3- Alinhamento de quadro (não quatro) elástico (rear suspension).
In general terms could be "rear suspension service", but then there is the subsets of this kind of service, for example the servicing of shocks (changing of rear shocks, for example), damping adjustment (here involves the notion of compression and absorbing dampings, etc).
In sum, you could say that you do the "servicing (and reconditioning, if so) of rear suspension."
In time: to those that are newbies in the world of motorbikes (like me), "suspensão traseira" is called (quadro elástico) and "suspensão dianteira" would consist of "bengala e mesas". I have learned.