Help With New Noise ...

[Jim Moore]

Hi guys,

 

I noticed a new noise on my 2001 R1100S for the first time today. (3rd owner, 62K miles) 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,

[2SlowDave]

Check exhaust clamps, hose clamps, anything that clamps on. Sometimes the clamp screws have insufficient clearence from things they can vibrate against when conditions permit.

On my GS, the clamp on the exhaust crossover would sometimes contact the sump guard.

[roger 04 rt]

Sounds like something vibrating.

[dirtrider]

Morning Jim

 

It is difficult enough to track down vehicle/chassis noises while sitting on the bike moving along & almost impossible over the internet.

 

You have helped us a lot by your detailed description & observation but it is still a SWAG on our part.

 

Most wheel bearing type noises are more pronounced at lower vehicle speeds, same with gear noises & other drive train influenced noises.

 

Things like speedometer or speedometer cable noises can occur at higher speeds & not at lower speeds.

 

Over the years I have also seen a number of high speed air flow relates noises & some sound like metallic, or growls, hoots, or even rotational.

 

If my bike I would accelerate to well above the noise speed then de-clutch & drop the engine to idle then coast back down through the offending speed. That might shed some light on your issue)

 

If still not identified I would disconnect the speedometer cable at the front wheel & re-ride to see if the noise went away (tape the lower cable to keep the inner cable form sliding out while testing)

 

Next, try taping over the horn (or horns) openings. Especially if you have non OEM horn(s). I have seen a number of horns make some very strange & serious sounding noises at higher speeds as the air flow over them gets them talking.

 

If you have added ANYTHING aftermarket that is in the air flow be sure to tape over or remove those. Even a new windshield or seat.

 

As the winter air gets cooler & denser it can cause air flow related noises to appear that weren’t there in warm summer air.

 

I suppose it could also be a tire wear issue but you would think that would be there at lower speeds & in curves also.

 

If it happens at the same vehicle speed but in different gears, that pretty well eliminates engine buzzes & ground outs & clutch/trans input side things.

 

Might be trans output/ final drive related but again you would think the noise would still be there at lower speeds. (probably wouldn't hurt to drain your final drive & filter the removed oil looking for metal chunks & sparklies)

 

If you just can't find it-- In the past I have tracked down some very specific narrow band vehicle noises with a mechanics stethoscope with a long (very very long) hose on it (no stinger) then tape the open end of the hose in different locations on the bike (NOT facing into the air stream though). Cut the hose end at an angle to reduce air flow influence. It will take a pudding bowl helmet or no helmet to use that setup though.

 

[4wheeldog]

My RT did this for a couple thousand miles before the final drive crown bearing died a horrible death. Do the 9:00 and 3:00 shake, see if you can catch it early.

[ron c]

Jim,

I would suspect something in the front cowl area that vibrates at that speed. DR's idea of going faster then drifting down into the problem area might quiet the motor enough to allow you to localize the noise.

 

Ron

[Jim Moore]

Hi guys,

 

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.

 

Thanks again,

[bmw_rider]

I was going to say try a different helmet.

[flars]

It could be caused by the rider. Try closing your mouth. You can test this by making various shapes with your lips. I prefer the 'OMG I love this bike' shape versus the 'Oh SH--' shape.

 

Merry Christmas to all!