This doesn’t really make sense to me. Angels and Demons are literally polar opposites of each other. You would think that the differences of their energies would either cancel each other’s out or have some other type of volatile reaction. Yet Jace and Clary, who are Nephilim, who literally have the blood of Raziel running through their veins can just get on this demonic motorcycle with little to no adverse effects.
Spoiler Alert: They crash at the end of the chapter, but it’s not because of their angelic energies. It’s because apparently, the demonic motorcycles can’t work in sunlight.
In the end, the motorcycles and how and when they work just doesn’t make sense. I think the motorcycles could have been pretty cool, but Clare once again didn’t think things through and sure in the hell didn’t consider the details of this little bit of worldbuilding.