Untill recently I’d never herd the term “fairings” if you have a “faired” bike you have a bike with a fairing, how many do you need?
Yeah - it’s singular not plural if you are referring to an individual bike.
I guess some people refer to the left and right and two separate fairings…
i thought it was like sheep.
one sheep, many sheep
one set of faring, many sets of fairing
You may be right, but they would be fairing pannels that make up part of the fairing. 
This is very true, I agree with your point. But it does break down. A bike with a fairing can be said to be a faired bike. Whereas a man with a sheep…
So, when donning your finest cowhide one-piece do you say you’re putting on your leather? :hehe:
Based on your quote above, if it’s a two-piece, are they leathers only until you zip them together when they then become the singular?
Well, if fairing was one word used for both the singular and plural (like ‘sheep’) you would have -
One fairing, two fairing.
That doesn’t sound right to me.
Forgive me, but your example uses the word ‘set’ to make the word ‘fairing’ a countable noun, while it makes sense, it doesn’t follow the same rule as the word ‘sheep’.
IMO, a single faired bike has fairing, without the ‘s’. The word is not used in the plural to refer to the multiple pieces attached to one bike.
E.g. - My R6 has matte black fairing . (I wish)
If, as NJ points out, it is used to refer to the same pieces attached to plural bikes (or a singular bike), then the ‘s’ is used and the word is then plural.
E.g. - On the summer rideout, our bikes’ fairings glistened in the sunlight .
or
E.g. - I have 2 fairings for my track bike .