Yamaha SR125 (1997) strange noise

[andy_daytona650]

Hey all

Much to my wife's disgust, I ride her SR125 to work twice a week.

I've noticed recently that as soon as it hits 40mph+ there is a scratching/ratting noise coming from the engine, I think. I can't get it to make the noise in idle/revving it on it's stand.

Performance is not affected. It's due a service July and has done 17600 miles so I'm due to change the oil etc. I normally do the very basic stuff but something just doesn't sound right.

Any suggestions or similar experiences / outcomes?
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BMW 310 GS (2019)

[St George]

I don't know the model, is the chain getting slack and slapping the swinging arm or chain guard. Just a thought ?

[doggone]

https://www.bikechatforums.com/viewtopic.php?t=243768

Possible?

[andy_daytona650]

Cheers guys
Oil level if fine and chain seems to be about right. Very useful link there, will take a look, thanks
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BMW 310 GS (2019)

[andy_daytona650]

For completeness; the noise completely disappeared once the chain and sprockets were changed
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BMW 310 GS (2019)

[Riejufixing]

It is good when people take the trouble to return and post the fix.