give a good laymans interpretation of the results - so you don't have to be a chemical engineer to understand them.

Magnetic drain plugs can be helpful. Beemer Boneyard has 'em.

Last edited by TheOtherLee; 09/08/17 12:46 AM.

Channeling farfegnugen since 2011.
#996362 - 09/08/17 12:46 AM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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dirtrider Offline
The Oracle
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Originally Posted By: MontanaBud
This may be nothing out of the ordinary, but I did just put the bike on the center stand, started the engine, and put it in 1st and slowly let out the clutch. I heard a clatter in the lower end of the swing arm. The clatter disappeared when I twisted the throttle slightly.

Anything telling here?



Evening MontanaBud

Normal, basically just a stack up of 2 cylinder low RPM harsh firing pulses, extended drive shaft angle, & no wheel loading.


D.R. ___
Sent from my rotory dial wall phone!
#996382 - 09/08/17 03:35 PM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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Originally Posted By: MontanaBud

I examined the exterior of the muffler, but no signs of anything amiss there. I didn't loosen it when removing the rear tire.


If you didn't loosen it, you surely bumped it a bit with the tire along the way. As you re-trace your steps, I'd remove the muffler hanger from the subframe (bolted from the inside) and from the pin on the muffler (clip at the end of the pin) to examine the bushing which rides on the pin and make sure it isn't damaged. No guarantee that it is part of the problem, but it is quick, easy and cheap to fix or rule out.


1995 R1100RSL
#996400 - 09/08/17 07:48 PM Re: Help - High Frequency Vibration [Re: rxcrider]  
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MontanaBud Offline
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Originally Posted By: rxcrider
Originally Posted By: MontanaBud

I examined the exterior of the muffler, but no signs of anything amiss there. I didn't loosen it when removing the rear tire.


If you didn't loosen it, you surely bumped it a bit with the tire along the way. As you re-trace your steps, I'd remove the muffler hanger from the subframe (bolted from the inside) and from the pin on the muffler (clip at the end of the pin) to examine the bushing which rides on the pin and make sure it isn't damaged. No guarantee that it is part of the problem, but it is quick, easy and cheap to fix or rule out.


Okay, I removed the rear wheel, and pulled the bushing from the pin on the muffler. The bolt was a bit loose, but the bushing looked fine. I cleaned up the rubber bushing and lined it with a 5mm latex glove finger, reinstalled everything and went for another ride. Sorry to report, no change.

I think I do feel the buzz a bit more in the right hand than the left, but this handsander-like buzz seems to exist throughout.

Argh!

#996651 - 09/11/17 09:23 PM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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Dobo Offline
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Would bar backs or the risers exaggerate this issue ?
mark

#996653 - 09/11/17 10:17 PM Re: Help - High Frequency Vibration [Re: Dobo]  
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dirtrider Offline
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Originally Posted By: Dobo
Would bar backs or the risers exaggerate this issue ?
mark


Evening mark

They can sure effect it, depends on how it effects/changes the excitation periods. Might make it worse, but could just as easily make it better.

On the 1200 hexhead I actually remove the 4th handlebar attachment bolt (only use 3) then space the bars up on very thin stainless washers to provide a tuned hinge point. That tuning coupled with heavier bar end weights changes the tuning enough to allow most of the boxer buzz to dissipate & not get to my hands.


D.R. ___
Sent from my rotory dial wall phone!
#997821 - 09/26/17 05:13 PM Re: Help - High Frequency Vibration [Re: dirtrider]  
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Dobo Offline
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Originally Posted By: dirtrider
Originally Posted By: Dobo
Would bar backs or the risers exaggerate this issue ?
mark


Evening mark

They can sure effect it, depends on how it effects/changes the excitation periods. Might make it worse, but could just as easily make it better.

On the 1200 hexhead I actually remove the 4th handlebar attachment bolt (only use 3) then space the bars up on very thin stainless washers to provide a tuned hinge point. That tuning coupled with heavier bar end weights changes the tuning enough to allow most of the boxer buzz to dissipate & not get to my hands.



that's interesting i cut up 2 3mm rubber pads to sandwich between the risers etc and it made no decernable difference.
will try your fix.
cheers mark

#997881 - 09/27/17 08:40 AM Re: Help - High Frequency Vibration [Re: MontanaBud]  
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AndyS Online
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Hi Dodo, I feel uncomfortable with sandwiching rubber in that application. Those bolts need to be tight.
It sounds like you are trying to deal with a resonant vibration. If you cant fix the source of the vibration (say, for instance loose bolts or some mechanical parts touching each other that shouldn't be - like an exhaust mount against the frame), then maybe playing around with handlebar end weights may be worth some investigation. There are some high mass end weights available.

#997886 - 09/27/17 11:18 AM Re: Help - High Frequency Vibration [Re: Dobo]  
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dirtrider Offline
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Originally Posted By: Dobo
Originally Posted By: dirtrider
Originally Posted By: Dobo
Would bar backs or the risers exaggerate this issue ?
mark


Evening mark

They can sure effect it, depends on how it effects/changes the excitation periods. Might make it worse, but could just as easily make it better.

On the 1200 hexhead I actually remove the 4th handlebar attachment bolt (only use 3) then space the bars up on very thin stainless washers to provide a tuned hinge point. That tuning coupled with heavier bar end weights changes the tuning enough to allow most of the boxer buzz to dissipate & not get to my hands.



that's interesting i cut up 2 3mm rubber pads to sandwich between the risers etc and it made no decernable difference.
will try your fix.
cheers mark


Morning Mark

I doubt that you are going to isolate it out & still retain a safe connection so you are probably going to have to tune or absorb it out best possible.

The boxer engine buzz it what it is so not much you can change on that.

To turn the bars into tuned absorbers you will probably need to play with bar end weight & bar excitation frequency. (ie add flex to bar attachment & add mass to end of bars)-- If the triple tree is buzzing but the bar ends are dead then you know it is working as a tuned absorber)

Buy some strips of stick on wheel weights & wrap those around the existing bar end weights to see if you can work up a mass on the bar ends that is enough to help. Use that in conjunction with different iterations of 3 bolt bar attachment on thin washers. If you get something working then weigh the new bar end weights then see if you can make or buy something in a similar weight.

On some of my dirt bikes (known for very buzzy bars) I foam fill the center of the tubular bars then add lead bird shot to the outer ends to deaden the buzz. Works pretty darn good but not easily done on the BMW RT bikes.


D.R. ___
Sent from my rotory dial wall phone!
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