Rear Isolators
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Road Master
Joined: Jul 2008
Posts: 859
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From: In the mountains
Rear Isolators
1992 FXR. Getting a lot of vibration after replacing the rear isolators and the front motor mount, as well as the the stabilizer links. Links were installed before changing the rubber mounts. As for the front mount, I left it loose took the bike for a ride to settle in and then torqued everything per the manual. At 40lbs of tq on the center bolt for the front mount, lots of vibration. At 10 ft lbs, better riding, but still vibrates badly at low speeds. Which leads me to the rear isolators, I think. What could go wrong changing them? When I replaced them it was pretty straight forward. Had to get a pry bar under the trans to slide the swing arm bolt back in, but was not a big deal. I'm stumped.
I still have the factory donuts on the back of mine, but did replace the front mount a year ago or so.
Like you, I noticed a very different vibration pattern. In my case, it was smoother at highway speed, but shook like crazy right at 1,000 to 1,100 RPM.
I lowered my idle speed a smidge to get just under the "bad spot", and also had good results from running the set screw on the mounting bolt on the loose side.
It also seems like it has eased up with time and miles, but that may just be faulty perception on my part.
My sense of these things (mostly intuition, since I've got limited direct experience) is that each different isolator has it's own personality. We are dealing with fairly complex vibration harmonic effects, and depending on conditions, even minor manufacturing variances in the isolators can create outsize impacts.
Which is my long-winded way of saying run it for a few thousand miles and see what's what.
Like you, I noticed a very different vibration pattern. In my case, it was smoother at highway speed, but shook like crazy right at 1,000 to 1,100 RPM.
I lowered my idle speed a smidge to get just under the "bad spot", and also had good results from running the set screw on the mounting bolt on the loose side.
It also seems like it has eased up with time and miles, but that may just be faulty perception on my part.
My sense of these things (mostly intuition, since I've got limited direct experience) is that each different isolator has it's own personality. We are dealing with fairly complex vibration harmonic effects, and depending on conditions, even minor manufacturing variances in the isolators can create outsize impacts.
Which is my long-winded way of saying run it for a few thousand miles and see what's what.
How did your mounts look when you took them off? I was surprised to see that my front was cracked clean through, about 180 degrees around the hole.
Seasoned HDF Member
Joined: Apr 2011
Posts: 6,185
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From: W. Texas
When I replace the rear isolaters with an upgrade kit I noticed a bit more vibrations. It made sense with things being tightened up back there the vibration was worse. You have made a more solid path for the vibration to travel to the frame.
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Seasoned HDF Member
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From: W. Texas
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