If you could get a video that would be helpful.

 

I seem to have a similar issue with my 02. Neutral seems to be fine all the way up to around 8-9k and gets a little intense sounding(as if the engine is gonna blow) then off throttle backfire. Probably sparkplug issue no biggy. Anyways, upon riding at 3500-5500 rpms the bike seems to rumble rather than raspy sound typical bikes/02 zx sounds like. Unusual sound for sure. Poses question that hopefully will be found out tomorrow upon the ignition switch/maintenance. Find out anything else let me know. Ill post again if i fix/find problem.

 

Yeah I'll try get a vid but there's no noise in neutral only in gear and whilst accelerating.. and it seems slightly louder if I was to hang off the left side slightly it definitely seems engine related but I have no idea what it could be! It will be hard to film I may have to get a pal of mine to get me as I'm coming past, anyway I'll try sort a vid to represent the problem sorry Im sounding rather vague but its hard to describe lol

 

Bump. I am still having issues rode 30 miles today doesnt seem to be a problem with power. Just a noise that is alarming to me. Ive seen similar 02 zx6's that sound crisp from 3-5k and all the way through. To me knowing car mechanics it would sound similar if the engine is running on less cylinders. Which i might be able to fix with air flow check in carbs or something like that. Carbs however is a new thing to me electronic fuel management is more common =). Any new info would be greatly appretiated thanks