Resonating/echoing sound in 5th and 6th gear

[antonijn]

Hi all,

 

First post here.

I bought a second hand '21 T7 with ~6000km on the clock.

It's a much nicer to ride bike than the old XT660Z Tenere, which I also own (`11). That bike now has 65.000km on the clock and is kept in Bulgaria for two-up traveling in the summers. (still a great pack mule)

I love the new T7 and it rides great, I do have one (maybe)issue though.

 

Whenever I'm in 5th at around 3k rpm I hear quite a loud resonating/echoing sound coming from the bike.

If I shift down to fourth and keep riding the same speed it goes away, I also don't notice it between 1st-4th gear at 3k rpm.

I can very faintly hear the same resonance in 6th at 4k rpm and can feel it through the foot pegs.

It only happens when the engine is loaded (at constant speed), so when I let go of the throttle it goes away.

 

I have a set of knobbies (Mitas E09) on the bike but I don't think these cause the sound since it's depended on the gear I'm in and the engine rpm.

There is also an Acerbis chain guide installed, which might be the cause? I'm not sure?

 

Anyway the bike runs fine and accelerates good, so I'm not too concerned about it being anything harmful.

 

Just curious what might be the cause and if there's something I can do about it...

 

[Samm]

I’ve heard this before when cruising at very consistent speed/rpm. I’m sure someone will correct me but I’m pretty sure it’s just the perfect storm of rotating members interacting with wind noise. I’ve always ignored it or just punched the throttle.

Do you ride with earplugs?

[antonijn]

Thanks for the reply.

Yeah I always ride with earplugs, and I can hear it.

 

I'm sorry but I'm not quite sure what you mean by "the perfect storm of rotating members interacting with wind noise", could you elaborate?

[Alsoran]

I don't know if it could be a similar issue, but I had a noise at about the same RPM / and gear selection after I installed the OEM chain guide. The strange thing is I did not notice it right away, but one day I was riding a highway near a retaining wall and heard a loud "howling" noise. I could change gears and it would go away. The bike was running fine otherwise.

 

I remembered that I had recently installed the chain guide. I decided to take it off and I have not heard the noise since. I'm about to put the chain guide back on for a ride so I may be able to confirm if that is the noise problem. 

 

Possible effects: chain guide and the chain at a certain tension makes a noise under specific loads? Include a dry chain? Or perfectly adjusted chain with chain lube and no noise?

 

Could be why they don't have the chain guide installed on a new bike.

Edited June 8, 2023 by Alsoran

[Jesse]

My bike does the exact same in 5th gear same RPMs. I have 20,000 miles on it now even with a new chain, sprockets, and tires still has the 5th gear resonating sound.  I just assume it's normal and the engine drivetrain hitting the right combination causing it to sing.

[antonijn]

Small update:

 

I haven't really been able to ride yet. But it seems that when I'm hanging my head to the left side of the bike that the sound is louder in my left ear than in my right ear.

Indicating that it might very well be the Acerbis chain guide. I'll remove it in some time when I feel like it and when I have time and see if it makes a difference.