Help With New Noise ...
I noticed a new noise on my 2001 R1100S for the first time today. Starting at between 75 and 80 mph I get a high-pitched metallic humming. It goes away if I slow down. It happens at the same speed, regardless of gear, so I don't think it's rpm / engine related. Brake usage has no effect on the noise, so I don't think it's brake related. The ABS is working fine.
It doesn't come on slowly as I accelerate. It's like a light switch. It's no noise, no noise, no noise, then noise. It doesn't happen every time I reach the speed either. Maybe 90% of the time. It does not change in pitch as I change speeds.
Any thoughts? My first thought is wheel bearings. I think I can eliminate the alternator and alternator belt because it's speed-related instead of rpm related. Right? I don't think it's brakes either. Tires are a thought, but the sound is pretty metallic and it doesn't change pitch or volume when I turn the bike.
I plan to pull the wheel this weekend. Will a bad bearing be obvious using the "stick my finger in the hole and turn it" test? I can't say I've ever felt a bad one.
Thanks in advance,
jim- bad wheel bearing was my first thought too. get the wheel off, put finger inside ID of bearing and spin. should be glass smooth. any disturbance to that motion is bad- gritty feeling, clicky feeling, anything other than dead-smooth is wrong. however, i've got 95K miles on my wheels, stock bearings, perfect.
have you worked on anything in the driveline recently that might effect things?
With any online analysis you have to give us the miles on the bike, 1st owner, 2nd owner, repairs, problems, etc. Otherwise we can't make reasonable suggestions. Do you sense it as a "rolling" vibration/noise, or as a buzzing/rattling noise. Could just be a failed exahust system mount
Alternator IS engine speed related, not road speed. This you can check in 2nd gear, and go up in engine rpm to see if the sound is coming from under the fuel tank, and at what engine speed it starts at. The alternator nose cage bearing could be the source.
Could be in the transmission, but you say it makes the noise regardless of the gear? If it does come from the tranny, when at the speed, pull in the clutch and coast down. If the sound suddenly stops with the clutch pulled in, it unloads the tranny and would unload the bearing at issue.
Wheel bearings are easy to sense, put the bike on the centerstand and rotate the rear wheel. Should be no play up/down, side to side/twisting, should be no "rumbling" feeling or sound. My bike made it to 120k before I replaced the front wheel bearings, and that was more to satisfy myself than any noise I heard. Rear drive hub bearings are still original and quiet at 170k.
One comment regarding the transmission.
The output shaft turns proportional to road speed. It hooks to driveshaft, to final drive, and to wheel. So an output shaft bearing can't be ruled out.
Sorry for the lack of info, fellas. Good point. 3rd owner. 62K miles. I recently put a used transmission in the bike (1500 miles ago). It seems to be working fine. The noise definitely started today on the second half of my ride. I spend a lot of time laying down behind the fairing. I didn't notice it until this afternoon. You can't hear it when you're sitting up.
There's no "feel" to it at all. It's like someone turns on a noise maker at 75 mph. It's the same type noise as the fuel pump, but it's a different pitch.
It's definitely dependent on ground speed as opposed to engine speed. It happens at 75 mph in 2nd gear or 6th gear.
You're scaring me a little bit Paul, but I'm pretty sure it's coming from the front of the bike.
I hadn't tried pulling the clutch in. That's another good thought.
PR2 front tire?
My guess from a thousand miles away based on your symptoms ... Something starts vibrating due to wind speed.
After putting a lot of thought into it, I think Paul has nailed it.
It would seem that you should probably be able to make it come and go by gently coming off and on the throttle,
(ie-very gently applying torque to the shaft, then transitioning to very slight deceleration.) but possibly not.
That is the only thing I can think of that would fit the senerio you describe.
The "wind noise" diagonosis doesn't work in my mind, because the speed at which the noise occurs, would change if you
were riding into a headwind, or running with the wind.
The front tire doesn't really make sense either, as it would go away/change cornering, or changing lanes.
With quite a lot of intrepidation, I tore into mine this summer out of necessity and lack of funds. I had never been inside a transmission before,
but it was really pretty simple and straight forward so I wouldn't let it scare you. I replaced input and output bearings, and the front bearing on the input shaft-it's quiet as a mouse now.
Thanks for the info. I'm starting to think this is much ado about nothing. It was windy yesterday. The noise happened at about 65 mph going into the wind and about 80 mph with the wind. I've managed to convince myself that it is just something rattling around at a specific (wind) speed. I probably should have figured it out quicker, but the "metallicness" of the noise was pretty unnerving. I'll take a look around the front end when I get a chance to see if I can find anything loose. If not, I'll buy some better earplugs.
There ya go! If it gets worse, then you will have a better handle on the problem.