Strange "harmonic" while driving...
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  1. #1
    Senior Member TW_in_BC's Avatar
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    OK, so I've replaced my stator coil, chain and sprockets and got her running again, but a new problem has reared its ugly head. From 30 to 40 mph, I get this awful resounding, resonant noise. Waaa.......waaa......waaa.........waaa. As if both wheels were out of round and since the speed limit is 30 thru town, it's a bit of a pain!

    This does NOT affect my speed and does not appear to affect the engine. At first I thought it might be the chain seating-in, since it's brand new...but I don't recall this noise when I replaced the chain a year ago. The ONLY real difference is the REAR sprocket (47 tooth)...otherwise everything is the same as before I made repairs to the engine. I can't imagine the stator would have anything to do with it.

    This "noise" only seems to appear in 4th gear, between 30 and 40 mph. I cannot reproduce it in any other gear or at any other speed range, and it doesn't seem to be related to the RPM's either.



    Any ideas? This one has me stumped worse than any other problem I've had so far. If need be, I'll gladly go back to the 50 tooth rear...just to rid myself of this racket!
    2008 TW200
    Southwest corner of BC Canada

    YouTube channel: Hidden Content

  2. #2
    Senior Member Turtle Chaser's Avatar
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    Try riding with a different helmet, preferably a shorty (ears exposed). See how it sounds then. Maybe it will be easier to pinpoint. Keep us posted.
    GOD BLESS & RIDE SAFE, TC____________ BC rides: Honda SL100, Honda TL125, Penton125 ISDT, KTM400 ISDT

    now riding '06 TW w/ Jimbo Window, Acerbis bushbusters, ProTaper bars w/risers, Pro Grip 737's, Osram Rally headlamp w/modulator, turn signal beeper, Kenda k270 4.00 x 18,
    triple horns w/relay, big pegs, folding shifter, tuned carb w/drilled slide, 15/50 w/D.I.D. O-ring, RedLine 20w/50, Sterns w/extra padding, extra LED brake light, xt225 brake arm, rear Cycle Racks w/hacked milk crate. Hidden Content

  3. #3
    jvt
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    Senior Member jvt's Avatar
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    you only hear it in high gear and going slow. Try changing or checking your tire air pressure. TW's make lots of road noise from the tires

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  5. #4
    Senior Member wrench-puller's Avatar
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    Hey fellow B.C.er, good to hear from someone close by. I too recently did the rear sprocket change and upgrade to a DID Oring chain, but for me my bike got alot smoother and quieter on the road. How many miles on your TW? and what shape is your front sprocket in? Worn teeth will "hang" onto the chain and make it slap as it comes off each tooth, cause a harmonics though out the bike. Try running different tensions on your chain and see what happens to the noise. Another thing to do is check for loose stuff, like skid plate, fender mounts, racks, etc. Harmonics can make it hard to pin point the sorce of the problem so make small adjustments and moves so you can isolate its sorce. My bike developed a small noise and was rpm related, turned out to be needing a valve set and all is well now. Keep us posted on your progress and what changes you make. With the help of guys on the forum I am sure she will ride smooth once again.
    2009 TW200, Jimbo shield, 47&55T rear with DID chain, Maxxis Ceros Rear, Kendra 270 front, extended swing arm, 1"Risers, Rear rack, Raised front fender, XOG GPS.

  6. #5
    Senior Member TW_in_BC's Avatar
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    Well, this is why it is so puzzling!

    I have changed sprockets and chains before and had no problem...maybe it is this combination of sprockets that is the issue? The front and rear sprockets are BRAND NEW, as is the chain. And while I have heard that the O-ring chains can take a while to "set in" I have not had this problem when I changed it out last time.

    This is more of an engine noise...as if it is surging, although the speed doesn't change. It sounds as though I am revving the engine up and down...a real puzzler!



    She is a 2001 and has just over 32000km.



    I'm going to change back to the 50 tooth rear, and see if the problem goes away, because that is the ONLY difference in the setup.
    2008 TW200
    Southwest corner of BC Canada

    YouTube channel: Hidden Content

  7. #6
    Member TWmonster's Avatar
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    Quote Originally Posted by TW_in_BC View Post
    Well, this is why it is so puzzling!

    I have changed sprockets and chains before and had no problem...maybe it is this combination of sprockets that is the issue? The front and rear sprockets are BRAND NEW, as is the chain. And while I have heard that the O-ring chains can take a while to "set in" I have not had this problem when I changed it out last time.

    This is more of an engine noise...as if it is surging, although the speed doesn't change. It sounds as though I am revving the engine up and down...a real puzzler!



    She is a 2001 and has just over 32000km.



    I'm going to change back to the 50 tooth rear, and see if the problem goes away, because that is the ONLY difference in the setup.
    Last night I adjusted my chain a notch tighter and then on my ride home tonight I notice a similar surging and a slow wah...wah... and it worried me. I noticed it mostly on decel below 30. I tried applying just rear brake to see if it went away and nothing. As I was slowing down I was downshifting and it happened in all gears. Not sure if yours is the same problem but I noticed when I got home that with the bike in neutral and pushing it there is a weird clicking noise coming from the front sprocket/tranny/engine area. Was in a hurry so didnt tear into anything yet. I'm wondering if my front sprocket is loose or worn out. (I have a 47 tooth rear and a stock front with a stock chain on my 2001 with 5700 miles)



    Are you sure you got your front sprocket on right and tight?
    My TW is HUNGRY!



    '01 TW200, WPS Handguards, D2moto Foot Pegs, Jimbo's Cafe Fairing, Tusk Handle Bar Risers, Yamaha Rear Rack, 47 Tooth Rear, 3/16 Fuel Filter, Monsterbolts, Monsterbrace, HJC CL-14 Fuse, HJC ACX1, Cortech GX-AIR, RU Outside Teton Gloves

  8. #7
    Senior Member TW_in_BC's Avatar
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    Hallelujah...It is gone!

    Out of frustration/boredom, I decided to exchange the rear sprocket for the 50 tooth OEM type, while I was replacing the rear brake shoes.

    A quick test-drive confirmed that the surging sound and harmonic is GONE!



    It must be something about the 47 tooth, or the number of links or a combination of all of these that created this noise. Whatever...I'm glad it's gone!



    I guess that sometimes it's better NOT to mess with engineered perfection!
    2008 TW200
    Southwest corner of BC Canada

    YouTube channel: Hidden Content

  9. #8
    Banned qwerty's Avatar
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    I had strange harmonics with a 15/47 sprocket set. I don't woory about such things--totally harmless.




  10. #9
    Senior Member TW_in_BC's Avatar
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    More of an annoyance, but what was worrisome was that it wasn't there before and you know how unnerving it is to get a strange new sound after a MAJOR repair!

    Now that I know who the culprit was, I may even switch back to the 47 tooth some day...but not until I've enjoyed a few quiet miles!
    2008 TW200
    Southwest corner of BC Canada

    YouTube channel: Hidden Content

  11. #10
    Senior Member owtcast's Avatar
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    Were you usiing the same chain with the new 47 tooth sprocket? If so, it was most likely not seating in the valleys of the teeth. A chain and sprockets "mate" with use and is the reason they suggest changing both sprockets with a new chain. You can sometimes ruin new sprockets with an old chain. It's especially easy to do with alloy sprockets.

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