Rattling sound on 955i

[AZSprint]

Howdy all,

Noticed today that my 2004 Sprint ST is making a faint metallic rattling sound (Like a few BB's bouncing around in a tumble dryer).

As far as I can tell, it only happens when rolling off the throttle in gear and under engine braking. I have no idea how long it's been going on as I almost always wear earplugs which hides the noise. Seems fine otherwise and sounds normal when rev'd in neutral and when on the throttle in gear.  

Any ideas what it might be?  

[garry]

Something rattling around in the exhaust?

[AZSprint]

I rode around the neighborhood today and I think that it is coming from the rear wheel area, perhaps a bearing?

[pushr0d]

Bearings tend to make a lot of noises when they go, but chattering isn't one of them.

Maybe your chain is going south; my guess is the rub strip on the swingarm is worn out, and the chain is hitting a bolt head.

[Papa Lazarou]

Sounds good advice-check your chain adjustment first.

Mind you, Triumph Triples and a "rattling sound" are somewhat synonymous.  

[AZSprint]

Bearings tend to make a lot of noises when they go, but chattering isn't one of them.

Maybe your chain is going south; my guess is the rub strip on the swingarm is worn out, and the chain is hitting a bolt head.

You may be on to something. The chain had a bit too much slack. I tightened it and took it for a test ride. The noise has reduced, though I think it's still faintly there, but much less chattering. I'll check for contact between chain and bolt next.

[AZSprint]

Mind you, Triumph Triples and a "rattling sound" are somewhat synonymous.  

Ha! Yes, that's true.   But this sound is definately not engine related. I hear it best at around 30mph with engine off. Seems related to road speed/wheel speed/chain speed.

[nevinfs327]

While I agree it is probably chain related, it is also worth checking out your license plate as the sound you describe is similar to the noise mine made when it was loose.

[AZSprint]

I think it was the chain.

Since tightening it, the sound is very muted and no longer has the metallic "BB in a can" sound.  To help troubleshoot, I mounted my GoPro video camera on passenger footpeg looking at rear sprocket. Even when tightened, the amount of vertical movement of the bottom run of the chain is surprisingly large (at least to me), especially over bumps. Considering that the bottom run of the chain tightens under engine braking, I assume all that slack is now on the top run of the chain as the rear sprocket drives the engine. I think it was that excess slack on the top run that was making the noise.

I'll look closer and see if I can determine exactly what it was hitting. Until then, thanks for the replies  

AZSprint

 

[bubba zanetti]

Sometimes the exhaust bracket can interfere with the centerstand and result in a buzzing/rattle. Just rotate it out of the way of the centerstand and voila

[Croak]

And check your rear brake pads.

[AZSprint]

Sometimes the exhaust bracket can interfere with the centerstand and result in a buzzing/rattle. Just rotate it out of the way of the centerstand and voila

Well done, Bubba Z. The exhaust bracket was indeed in contact with the centerstand. I should have noticed that it always made a metallic clinck when being rolled off the centerstand. Probably like that for years, but I always work on it when it's up on the centerstand, so never saw the contact. I don't think it was the source of this particular noise, but it surely was making a noise of some sort! Gracias for that suggestion.  

And check your rear brake pads.

Worn slightly beyond limits, but not the source of the recently departed sound. Thanks for the suggestion though!