Whoom, whoom noise in 5th between 40 & 50mph

[birdman]

2011 Triple Black 1200GS, now has 7,500 miles. Since new it has made a whoom, whoom noise in 5th gear between 40 & 50 mph. Drop below 40, or accelerate above 50 and the noise goes away. Pull the clutch in and the noise goes away! Change into 4th or 6th and the noise goes away. Makes me think it's a transmission problem, someone speculated it's a bad 5th gear not quite meshing properly. I'm having a challenge getting BMW to investigate the problem and resolve it under warranty - they have 1. suggested that the noise in an acceptable limits (not sure how they define acceptable), and 2. advised the dealer to document the complaint so there's a record of it in the future if there's a major failure. Question to forum members has anyone suffered from this annoying noise, or heard of others who have reported the problem and then got it fixed.

[pdxrmccgs]

I have not seen anything like it on the forums. Usually the complaint
is "clunkiness". Here is some animations which might help in the
diagnosis:

How a motorcycle gearbox works - YouTube

My only 2 cents would be it sounds like the dogs are spinning
against the side of the gear. Does it happen at all RPM's
when shifting into 5th gear mmmm...just re-read your post
...maybe it is disengaging 5th gear at those speeds.

Let us know what you find out. Maybe someone with same
problem will post.

Welcome to forum.

[marc]

If it's the type of noise I'm thinking about it may be due to the harmonics from different noise sources, say the engine and the transmission, that are almost in sync, but not quite. Also, before you go blaming your transmission remember that when you pull the clutch in while the bike is in motion the transmission does not stop moving... it just gets driven by the rear wheel instead of the engine.

Documenting the possible issue as you have done is probably the best thing to do. Don't be surprised if the noise changes or even goes away when you do something that you'd think isn't related, e.g. change tires.

[pdxrmccgs]

+1 on tires. One of the great mystical facts about auto-moto
maintenance is how speed related noises are tire caused.

[portablejohn]

I have an '11, and I have noticed a similar noise. I am going with the theory that is some sort of harmonic effect, and not some mechanical flaw.

Here is a link to something that (kind of) describes what I think is happening:
Constructive and Destructive Interference

I tried to tune a piano once, and as I got very close, but not quite, I could hear the two (of three) strings I was tuning to the same note start to pulse as the peaks of the waves started to match up.

On a side note, drive in a lower gear? I live on the DelMarVA peninsula, where it is basically flat. I find myself riding in a higher gear than I should. I have trained myself not to shift up between certain towns. I'm pretty sure you can do 50mph in third gear without coming close to red line. Coming from a inline 4 (Concours), I have a hard time running this engine fast enough...


John

[HerndonP]

Have you replaced your tires recently? I get the humming noise from my Anakee 2 tires between 45-55 mph.Sounds like transmission,but its the new tires.

Pete

[pdxrmccgs]

JVB on harmonic vibration..

Harmonic Vibration @ 4000-4100 RPM on 1200 GS - ADVrider

[mikec]

Pete (HerndonP) mentioned his Anakee IIs are making a similar noise. In August, I was in the middle of a trip and stopped by a BMW dealership close to my route for some new "shoes." I had a set of EXPs put on and promply jumped on the interstate, riding about 500 miles.

I noticed the "whoom whoom" noise almost immediately. I just returned from a trip from NC to Tucson and back so the EXPs now have about 6500 miles on them, still making that noise. By the way, it's most noticable in the 40-50 mph range.

Mike