I tried a higher gear on my track bike last night, switching from 48/15 to 48/14. A dozen or so laps showed that the gear felt good, so I decided to try some 250mtr standing sprints. What they do, is hold you and as the motor pace goes past, the let you go (they only let you go if the track is clear as you sprint out blind) and you sprint around the outsiide of the motobike and the bikes following. My PB is 17.5 seconds. The first attempt my left calf cramped and I did 18.6 seconds. My Second attempt, I spun the back wheel over a bump and I did 18.3 seconds and then the rain came, so that was the end of that - track closed.
Not really enough data to make a assessment on, but my gut feeling is that I wasn't getting up to speed quickly enough.
I should also note that I do weight lifting before work, approx 13 hours before these sprints, so there is a variation in my performance, based on how stuffed I am on the particular night.
Anyway, what I thinking is that, for whatever reason, I'm accelerating quick enough over the first 50 metres, I need to learn how to get the wheels turning quick enough on a fixed gear.