Whilst it is – sometimes – possible to open a digit locking mechanism when you’ve forgotten the pin code, it is pretty tough. In many ways that is actually reassuring, since you are buying these locks to help to keep your helmet safe.
That is not much consolation though if you have forgotten your code and can’t open your lock! The short answer is that yes, so long as the lock is open you can change the pin combination. That could be useful if you have a pin that is not as memorable as you thought it might be!
If the lock is closed though it is much harder, and you may have to just cut the lock off and start again with a new one.