Harmonic Vibration Under Load

[Coot]

Good evening:)  I have a vibration in all five gears.  It goes away at about 3,500 rpm.  it manifests itself as a loud hum, not quite a roar.  At 3,000 rpm it does not manifest itself in fifth until I roll on the throttle and continues to hum or roar up to 4,000 rpm.  Roll off of the throttle and maintaining 4,000 rpm seems to quiet the vibration.  A u-joint was installed about 2,000 miles ago.  Also, cruising in fifth at 3,000 rpm is smooth with no vibration, but any application of throttle brings the vibration back.  I hope I have described this in such a way as to help you mechanics out there to diagnose this problem.  Please help.

Thank you,
Coot

P.S.  It feels like something is grinding away.  BTW, final drive has recently been serviced.

[Savage]

Was the U-joint you installed brand new Honda OEM?

Is there a possibility you have a bent or poorly balanced wheel?

What tires are you running and how much wear?

[Chrisj CMA]

I would take it apart and see what that pinion cup looks like

[gordonv]

3 things, u-joint, pinion cup, and rear bearing.

It almost sounds like it's not the bearing, due to only under load.

So either u-joint or pinion.

Did you do the work yourself?

My guess is with ChrisJ, the pinion.

If you aren't riding right now, I would take it apart and inspect. But considering what might happen, I wouldn't be riding it without knowing.

[Coot]

Thanks for taking the time and for the advice.

Coot

[Bighead]

I would ride it. I have heard/felt (Not really a vibration but similar under load) the same for some 23 yrs now and guess what? She still is strong without problems.

[Coot]

Thanks, Bighead.

[Jess from VA]

Could this be the buzz bolt? 

http://www.valkyrieriders.com/shoptalk/buzz.htm

[Gregory Scott 16248]

Could this be the buzz bolt? 

http://www.valkyrieriders.com/shoptalk/buzz.htm

I agree sounds like the buzz bolt. Tighten up both ends.

[Jess from VA]

I did mine years ago.  I think the nut head is left and the bolt right.  You can't hold a tool on both sides at the same time.  But you crank the right nut, you don't need to put a tool on the left bolt head, it doesn't turn.  With an interstate, you either pull the pod, or use a ujoint up through the pod side vent (careful, it is  easy to damage the pod plastic if you slip).  

I cranked pretty hard the first time, but the rattle continued.  The second time I cranked as hard as I could, with hard metal squealing jerks.  It's tool steel and didn't break anything.  I also think I actually slightly bent the frame members inward to capture the long spacer around that bolt inside the frame.  It never rattled again.  I think the rattle is actually the long spacer inside the frame, not the bolt at all.

When that thing gets to buzzing and rattling it's aggravating as hell.

As I recall, the only way to shut it up (before tightening) was to motor around with very little throttle.

[Gizmo]

No amount of wanking on the bolt stopped mine. So I pulled it, coated it with silicone and put it back.
Hasn't buzzed in 10 years. Can't remember where I got the tip from.

[F6Dave]

Could this be the buzz bolt? 

http://www.valkyrieriders.com/shoptalk/buzz.htm

I agree sounds like the buzz bolt. Tighten up both ends.

When you said you hear it in all gears, and it goes away at 3,500 RPM, I thought that sure sounds like that bolt.  The problem is that the frame twists a bit under load and tries to spread the fork tubes apart, so the tube the bolt runs through gets loose, and vibrates.  Some crank it down, while others put a thin washer between one end of the cross tube and the fork tube.  Cranking it down is easier.

[Coot]

More good stuff.  Thanks!

[Smokinjoe-VRCCDS#0005]

Coot ... I'd bet the farm it's not ujoint or pinion cup or bearings . It has brand new ujoint brand new rear bearings and I had the final drive out and serviced less than 100 miles before you bought it. I'd get on that bike right now and take a cross America ride.

[Bagger John - #3785]

No amount of wanking on the bolt stopped mine. So I pulled it, coated it with silicone and put it back.
Hasn't buzzed in 10 years. Can't remember where I got the tip from.

The old Tech Tips area had that particular fix.

Another was to drill and tap the spacer sleeve for small screws then snug them against the bolt after final torquing.

[Jess from VA]

If you get inside, then it seems the easiest fix would be to add a washer or two sistered up to the long spacer inside the frame. Then torque the spacer down tight with the bolt.

Silicone (or other goop) dries out over time and can start crumbling.