2004 T100 Bonneville A Whine

Discussion in 'Bonneville' started by PlanterJohn, Nov 22, 2025 at 12:54 PM.

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  1. PlanterJohn

    PlanterJohn New Member
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    Nov 5, 2025
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    #1 PlanterJohn, Nov 22, 2025 at 12:54 PM
    My Bonnie has done 25k miles but now it is whining, but not a scream, eminating from under the fuel tank. The noise starts at around 50mph/80kph in 5th gear. It continues even if I slow and change down, then stops after a slow manoeuvre but starts again as I speed up. Any suggestions or do I just run it till it fails and then repair?
     
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  2. joe mc donald

    joe mc donald Joe
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    Dec 26, 2014
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    #2 joe mc donald, Nov 24, 2025 at 12:50 PM
    @PlanterJohn Welcome to the family. The bike may just be cam chain adjusting and needs to settle check the adjuster is not sticking. Do tap the upload a file button and show us all the bike.
     
  3. Robbi18

    Robbi18 Member

    Jun 15, 2025
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    #3 Robbi18, Nov 25, 2025 at 5:25 AM
    That whine is likely your cam chain tensioner. It's a common issue on those Bonnies. The automatic tensioner wears out and doesn't keep the chain tight.

    Don't just run it. If it jumps time, you're looking at bent valves and a massive repair bill. Get it checked out sooner rather than later. A manual tensioner is a popular fix.
     
  4. PlanterJohn

    PlanterJohn New Member
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    #4 PlanterJohn, Nov 25, 2025 at 12:32 PM
    Thanks for your helpful comments Joe and Robbi. I will put your suggestions to the test over the winter with further investigations and rectification - the ultimate aim for this bike is to affix a sidecar in preparation for the time when I no longer feel safe on two wheels! In the meantime I have a 97 Triumph Adventure and a Zero SR/S to play around on.
     
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