Heavier flywheel?

[Barry]

Keep track of the motor mount torques and play with the values a bit, maybe between 55-45 ft lbs.It will move/change the high end vibration band

That worked for me moving the vibration up to revs I very rarely use.

Vibration is at a low enough level that I don't notice or think about it any more on a daily basis. Can't say that about any other bike I've had.  Like the man said go ride an A65 or any other 60's/70's British twin except perhaps a Commando and that vibrated away as well, you just didn't feel it.

[livingdeadhead]

don't get me wrong tho! i love grumbly old twins , i actually bought my r65 for its character and characteristics , but i wanted to be reasonably certain of getting where i was going !

[quixotic]

It's getting curiouser and curiouser.  The typical high frequency buzz around 4 grand is still there, but it's minor and I can easily live with it.  And at 5 grand, everything is as smooth as butter.

But this other vibration seems to be at a significantly lower frequency, so I'm guessing that it's somewhere in the drive train (either the shaft drive or the rear wheel).  But the crazy thing is that it's intermittent.  In a 20 minute drive, it'll surface for a couple of minutes and then disappear.  But when it's there, it seems like something is in danger of tearing itself apart.  

Any guesses?  I think my next task will be to raise the rear end, spin the wheel by hand, and see if I can detect anything strange.

[quixotic]

I'm glad I had a look at the rear end.  I had assumed that since the tranny and engine fluids were clear and at the precisely right levels (from the previous owner), the drive shaft and differential fluids would be also.  Nope.  They were dangerously low.  Now that they're topped up, I'll do a fluid change soon and hope that I don't find any filings.  

And even though I recently adjusted the tappets, I do detect a significant difference in sound from left to right.  So that'll be on the imminent to-do list also.  And I assume that any time the tappets are adjusted (when cold), the carbs should then be adjusted after (when hot).

[Barry]

I had assumed that since the tranny and engine fluids were clear and at the precisely right levels (from the previous owner), the drive shaft and differential fluids would be also.Nope.They were dangerously low.Now that they're topped up, I'll do a fluid change soon and hope that I don't find any filings.
 

I wouldn't worry as levels for the drive shaft and final drive are not as critical as the gearbox and many run them deliberately low, particularly the drive shaft to prevent the oil migrating from one part of the transmission to another.