I can't tell much about motorcycle batteries, but I know that usually lifepo type is used which have 2.5V per cell "discharged" voltage and 2.0V deterioration voltage (your battery have 4 cells). Your 9.63V was far from critical, seems like built-in BMS did it's job quite well. Just charge battery as soon as you can and it will be fine. Long stay at fully discharged state, especially at or below 8V - that is battery killer. One night at 9.63V will not do much harm. Building BMS with higher voltage treshold will be just waste of time and resources. Not worth it.