Stock Harley plugs works as good as any.
The suggested spark plug gap for a 1973 Harley Davidson is 0.040. It is the suggested gap for most of the spark plugs of that era.
The top end of the engine, the part that houses the valves, spark plugs, etc. is called the heads. Harley Davidson designed the outside of their heads resembling a pan, a shovel or a knuckle , so Harley riders nicknamed them accordingly.
Gap the plugs .038" to .043" and torque the plugs to 22 ft/lbs.
I prefer Autolite plugs. Dyno shows them to add about 2 HP.
.040"
The spark plug gap for a 1999 H-D (Harley Davidson) is .032 to .036. The actual gap depends on the brand of spark plugs.
There are two spark plugs on a harley motor. Typically on the left hand side, 1 per cylinder.
If it's points or a Dyna S ignition you set the plugs at 28, other wise you set the plugs between 38 - 40
it has to do with your ignition system. must be t-storm heads off a buell both of which are dual fire ignition systems.
40
The recommended spark plug gap for a 1996 Harley Davidson 883 Sportster is .040. That is the most common gap for most Harley Davidson engines.