Speeding is illegal regardless of what you drive, so I highly doubt you'll find any official documents that say bikes can break the speed limit for safety reasons.
Here's some things you could try to get out of paying the ticket, or maybe get it reduced a little at least. Seeing as he wrote you up for the full 25 over, you don't have to worry about getting a bigger fine if the judge thinks you're a cock.
1. Make sure ALL of the information on the ticket is accurate. Date, time, type of vehicle, vehicle year, color, license number...EVERYTHING. Lots of states have rules where if a ticket is inacurate, it has to be thrown out.
2. Did he get you on radar?? If he did, when you go to court, ask to see the calibration certificate for the radar, the officer's radar operator certificate.
If they don't have the ticket correct, most likely it will get dismissed. If they don't have the calibration and operators certificate, most likely the fine will be reduced. The reason they won't drop it is because MOST cops can tell within a few MPH how fast a vehicle was going. They would probably ammend the ticket to only like 5 over because if the officer saw you speeding, and knew you were, but didn't have the radar stuff with him, the judge will still KNOW that you were speeding, but he has no hard proof then.