i recently purchased a 2002 cbr 600 f4i with just about 16100 miles and i have lately noticed that when cruising with the tach at around the 5k range there is a slight stumble but when i give it gas it feels as it takes right off and there is not a problem. today though my buddy was following me home and he said when i got on it all he smelt was gas. also i feel when warming up when the engine temp is around 140 ish and i give it slight rev and catch it on its way back down to rev again slightly it will some times sound as it is stumble. i know the plugs are due to be changed but could this be a fuel pressure rugulater problem also?

 

it might b but check your plugs first then do fpr let me know ive got the same issue i changed the plugs went away for a while nd it think its starting to come back

 

FPR needs to be replaced. I had the same problem and it fixed the issue