1975
on the left side
camshaft cover
There are two spark plugs on a harley motor. Typically on the left hand side, 1 per cylinder.
Harley Quinin is the side kick of joker in Lego batman
remove left side side cover
Right side of the engine behind the cam cover.
1974
It is located on the RH side Crankshaft Cover.
look at the side of the tires that are on it . There it will tell you the max. psi.
Behind the left side cover.
On the brake side of the bike, it is the round cover on the side towards the front of the engine close to your right foot.