There are four spark plugs in this bike's engine as it has a four cylinder V.
Use for example NGK DPR8EIX-9 or NGK DPR8EA-9 spark plugs.
The voltage on a 1984 Honda Shadow is 12 volt.
The spark plugs are located right under the exhaust manifolds of both sides of the engine. You should just follow the spark plugs wire from the distributer.
63 HP
http://en.allexperts.com/q/Motorcycle-Repair-837/1985-Honda-Shadow-Clutch.htm
in the front of the block.
the ground-wire
1984 v65 sabre plug gap and NGK Spark PLug and heat range
The recommended spark plug, for a 1984. Thunderbird 302, V8 engine, is a champion spark plug. The spark plugs can be purchased at most auto-parts stores.
Sitting on it the right side
The fire. order is 1-2
the spark plugs are screwed into the engine block and the top part of them is covered by a single wire, if you have a four cylinder engine, there will be four spark plugs, the wires will all go from the spark plug to a distributor cap and should pull straight off on each end, if you are replacing the spark plugs make sure not to change any of the wire locations