Question

[lucky_1_chris]

Had my bike on on the lift a couple weeks ago investigating a clunk in the rear end. While it was up, for whatever reason, I decided to run it through the gears. In fifth at around 3k rpm's, the bike started shaking quite a bit. Didn't worry about that much 'cuz the wheel is really moving at this point, but a couple hundred RPM's later it started clunking and clanging something good... I wrote it off to slack in the driveline/trans amplified by the wheel being off the ground and loose, but I'd like to hear what you guys think about it. Normal and nothing to worry about, or am I doomed?

[alph]

i'd take is seriously, that is, if it were my bike......  there shouldn't be vibration and clunking in a shaft drive machine, period, i don't care if it's a lawn mower, that shouldn't be making that sort of noise.

tear into your drive line, i'd bet it's your uni-joint.

[Gryphon Rider]

Here's my theory:
When the back wheel is allowed to hang low, it puts an angle in the u-joint.  Whenever a u-joint (as opposed to a c-v [continuous velocity] joint) is at an angle, the driven end does not spin at a continuous velocity, but spins fast-slow-fast-slow every revolution.  When this happens temporarily when the bike is travelling down the road, such as when you crest a hill faster than you should and you almost separate from the seat, the tire's contact with the road prevents the wheel from going fast-slow-fast-slow with every revolution of the drive shaft.  Instead, this fluctuation is absorbed by the drive shaft, which is under constant load, and the wheel dampers (those five blocks of rubber connecting the drive flange with the rim).  When this happens with the wheel off the ground, the wheel is allowed to go fast-slow-fast-slow, and if this frequency resonates with the natural frequency of the wheel/damper assembly, it will start to really hammer.  This could have done damage to one or more of any number of components within the drive train, including the u-joint.  I don't have the experience to tell you how likely this could be.  I hope I'm wrong, for your sake.

[9Ball]

I'll buy that...good reasoning.

Definitely wasn't a wise thing to do....live and learn.

[John Schmidt]

Son, you like living kinda dangerous apparently....running your bike up to 3k in gear on a lift. That's not the most stable platform for doing such things, plus you talked about vibration which makes it even less stable. 

[Chrisj CMA]

Had my bike on on the lift a couple weeks ago investigating a clunk in the rear end. While it was up, for whatever reason, I decided to run it through the gears. In fifth at around 3k rpm's, the bike started shaking quite a bit. Didn't worry about that much 'cuz the wheel is really moving at this point, but a couple hundred RPM's later it started clunking and clanging something good... I wrote it off to slack in the driveline/trans amplified by the wheel being off the ground and loose, but I'd like to hear what you guys think about it. Normal and nothing to worry about, or am I doomed?

Were the shocks both attached or was the swing arm hanging free or tied up by a strap?  The drive train on a Valkyrie is not designed to rotate with the swing arm in any other position  than full up where the shocks are attached. 

[sutterhome]

when i changed my rear tire last summer I noticed the tire wont rotate when its hanging on its own weight, or very cluncky at best.My 2 cents

[lucky_1_chris]

Had my bike on on the lift a couple weeks ago investigating a clunk in the rear end. While it was up, for whatever reason, I decided to run it through the gears. In fifth at around 3k rpm's, the bike started shaking quite a bit. Didn't worry about that much 'cuz the wheel is really moving at this point, but a couple hundred RPM's later it started clunking and clanging something good... I wrote it off to slack in the driveline/trans amplified by the wheel being off the ground and loose, but I'd like to hear what you guys think about it. Normal and nothing to worry about, or am I doomed?

Were the shocks both attached or was the swing arm hanging free or tied up by a strap?  The drive train on a Valkyrie is not designed to rotate with the swing arm in any other position  than full up where the shocks are attached. 

Yes, the shocks were on

[Ricky-D]

Gryphon Rider has it correct!

You put a abnormal load upon the drive train.

Hopefully no damage occurred.

Not to mention how dangerous doing so!

***

[Chrisj CMA]

when i changed my rear tire last summer I noticed the tire wont rotate when its hanging on its own weight, or very cluncky at best.My 2 cents

You should never let the swing arm(and wheel) hang on its own weight.  What IT is hanging on at that point is the u-joint.  As the U-joint takes up all that weight in a way it was not designed it is entirely possible to damage the joint and cause it to have an early catastrophic event.  Use a strap to hold the swing arm up so its not resting on the joint

[lucky_1_chris]

Son, you like living kinda dangerous apparently....running your bike up to 3k in gear on a lift. That's not the most stable platform for doing such things, plus you talked about vibration which makes it even less stable. 

It was tied down good...wasn't going anywhere...but you're right. Wasn't the smartest thing I've ever done.

[lucky_1_chris]

Here's my theory:
When the back wheel is allowed to hang low, it puts an angle in the u-joint.  Whenever a u-joint (as opposed to a c-v [continuous velocity] joint) is at an angle, the driven end does not spin at a continuous velocity, but spins fast-slow-fast-slow every revolution.  When this happens temporarily when the bike is travelling down the road, such as when you crest a hill faster than you should and you almost separate from the seat, the tire's contact with the road prevents the wheel from going fast-slow-fast-slow with every revolution of the drive shaft.  Instead, this fluctuation is absorbed by the drive shaft, which is under constant load, and the wheel dampers (those five blocks of rubber connecting the drive flange with the rim).  When this happens with the wheel off the ground, the wheel is allowed to go fast-slow-fast-slow, and if this frequency resonates with the natural frequency of the wheel/damper assembly, it will start to really hammer.  This could have done damage to one or more of any number of components within the drive train, including the u-joint.  I don't have the experience to tell you how likely this could be.  I hope I'm wrong, for your sake.

No evidence of any damage yet. If I damaged the u-joint I'd probably know it by now...it's been a few weeks. Ill know more when i change the tire, but everything feels fine so ill bet im ok. Didnt run it like that very long at all. I had no idea i could hurt the bike by doing that (aside from it falling  from the lift...). It wasn't a hard clunk or anything like that, sounded more like the noise the bike makes in neutral with the clutch out, just louder. Hope that makes sense.

[Ricky-D]

You know, this is a real interesting thread and it has answered a question that has been bothering me for a long time.

When my u-joint was going bad, it was not noticeable at the first.

The first inkling that there was a problem was when I was cornering the bike in a slow turn. There was a clunky noise and the accompanying clunky feel.

Now this thread explains why that was.

In a cornering turn, with the bike leaning, the swing arm is unweighted and that allows the angle of the drive line to increase thus making the u-joint come more into play. Much like the bike sitting on the jack.

If you have an opportunity to look at the angle of the drive line when you are seated, you will find it is pretty much for the most part straight in line.  So when normal riding you will not feel any problem with the u-joint. That is until it is completely shot!

So if you feel something when making a slow speed leaning turn or curve, don't discount the u-joint. Be a good idea to have a new u-joint in reserve.

***

[indybobm]

I'm planning on doing driveline maintenance this winter. After reading this thread I have some questions.

Let’s say, you are removing the rear wheel with the bike on a lift, the shocks have been removed and the bike raised on the jack high enough to give enough fender clearance to allow the rear wheel to be removed. Sounds like when the bike is in this position, the rear wheel should not be rotated, is this correct?

By dropping the swing arm enough to remove the rear wheel, will this damage the u-joint if the wheel is not rotated?

With the shocks still attached and the rear wheel is off of the floor, is it ok to rotate the rear wheel?
 

[Gryphon Rider]

In a cornering turn, with the bike leaning, the swing arm is unweighted...

Actually, in steady state cornering, the centripetal force of the ground pushing laterally on the tires ADDS to the vertical normal force of the ground counteracting the weight of the bike.  Those two forces add to a diagonal force, in line with the leaning bike.  This compresses the suspension more than it would be while riding a straight line.  With a tighter corner (such as u-turns) the front wheel is affected (and thus its suspension compressed) more than the back wheel.

The suspension decompression that happens when the bike straightens out can be a lot of fun when demonstrating a tight slalom with a little dirt bike.  When I really carve the corners, I can make the front tire lift right off the ground between corners!    The sensation is similar to skiing moguls, when the tails of one's skis lift between turns.

[Hoser]

When removing the rear wheel, take the rear section of the fender off, rolls right out the back, and it's easy to remount the fender half.    hoser

[Chrisj CMA]

I'm planning on doing driveline maintenance this winter. After reading this thread I have some questions.

Let’s say, you are removing the rear wheel with the bike on a lift, the shocks have been removed and the bike raised on the jack high enough to give enough fender clearance to allow the rear wheel to be removed. Sounds like when the bike is in this position, the rear wheel should not be rotated, is this correct?

By dropping the swing arm enough to remove the rear wheel, will this damage the u-joint if the wheel is not rotated?

With the shocks still attached and the rear wheel is off of the floor, is it ok to rotate the rear wheel?
 

For the question about damage to the U-Joint just by dropping the swing arm.........Yes and NO.  

If you remove the shocks and let the swing arm and wheel rest hanging down on its own weight YES, you can over stress the swing arm.

Here is the easiest way to do it (If lowering the swing arm is what you want to do).....remove the left (brake side) shock and attach a tie down strap to the swing arm.....I just slip the hook in the hole the lower bolt came out of.  Then hook the other end of the strap to the sissy bar, and snug it up.  Now when you remove the right shock the swing arm will only drop the amount of stretch that the strap provides and is usually just enough to clear the pipes.  Magic!

BTW.....dont let the strap go across the passenger seat. (or either seat) the padding will allow too much drop and could damage the seat.

[HayHauler]

I don't know about other's bikes, but when I remove both shocks, my swingarm will not go all the way down.  The acorn nuts on the exhaust (left side) hit the swingarm and stop it from falling to the bottom and damaging anything. 
I have run it through the gears in this position, but not to top speed.  I got the rear tire going about 30 mph in 5th and then returned the tranny to neutral.  It started clunking a bit, but I imagine not as bad as if it was all the way to the bottom.  This puts the u-joint in a bind and is not a good idea.

Oh, yea, I only did this once and have changed out the u-joint since then.

Hay 
Jimmyt

[Chrisj CMA]

I don't know about other's bikes, but when I remove both shocks, my swingarm will not go all the way down.  The acorn nuts on the exhaust (left side) hit the swingarm and stop it from falling to the bottom and damaging anything. 
I have run it through the gears in this position, but not to top speed.  I got the rear tire going about 30 mph in 5th and then returned the tranny to neutral.  It started clunking a bit, but I imagine not as bad as if it was all the way to the bottom.  This puts the u-joint in a bind and is not a good idea.

Oh, yea, I only did this once and have changed out the u-joint since then.

Hay 
Jimmyt

Jimmy, You kinda missed the point.

Those that want to remove the axle under the muffler actually move the exhaust out of the way so those acorn nuts dont hit the swing arm (paint damage also happenes where they hit)

I now raise the swing arm and pull the axle out above the exhausts but thats just personal choice.

[HayHauler]

Yea, I knew that, but I don't mind the swing arm hitting the exhaust and removing a little paint.  It is mostly hidden by the bags on the IS.  Mine even clanked pretty bad only being lowered to the point that the exhaust nuts hit.  I would think that the damage would be real with the swing arm at the bottom of its travel.

But I do see your point.

Seems easier to me to pull the axle above the pipes, but I'm weird sometimes. 

Hay 
Jimmyt