The parts of the carburetor that are involved in getting the bike started, have really tiny holes and passage ways. Those holes get clogged up easily, especially if the bike sits for any length of time without running. As they say, the devil is in the details when it comes to cleaning the carburetors. The main jet and the slow jet are really easy to clean. Unfortunately, they have no impact on getting the bike to start. The idle jet, the one you can't remove is the tough one to clean. Also removing the idle mixture screw and cleaning those passage ways has to be done.

I can tell you one thing for sure. If you clean the carburetors properly, I can assure you it will start with no problem.

 

+1

Quite true, which is why a good soaking and compressed air is important. You need to soak and shoot out every hole so you get all of the passages clean, not just the few jets in the bowl.

To CBR900RR1998:

Just to clarify, you said you push your choke "up" to start it, which is confusing as it doesn't go up. Be sure you for sure have the choke engaged when you try to start the bike. Sorry if that sounds obvious, but it happens.