Probably your cam chain tensioners, or possibly the roller finger followers (lifters for overhead cams). No big deal unless the tapping is very loud. Just be sure to keep clean oil in the bike, and change at a max. interval of 1500 miles.
My F2 does that. I've replaced the cam chain tensioner and it still does so there are other things that cause it. I've been told by people I trust though, that if it does go away after the bike warms up don't worry about it too much. Just keep an eye on it and if it gets worse then get it checked out.
Got that in mine. When I start it, you can hear a kinda rattle that's pretty loud. Goes away once you ride a few blocks. If you stop even for a minute and shut off bike, it comes back. Hasn't gotten better/worse over time and 6000km so I'm not too worried. I did replace my CCT, didn't fix it at all.
is it a cbr1000? i have the 88 model, it rattled when i bought it in 90, changed the cct, and it still rattles today until it warms up. a friend has changed his with the newest release (there have been many) and his rattle is now gone... i dont think it really bothers anything, since the last time i adjusted the valves there was no sign of wear.