I commute every day, so I usually wear earplugs - might be the reason a friend was the first to notice the sound. I said "no, it always sounds that way." until I rode to a lunch appointment without the ear protection later that day. Hmmm, that must be what he heard...
So there's two things:
1.) a kind of whirring or fluttering type noise
2.) a tapping or knocking
I heard #1 the most and my friend heard #2. But there's also some vibration that I think is new, and I noticed it as an extra buzz in my knees and hands while riding. I'm guessing this is just the tapping making itself felt as well as heard.
Because of the ear plugs, I can't say for sure when the noise started, but it'd have to be within the last week or so, since the vibration in my hands and knees is also recent.
I'd checked the valve clearances recently, so the first thing I did was pull the cam cover off and make sure I hadn't made a bonehead move and there wasn't anything knocking around or grinding up there. Everything looks normal and turns smoothly - shims seated, valves springing, no unusual cam wear or timing chain movement.
Then did some searches about clutches and starter clutches before heading to Harbor Freight to buy a mechanic's stethoscope for a couple of bucks. Well, I don't know what I'm doing with one of those things, but it made it painfully clear that there was both a whir and a tap.
I took a quick video, but forgot to rev the engine, what you get at idle is mostly the tap. I can do another one if the whir is interesting, as that's more audible at higher revs. Sorry about the night-time video and the deplorable lack of cleanliness of my engine - seems like the oil seep has gotten worse than usual lately. Here's the vid link - https://www.youtube.com/watch?v=XhFXdGUx5GY
I don't know if there are ways to narrow this down (like more skilled use of the stethoscope), but I'm thinking of pulling the stator cover first to check the starter clutch and then pulling the clutch cover to peer in there.
So, any tips on what to look for or would you start someplace else? Does anything I've described sound like something else entirely?
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