weird sound coming from my 1978 kz650

Hi,

I recently have been having a weird sound coming from my kz650. I thought it was my brake pads rubbing because the sound started to get worse as I drove it more. I rode down a hill going 50 mph in neutral to see if the sound would continue, but it made no noise until I shifted the bike back into gear. I am wondering if anyone knows what this could be or could give some advice on finding out what it could be?

Tried it with the engine running but out of gear? Chain properly tightened and lubed? Tried coasting with the engine off down a slight hill? Chain guard not rubbing?

not sure what kind of a noise, but you can put it on the center stand and run it in neutral, and you can grab the front brake and kick it into gear, and listen for a noise, just have to be real careful that it dosent slip off the center stand.