Help identify an odd engine noise?

[freelyb]

Hey guys, I've been reading the forums for a few months now since I got my GS but now I'm posting for the first time for, well, not the ideal reason. Love the bike, work on it a good bit (everything aft of the engine, don't mess there yet) but unfortunately just started hearing an odd new noise I think is coming from the engine. Not sure what it could be but thinking maybe the lefthand cylinder is scraping the bore? Here's what happened:

I went to the store, about a 5 minute drive, parked outside and came back 5 minutes later. When I started it up there was a really weird noise that was cyclic (like it was matched with the RPM) and kind of...squeaky? Not really a squeak but definitely high pitched, higher pitched than the video below. I let it run a few minutes and it didn't stop so I carefully rode home. By the time I got to the garage at my place, the pitch had changed and it was as it sounds in the video I'll link to.

I'd really appreciate any help or light you guys could shed! I don't want to take the engine apart if I can at all avoid it, I'm also not sure if there's a garage near my place that would look at it for me. I'm pretty hands-on with the bike but anything with the engine kind of freaks me out for...this exact reason haha. Oh and it's a 2001 GS500 (of course) with everything stock as far as I can tell.

https://youtu.be/NVMcpr1chEs

[J_Walker]

sounds like a valve slap. how many miles on your GS500?

[freelyb]

It's at about 26k. Valve slap... meaning the clearances need adjustment?

[sledge]

Any strange noise that suddenly starts is never good.
Its very difficult to diagnose faults this way 
It doesn't sound like valves to me, its too consistent and is a cyclic whine rather than a tap or clatter.

If I had to guess based on what's in front of me I would say.........spray clutch is sticking or even possibly a very rare onset of goats syndrome*

Does anything change if you pull the clutch in? If so that indicates a gearbox issue.

I would start at the flywheel but easy stuff first, check the plugs are tight and the exhaust gaskets are not blowing.

*If you don't know.......search!