I have a 00 CBR 600 F4. It set in my garage for 1.5 years and I just started riding it again. When I stored it the bike ran great. Now the bike is acting weird. It starts and runs, but it acts like it has a slight hesitation on the throttle. Also when your just cruising at any set speed the rpm fluctuates a little and it sounds horrible. I've put new fuel in it and had the carbs cleaned and put in new plugs but it didn't help. I still haven't changed the air filter, which I know I need to do. I just don't think thats the whole problem. Any help would be greatly appreciated.

 

Seafoam... sounds like you got deposits from old fuel sitting in the lines.

 

I was having the same problem because mine was sitting for almost two years. I had to take it in to have the fuel lines and carbs completely cleaned out and the carbs synchronized. Air restriction can cause a problem i would replace the air filter before anything else