Here ya go...
http://rapidshare.com/files/49522145/YZF600R-FSM.pdf
Hit the free user button, and go grab a beer, it takes a few minutes to download.
There's a section for diagnosing problems via the Tach, starting on page 60 of Chapter 8.
I didn't read the whole thing, but you might have a bad throttle position sensor.
JC