1999 Honda CBr 900rr will not start jus...

Has the bike been sitting for an extended period of time (a year or more)? If so, then the carburetors need to be disassembled and cleaned. Sometimes, if you are lucky, you can drain the stale fuel out of the float bowls and - with fresh gasoline in the tank, it may run. If it hasn't been sitting, perform a complete tune up (valve adjustment, replace spark plugs, change oil and filter, etc.).
If that doesn't do the trick, then there's a more serious problem. One, or more, of the required three things for combustion are missing: Fuel, compression, and spark (at the right time). Make sure there's spark - and it is happening at the right time. Check compression. You need to see at least 140 psi on every cylinder in order for it to run.

hi check the spark plugs if they are a black sotty cover replace them and you should be good to go