Motor Brand: Mars is the EValbums search for Mars Motor so you can see what others have done, to me that motor seems like it's about as small as I would dare go with.
Forklifts tend to have a hand full of motors on them, some of the smaller pump motors might be a better fit for a motorcycle, my motorcycle is using a golf cart motor because they are $100 used from golf cart shops, but they have their own issues, like not having a drive shaft that extends out of the motor or a support bearing on the drive end of the motor, some of the fork lift motors have odd issues like that as well so make sure you buy something that you have seen in person, some of them have their way of connecting to the fork lift so the motor can be pulled and serviced more easily.
It's great that you are collecting parts already but things like batteries age over time and degrade if not taken care of, so make sure that you keep them charged up, full of water and I've had a number of people tell me that lead acid batteries do not like sitting on cold floors, so at least setting them up on a sheet of wood or foam is a good idea, I wire my stored batteries all together so they are one big 12v battery (6v in my case) that way I can use a single small trickle charger to keep them all topped off without boiling them.