I have an 85 V65 Magna.  I restored it top down, but I have a vibration problem that I can't seem to fix.  When the tach hits between 4500 and 6000 RPM I get the vibration.  The best way that I can describe it is that it feels like riding on blacktop at about 50 MPH on knobby tires.  I have done all of the obvious things (i.e. new tires, balanced tires, tighten motor mounts, etc.), but nothing works.  I strongly beleive that the vibration is caused by the engine because I can pull in the clutch and the vibration completely goes away.  Speed doesn't matter.  25 MPH or 65 MPH, the vibration is there whenever the tach is between 4500 and 6000 RPM.

Any help that you could provide would be greatly appreciated!  

If it's engine related, might be needing a good carb rebuild, maybe has a spark box that's going?  Go to v4hondabbs.com, there's a bunch of V4 experts there that can help you out.