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The bike is a 1987 Ninja 750R. I've got a rattle at low-mid RPM that comes in and out. (Can't tell if it's there at high revs, due to motor/exhaust noise).
It has made this noise most of the time I've owned it (bought it this spring, about 7K miles ago). The bike runs well, extremely smooth.
I just adjusted the valves. A few were on the loose side, so I was hoping that was the problem. Starting it up once the bike was all back together, it idled quieter than I'd ever heard it. It was beautiful. But when I revved it up the rattle was still there, and within a day it was back at idle too. WTF?
The cam chain tensioner is the automatic mechanical type. I may pull it and reset it, though I have to remove the tank & carbs to do that.
I'm also wondering whether maybe the chain guides inside are worn now after 15 years and 40k miles.
Anyway, ideas are most welcome.