Which kind of plastic material would be suitable for a clutch cover on a motorcycle transition? I'm going to have an online machine shop build a part for me using a CAD drawing that I specify.

Typically, these parts are made of aluminium, but this manufacturer also mills parts out of these plastic materials:


Polypropylene (PP)
Polystyrene (PS)
High impact polystyrene (HIPS)
Acrylonitrile butadiene styrene (ABS)
Polyethylene terephthalate (PET)
Polyester (PES)
Polyamides (PA) (Nylons)
Poly(vinyl chloride) (PVC)
Polyurethanes (PU)
Polycarbonate (PC)
Polyethylene (PE)


Polypropylene, I know, is the plastic used in water bottles, so I know that is not what I want.

This fabricated part will be used for the clutch cover on a motorcycle transmission and will have a raised section that needs to be tapped to allow attaching a gear shifter to, like in the aluminium version below.



I'd like something rigid and strong. Plexiglass comes to mind, but there could be a better alternative that I am unaware of, as long as I am not getting into something exotic that would cost more than aluminium.

Could suggest a good plastic for me, which would need to be oil resistant and withstand typical engine transmission temperatures.
Most plastics consist of linear molecules with little inter-molecular interactions, so most plastics melts too easy. The only ones you mentioned having a chance are polyuretanes and polyamides. They have (CO)(NH) fragments, that forms strong intermolecular hydrogen bonds. So, they are ones of the strongest polymeric materials 

And I will recommend aluminum anyway as it is much harder to screw things with aluminum.