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Thread: Strange sound during idle?

  1. #1
    Senior Member jannaruto's Avatar
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    Strange sound during idle?

    Hello Guys,

    Can You check this short recording and try to help me what is that strange "noise" at some points?
    The idling is like thump thump thump thump, very regular but a couple of times in these 10 seconds there is a sound like: thump thump thump thu thump thump thump thu
    Attached Files Attached Files

  2. #2
    Senior Member phelonius's Avatar
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    The the is your TW telling you it is almost missing a beat.
    Phelonius

  3. #3
    Senior Member jannaruto's Avatar
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    Quote Originally Posted by phelonius View Post
    The the is your TW telling you it is almost missing a beat.
    OK, what can cause that? Lean condition in example? Or too much fuel instead? How do I solve?

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  5. #4
    Super Moderator Purple's Avatar
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    Ear plugs …..

    The TW runs a “wasted spark” – eg every time the crank comes up to TDC you get a spark, even on the exhaust stroke

    The inlet valve “should” block fuel flow to the cylinder at the appropriate exhaust stroke, but if even a little is getting through it would explain the noise you’re hearing. Now, I may be talking out of my own personal exhaust pipe here, but the first thing I’d do in your circumstances is double check the inlet and exhaust valve settings.

    If your valves are set correctly, there shouldn’t be anything getting through at the wrong moment, so it’s unlikely to be your carb jet settings.

    The only other thing that “could” be upsetting your valves are the seating arrangements – but as that involves a full top end tear down, if it ‘aint broke, don’t fix it – just keep an eye on it and get a set of ear plugs …….

    (If you put your year of TW and the mileadge in your sig line, it’ll help to diagnose things like this)
    Bobo413, Poppasmurf and admiral like this.
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  6. #5
    Senior Member jannaruto's Avatar
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    Quote Originally Posted by Purple View Post
    Ear plugs …..

    The TW runs a “wasted spark” – eg every time the crank comes up to TDC you get a spark, even on the exhaust stroke

    The inlet valve “should” block fuel flow to the cylinder at the appropriate exhaust stroke, but if even a little is getting through it would explain the noise you’re hearing. Now, I may be talking out of my own personal exhaust pipe here, but the first thing I’d do in your circumstances is double check the inlet and exhaust valve settings.

    If your valves are set correctly, there shouldn’t be anything getting through at the wrong moment, so it’s unlikely to be your carb jet settings.

    The only other thing that “could” be upsetting your valves are the seating arrangements – but as that involves a full top end tear down, if it ‘aint broke, don’t fix it – just keep an eye on it and get a set of ear plugs …….

    (If you put your year of TW and the mileadge in your sig line, it’ll help to diagnose things like this)
    Tw200
    1993
    52984km

    What I have to touch to fix?
    Is something I can fix modifing the idle screw or the mixture screw at bottom of carby?

  7. #6
    Super Moderator Purple's Avatar
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    First things first - check your valve clearances ……

    https://tw200forum.com/forum/technica...r-manuals.html
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  8. #7
    Senior Member jannaruto's Avatar
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    Quote Originally Posted by Purple View Post
    First things first - check your valve clearances ……

    https://tw200forum.com/forum/technica...r-manuals.html
    Here me back, that seems fine tho
    What could it be then

    Also I want to mention that ear plugs are not necessary, the audio file is kinda loud because I put the microphone basically almost touching the engine, but it is absolutelyt a regular engine sound ^^
    I just would like to solve that "missing beat"
    Last edited by jannaruto; 07-20-2017 at 05:53 AM.

  9. #8
    Senior Member jannaruto's Avatar
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    Quote Originally Posted by AGman View Post
    Nearly 53000km huh? Are you the only owner? Had any work done to the engine recently?
    Nono I am not the first owner, its an used bike, I purchased like 3 months ago
    I never noticed before because You know there were other things to do like install a brake disc, fix the electric circuit (because the front light was intermittent) etc so I didn't really paid any attention to it
    But after three months of daily riding You start to get "a feeling" for the bike so You start to notice very small details that You never noticed before
    So probably this was there since I purchased the bike

    No recent engine work, as far as I know it was never touched

  10. #9
    Senior Member admiral's Avatar
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    I've listened to your audio file numerous times. What I'm hearing can best be described as "the engine is skipping a beat".

    I'm with purple in that you may want to verify the valves are set within specifications.

    If they are: You can actually perform the below in any order I just put them in this order but not a requirement.

    First, increase your idle speed and see if this "skipped beat" or "thumping in your words" goes away at the higher idle setting.

    Second, decrease your idle speed and see if the mentioned sounds become more pronounced or disappear.


    I'm not engine nor engine tuning expert, not even close but my thought is this sound should, could, most-likely will decrease or disappear when the engine idle speed is increased. You suggest or are asking if the pilot screw adjustment is needed. If you know how to adjust the pilot screw, you could make slight adjustments in or out with the screw and see if this makes a difference in the sound. Should you do this, you may want to make sure your engine isn't running too lean (white ish color or too rich (black sooty). Heck, you might want to check the condition of your spark plug now to see if it's adjusted correctly and not dirty or worn.

    This next week I'm going to listen to my TW engines and see if they make a similar sound as yours does. I'm not probably giving you the real help you need but thinking (writing) out-loud to try and give you some ideas.

    Keep us posted. Thanks.
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