Motorcycle shaking after sprocket replacement

[alexisonfire]

I swapped the front 15-tooth sprocket out for a 14-tooth yesterday.  Reinstalled everything correctly, set chain tension and aligned rear wheel.

Took the motorcycle out for a ride and noticed a strong vibration in the handlebars and sometimes even in the footpegs.  The vibration is noticeable when I slow down with the clutch lever pulled in.  I tested it with and without the brakes and occurs in both instances.  As I decelerate there is an on/off buzzing that occurs.  It happens at 40 and stops at 30 then begins again at 20 and so on.

My best guess is the rear wheel is not aligned properly. 

I have never loosened the rear axle nut on the bike so I took care to notice that the rear alignment indicators were in identical positions according to the swingarm tick marks.  After setting chain tension with the left adjuster, I adjusted the right to match.  They appear to be identical.  I think the rear right may be just a hair forward.  I assumed it was not off by enough to create any kind of problem.

Anybody have a foolproof way of measuring rear axle alignment?

Any ideas?

[ducpainter]

I swapped the front 15-tooth sprocket out for a 14-tooth yesterday.  Reinstalled everything correctly, set chain tension and aligned rear wheel.

Took the motorcycle out for a ride and noticed a strong vibration in the handlebars and sometimes even in the footpegs.  The vibration is noticeable when I slow down with the clutch lever pulled in.  I tested it with and without the brakes and occurs in both instances.  As I decelerate there is an on/off buzzing that occurs.  It happens at 40 and stops at 30 then begins again at 20 and so on.

My best guess is the rear wheel is not aligned properly. 

I have never loosened the rear axle nut on the bike so I took care to notice that the rear alignment indicators were in identical positions according to the swingarm tick marks.  After setting chain tension with the left adjuster, I adjusted the right to match.  They appear to be identical.  I think the rear right may be just a hair forward.  I assumed it was not off by enough to create any kind of problem.

Anybody have a foolproof way of measuring rear axle alignment?

Any ideas?

A tape measure from the swing arm pivot to the axle works on my DSS Monster.

[Chchadder]

Yeah, as soon as the rain is done I've got to get out and do some chain maintenance.  It's been a while since I sighted up my rear wheel alignment.

[alexisonfire]

Is this vibration a common symptom of something?

[Jarvicious]

Did you get the right size sprocket?  How good of shape is your chain?  When I used to work on bicycles, I'd almost always recommend a chain replacement with any gear replacement because the chain and the gears get worn at an equal rate, so if you swap one thing, it won't mesh properly with another.   

Have you tried to stand up on your pegs and relieve a little weight off the rear shock/wheel?  That may tell you whether or not it's a problem with your rear wheel or your newly installed sprocket. 

[Sleeper_I]

If you didn't, be sure to clean out the crud-build-up behind the alignment indicator / tick marks before remeasuring. It gave me a false reading.... by 3/4 of a turn Yea, I should clean my monster more often

[wiggy_nz]

Loosen the chain a bit and try again.  If the chain is too tight it will cause this vibration.  Thirtyseven years of riding bikes is my experience.  Try it....you will like it much better   the chain I mean. [moto]

[Howie]

First, check the condition of the chain and make sure the sprocket is tight and the retaining plate is not worn, allowing the chain to walk to much.  The front sprocket may also have the wrong offset. Compare it to the origional.  Also look at the wear on the old front sprocket.  Then  check the chain tension, actually add some.  Too loose is better than too tight.  While adjusting tension, check the rear wheel alignment.  I use ducpainter's method for alignment.  Here is another method, scroll to the end where Chris puts the wheel back on the bike.
http://www.ducatitech.com/info/wheelchange.html

[Duck-Stew]

Adding to the wealth of knowledge above:

Chains can also get tight spots and loose spots.  Try rotating the wheel around (you can wheel the bike forward/back on the ground to do this) and see if the slop in the lower run of the chain changes.  If it does, you could have set the tension properly in a looser part of the chain and then you're getting a binding when the tighter part rolls around.

And a BIG +1 to swapping both sprockets and the chain at the same time.

[alexisonfire]

The bike has 4900 easy ridden miles on it.  I've been meticulous with chain maintenance.  The condition of the original front and rear sprockets is very good.  No irregularites, the teeth show little wear.  The front sprocket retaining plate has minimal wear.

I think you guys are correct about the chain being too tight.  I'll reduce the tension and report back tonight.  If the problem persists I'll probably just buy a new rear sprocket and chain.

This is the sprocket I just put on the front:
http://www.drivesystemsusa.com/p/291863/afam-520-chromoly-steel-countershaft-sprocket---ducati-.html


Thanks.

[Norm]

Maybe the rear cone shaped washer in backwards?

[Spidey]

I'm putting my money on your chain being too tight.  Super common problem.  Better to run it on the looser side, even if it is looser than factory spec (which is what i had to do with my 1000).

And don't use the swingarm marks.  They are notoriously off.  I've tried a buncha different methods to assure I have the right alignment.  I've finally settled on just looking down the chain and making sure it's lined up with the front sprocket.  It's totally imprecise, but so far it works better than any other fancy schmancy way of doing it.  Sometimes, if I'm feeling all technical n' stuff, I lay a piece of 1/2" (?) bar stock (got it at the hardware store for precise this reason) along the rear sprocket and then see if it lines up with the chain. 

BTW, check your wheel weights.  They still there?

[alexisonfire]

The rear cone spacer was in the correct position.  Wheel weights are still in place from last tire replacement by Ducati dealership.

I'll give this bar alignment thing a shot.  Oh, and I'll reduce the chain tension as well.

Thanks.

[ScottRNelson]

Don't skip the step of checking for tight spots.  If your chain has stretched unevenly, and making it too tight can do that pretty quickly, you'll never get the bike to be smooth until you get a new chain.  I had an unevenly stretched chain on my ST2 that still looked perfect, but I replaced it to smooth things out.

Also, if you happen to have a 42-tooth rear with a 14-tooth front, that is an exact multiple of three and you'll get some strange harmonics from it at certain speeds.  Been there, done that on my ST2.

[alexisonfire]

Set the tension at the point of least 'slop'.  Gave it a fair bit more play than before.  Eyeballed the chain to see it was aligned.  Wheel appeared to be centered.

Took it out for a ride and no more vibration.  Problem solved.

As for the difference between the 14T and 15T,  the bike runs like a bat out of hell now.  Pulls so much more effortlessly in 3rd - 5th gear as well.