There are two types of way you can get a speeding ticket.
The first type is from an automatic camera trap snapping your numberplate,then you are automatically sent a ticket. The rules for this are narrow and strict, and if the legal requirements are not strictly met you do not get sent a ticket of this type, or if you do you may be able to get out of it.
The second type isnot automatic. It involves a police officer taking the view that you have committed an offence, and deciding to summons you. The evidence he relies on for this can be wide, variable, and includes almost anything. If it goes to court, the prosecution tries to persuade the magistrates that it was you, and that you were committing an offence. If you plead not guilty, it is for you to try to persuade the magistrates it was not you, or you were not committing the offence.
A photo of the front of a bike (with no numberplate, obviously) does not result in an automatic ticket of the first type. But it might lead to a ticket of the second type if a policeman tracks down the rider, and believes he has enough evidence to prove the offence and that it was you.
The moral is - if you know there is a camera, don't take the p1$. Keep to the speed limit while you're in the dirty spot, even if the camera can't see your numberplate.