Vibes after a U joint install

[Petrus Rocks]

I have a modified Cal II.  The U joint was suspect so Rough Edge and I replaced the U joint, boot, and bearing with a kit from MG Cycle.  Regardless of the gear, at 60 mph there is a pronounced rhythmic vibration.  Previously the rear end was vented.  The vent was spraying gear oil so i plugged it.  No issues previously ( last two years).
 I think it is the U joint or bearing.  Thoughts?

[LowRyter]

I've heard that if you reinstall the u joint and turn it over 180 degrees, that it will sometimes cure vibration.   ("Heard" meaning that I have no experience.)

[randy yocum]

A new U-joint and new bearing,there should not be any vibration.I hope that helps
   No seriously,can you tell if the bearing seated properly in the swing arm boss(I think that's what you call it)I've done several,it (the bearing)should be an interference fit,like very tight.I'm thinking what if the bearing is slipping in that boss area,or the bearing is cocked some how wouldn't that cause vibration?That's my 2 cents

[guzzisteve]

It's the bearing. Go to bearing supply and get the best SKF, FAG, no Chinese all balls. I have never had a new joint bad. Use the old bearing to install the new one, no damage and clip goes right in.

[guzzisteve]

I've heard that if you reinstall the u joint and turn it over 180 degrees, that it will sometimes cure vibration.   ("Heard" meaning that I have no experience.)

I have done it before, sometimes it helps. I guess more in tune w/trans shaft. You could also flip around the collar on the shaft, tried that to.

[Petrus Rocks]

Thanks guys.   A bearing is cheaper than a U joint.  I can try that first.

[Rolf Halvorsen]

Has the U-joint been seated deep enough in the bearing?

[Two Checks]

Make sure a header pipe isn't touching the frame.

[Petrus Rocks]

I don't think it would go back together if the joint wasn't seated well enough.  Initially had that problem.  Not ready to pull it apart yet.  Rebuilt a Norton and seized a piston on the third ride..  My Triumph decided to leak oil out of various orifices and then there are the vintage race bikes and the Buell needing some attention.  I'll order the bearing and tear it apart soon.

[Rolf Halvorsen]

We are talking about millimeters here. When the U-joint rotates in an angle - the lenght of the U-joints changes a little bit.

[Rough Edge racing]

 I can't imagine a few MM's short of seating fully could make the joint run out of true ?   This story has a bit of history....A friend bought this bike and I was "hired" to turn it into a cafe racer...That I did and also replaced all the bearings and serviced the driveshaft...First Guzzi I worked on.....The u joints were worn...As was the double U joint carrier, the holes were a bit egg shaped , the bearing cups loose.. For some reason there were no complete u joint assemblies available at that time so I just bought two u joints...I used JB Weld epoxy on the loose cups.....The bike then went to the land speed racing track in Ohio along with my vintage Triumph race bike...Both bikes set a track record...The stock 100,000 mile Guzzi engine with no mufflers and a bit of jetting work ran four consistent passes at near 118 mph in the one mile standing start...Then my friend traded me the Guzzi as payment for work on some other bikes...I rode it around for about 500 miles, then I met Pete he he liked the bike and bought it from me...Pete made changes to his liking and rode the bike maybe another few thousand miles...Pete like to ride in a "sporting" manner so it was not exactly easy miles....He knew about the glued U joints so it seemed wise to change them...When removed the glued joint was still tight....

[brider]

He knew about the glued U joints so it seemed wise to change them...When removed the glued joint was still tight....

Still trying to visualize where the JB Weld was used, but man, what a testament to it's toughness! I was tempted to use some in my own Cal 2 Auto driveline, but went a different route...

And for nerds like me who nit-pick a lot, a millimeter is just about .040 inch, a HUGE amount for a carrier bearing to be out-of-alignment, and probably not even possible. You're probably talking in the .001-.010 inch range if the bearing was not seated completely, but then you wouldn't be able to install the circlip in the swingarm, would you? .001-.010 inch = .0254 - .254 mm.

[Rough Edge racing]

Still trying to visualize where the JB Weld was used, but man, what a testament to it's toughness! I was tempted to use some in my own Cal 2 Auto driveline, but went a different route...

And for nerds like me who nit-pick a lot, a millimeter is just about .040 inch, a HUGE amount for a carrier bearing to be out-of-alignment, and probably not even possible. You're probably talking in the .001-.010 inch range if the bearing was not seated completely, but then you wouldn't be able to install the circlip in the swingarm, would you? .001-.010 inch = .0254 - .254 mm.

  The epoxy was applied sparingly around the cups and the insides bores of the carrier where the cups get pressed into...I would say the bores were worn a few thousands of an inch egg shaped and had no press fit..Usually on a hillbilly repair like this on a vehicle I tack weld the cups but it didn't seem appropriate here...
 Anything is possible but the carrier bearing is a press fit and if it lacks .040 of being home,in my opinion, there's no way it could be cocked...But the new part may not be machined accurately or a bad bearing etc...Then there's the rear drive blowing gear oil from the added on vent hose that didn't blow oil before the u joint replacement...No oil was lost or added during the work..

[Petrus Rocks]

We did change oil because I figured I might as well.  Per manual specs.  The pressure increase in the rear end is puzzling.  First ride there was oil everywhere...

[Rolf Halvorsen]

The U-joint consist of 3 parts.

When you do a 360 degrees rotation you will see that the total lenght of the U-joint is at its maximum.

Bend the U-joint as it normally is when you install it on the bike - and the total lenght is considerable shorter.

If the U-Joint is not assembled deep enough in the bearing - then you might have a problem with the U-joint colliding with the axle on the gearbox layshaft.