The Honda Shadow came with a single cylinder 125 cc engine and a V-Twin 2 cylinder 500, 600, 700, 800, & 1100cc, engine, depending on which model you buy. The single cylinder 125 cc has one spark plug. All the other V-Twin engines have 2 spark plugs.
There are four spark plugs in this bike's engine as it has a four cylinder V.
The Honda Civic has four spark plugs, one for each cylinder.
2 spark plugs per cylinder.
It has 6 spark plugs. One for each cylinder.
This bike has a parallel twin cylinder engine so it has two spark plugs.