I just got my first Harley, an 08 Superglide. I’m going to change the plugs next and I wanted to see what some favorite types/brands are.
Any suggestions would be appreciated. I’m looking more for fuel and engine efficiency vs more horsepower if that matters.
Thanks in advance.

 

You can run into problems with the resistance of some aftermarket plugs. Just stick with Harley plugs, they work just fine.

 

Run Harleys. Not sure if yours is different but mine uses the plug resistance to detect ping. The exact look alike NGK called out has a lot more resistance. They seem to run OK in mine but I drive super easy on level sea level ground.

 

Listen to these 2 guys...just the plain ol harley plugs are just fine. I change them once a year but not because they're bad but they get a little discolored and that kinda **** drives me crazy lol.

 

Ok will do. Thanks guys. Ride safe!

 

These......

 

Throw those junk Champion Harley’s in the garbage and get yourself a set of NGK’s.

 

Harley subs out TCs plugs to NGK. Problem is NGK version is designed for Metric Sport bikes and their spec for interference is greater for electronics.

Like I said above, they work but those using sorry fuel and hard on the throttle will probably hear pinging if their exhaust is not too loud.

 

Let me first say that I am not an expert on this particular ignition system, but....

The system works by detecting ion flow through the spark plug gap prior to the ignition event. Ion flow is allowed by the presence in the gap of combustion byproducts caused by preignition. The "resistance" if the spark gap is huge compared to the resistance of the plug and plug wire, to the point where these other components are insignificant to the task of detecting preignition. If this were not the case, the natural increase in the plug gap over time, and the predictable variation in setting the gap in the first place would have a much bigger effect on the system than the properties of the plug.

So, IMNSHO, the requirement to use only Harley Davidson plugs originates from the marketing department.

TMSAISTI!

 

That is not correct. The Harley Davidson 6R12 plug is exactly a Champion RA8HC not an NGK. Put in a pair of NGK DCPR7E and take the gap down to .038 and the bike will run better/smoother.