I just picked up a 2004 CBR600RR with 37k miles. Ran great when I bought it. Then it took a dump on me. The fuel pump started making weird noises and the bike would not rev above 7k rpms. I pulled over and I heard a really loud hissing sound from the gas cap. I unlocked it and then "boom" I got gas everywhere. I ran the bike with the gas cap off and there was a constant flow of air bubbles coming from the stem of the pump. Also, the pump makes a much weaker sound. The pump sounds strong in the morning, but after a few hours of riding, the pump sounds like it's struggling to pump. I pulled the pump out of the bike and the whole fuel pump assembly was bent/snapped. Could this be the problem?

 

It sounds to me like you have vapor-lock. Check your breather tubes. Thats going to put strain on any pump, and its something that overnight would go away and then comeback with the engine running.


But, the pump being like that isn't ideal either. Do you have any pics of the tank, inside where the long tubes run up to the cap?