Rhythmic humming at 120kph

Guys looking for some advice. I have an 07' with 26000kms on it. When I get to 120km's (70mph) per hour I start to hear a significant humming noise coming from the read end area. The frequency of the rhythmic high/low humming is kinda like a wooow woooow. Forgive my description but I can't describe it any other way......lol It only takes place in while I'm in 5th gear in the 120kph region. If I pull the clutch in at that speed it stops immediately. I can't feel any vibration. If I downshift to 4th I can't hear it. SO I'm assuming that it's something it's not tire related. I've had the issue for awhile and I'm starting to avoid the 120kph region while I'm on the highway. Any thoughts would be great.
Dave

If nothing is loose or broken, the likely suspect is a harmonic resonance between the tyre and the engine/gearbox combination..... possibly even just the tyre tread pattern at that speed is causing a sympathetic harmonic resonance......

Does it occur more quietly at say 60kph with the same revs, if not then it is likely tread pattern noise at 120kph versus the engine drive train noise in harmonic resonance....

This would be supported by the noise disappearing when you pull the clutch in changing the engine/drive train frequency.

I have a cupped rear tire that is providing the same effect at the moment between 45 and 60, I lean a little to the right and it stops..........just a thought.

Only occurs at 120...two kph's above and below. The revs are at 4k at that speed. Only happens in 5th at that speed as well....downshift to 4th and nothing. Gotta tell you that it's really annoying. Tires are new....Metz Interact 8's. But the noise was there prior as well. I can try leaning the bike at that speed and see what happens. Appreciate the input.

PFD023 said:

Only occurs at 120...two kph's above and below. The revs are at 4k at that speed. Only happens in 5th at that speed as well....downshift to 4th and nothing. Gotta tell you that it's really annoying. Tires are new....Metz Interact 8's. But the noise was there prior as well. I can try leaning the bike at that speed and see what happens. Appreciate the input.

Click to expand...

Try with the clutch in maybe......isolate the noise?

Clutch in no noise

Ahh.....gotcha. Clutch in mine stays and it didn't start until my tire started this wear pattern

My 07 does that from time to time. Has for a long time.

Not sure what that would be caused by. My 07 has over 124,000 miles on it with no noises like that coming from the bike. Good luck finding the problem.

I wonder if there might be some abnormal wear pattern on the hypoid gear teeth of the final drive unit. Could try changing the fluid in the final drive unit check for any abnormal particles of debris? Is there a chance that the sound is there in 4th but due to increased engine noise maybe drowning it out? Otherwise if it only happens in 5th could be a problem with the 5th gearset in trans...... rare though.

Same here. New tires made the noise disappear.
Details: https://www.st-owners.com/forums/showthread.php?123819-Runnin-with-the-Devil-ST1300-Tires&highlight=

gsforster said:

I wonder if there might be some abnormal wear pattern on the hypoid gear teeth of the final drive unit. Could try changing the fluid in the final drive unit check for any abnormal particles of debris? Is there a chance that the sound is there in 4th but due to increased engine noise maybe drowning it out? Otherwise if it only happens in 5th could be a problem with the 5th gearset in trans...... rare though.

Click to expand...

I've changed the final drive fluid twice since I've had it. Starting to think that maybe it's the Metzeler Z8's I put on it when I first bought it. Did some google searching and there are others who have experienced annoying sounds at highway speeds. I'll change the lean angle while riding at that speed and report back.

PFD023 said:

I've changed the final drive fluid twice since I've had it. Starting to think that maybe it's the Metzeler Z8's I put on it when I first bought it. Did some google searching and there are others who have experienced annoying sounds at highway speeds. I'll change the lean angle while riding at that speed and report back.

Click to expand...

Uncle Larry had a set once and he complained of noise and bad handling from those tires on his VFR, you may want to try another brand of tires and I bet that goes away.

970mike said:

Uncle Larry had a set once and he complained of noise and bad handling from those tires on his VFR, you may want to try another brand of tires and I bet that goes away.

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Thanks....I'll run these for the remainder of the season then change regardless of how they are looking.

Sounds like your exciting the natural frequency of the tire at that RPM. I bet all tires howl, yours howl at a higher amplitude. If it was me, I'd change the tire pressure say to 45 psi and take another run. Not sure if it would help. I run my tires at 45 now to prevent cupping. I believe it works as the last 2 sets of tires never had drastic cupping like my first set had.

My Metz Z8's did the same thing, even when they were new.

John

Email Metzler about it they never heard the Z8 complaint.
Z8's Suck. I had a set on my ST could not get rid on the
humming. Then at 1k I got an alien wrench in the rear new tire
after that best tool ever found!!!!!!!

Kessie said:

Email Metzler about it they never heard the Z8 complaint.
Z8's Suck. I had a set on my ST could not get rid on the
humming. Then at 1k I got an alien wrench in the rear new tire
after that best tool ever found!!!!!!!

Click to expand...

Plan on sending off an email as soon as I get home from vacation. Thanks

I have a Z8 on the rear of my 07 and i get the same noise. Never had it with any other tire.

I totally agree with it being the tires.
I just put on a new set of PR4's and now I have the same issue you are talking about.
I double checked the balance at the STealer and all is good. The tires took a lot of weight to get them balance.
More than I care to see. The bike is silky smooth on the road but I do have a hum not exactly aware of just when it starts/stops though.
Will pay closer attention.
.02
Brian