Higher engine vibes at certain revs?

So when I rode the maxim this summer, i noticed that between 5400 and 6300 rpm, give or take, there was definately a more difinitive buzzy feeling. What am I feeling here? I wouldn't pay much attention to it aside form the fact that it sits right at the comfortable crusing speed on the highway.

 

Same problem, 4.8k -> 5.2k, any gear.

 

It's trying to tell you that you're not riding fast enough. Seriously though; do a valve check and adjust it made quite a bit of difference for me and only 3 of the 8 needed adjusting. That is still the XJ's "vibrasonic" range but properly tuned it is much less dramatic.

 

Lots of motors suffer from this "frequency" thing, try riding just above or below. Also check that you have all the rubber shock absorbers in the fins.

 

every material has a resonant frequency. When an external periodic frequency matches this materials natural structural (resonant) frequency, occilation occurs. Say for example an external periodic frequency of 100 hertz (equal to 6000 rpm from an engine) and natural structural frequency of a metal (your frame or casing or a component etc.) being 100 hertz, you get occilation/vibration. This is why the tacoma narrows bridge collapsed, you can tune your guitar through harmonics from another string, and why a tuning fork sounds when its note is sounded.

 

Thanks Lou, that's what I was trying to say.

 

anyone know where to puchase those little rubber fin thingies, what are they called and where should they be placed, i see a few in my engine but believe that several are missing, if not most, think i have one or 2 per side of the engine.

 

They are called ABSORBERS.
8 off......#434-11161-00-00
14off.....#4H7-11161-00-00

 

What's with the $5 difference between the left and right rubber absorbers?? That seems awfully weird to me.