I was test riding a cbr250rr today, and I noticed a definite flat spot... basically I was picking up speed steadily in 3rd from about 40k, I gave it full throttle from fairly low revs, and at around 6 grand it lost momentum briefly before accelerating properly in the higher revs. I didn't have a very long ride so I couldn't say for sure whether it was occurring in other gears, it was possibly happening in 2nd as well. according to the dealer who has just trucked the bike in from another dealership, it may have been sitting for awhile because when doing a cold start prior to the test ride, it seemed to take some time to sound like it was running cleanly. I've been trying to read up on flat spots because I don't have much mechanical knowledge especially with bikes... i've picked up a few possibilites: 1. the injection system is a bit dirty and basically needs to be blasted out through cleaning/fanging 2. the fuel has been sitting (will try and confirm whether this is the case or not) for awhile and probably should be drained and replaced if thats the case [on a side note, do you generally run bikes on premium fuel?] 3. tuning may be out 4. potentially bigger mechanical problem? Overall the performance was basically the same as what i've experienced on two other cbr250rr's i've ridden, just this is the first time i've felt one seemingly struggle to accelerate even briefly.