Buy the Champion plugs save some money to buy BEER.

 

Been running the NKG iridium plugs in my 2009 RKC since new. Had them in when the bike had the Stage I upgrade installed at the dealer. Bike was ran on the dyno, and not a single issue. I run NGKs in all my motors. Had a 1997 Arctic Cat ZRT 800 triple snowmobile, and NGKs were the only plugs that never fouled out. Best plugs as far as I am concerned.

 

keithhu:

There needs to be some qualification. Iridium plugs when used in a over square engine with low compression as HD stock engines are and with 87 octane gas will ignite and burn faster and out perform copper plugs. However, do a tune and advance the spark, increase compression, and add a more aggressive cam then copper core plugs are the best plugs for the job.

Power is BTU's and all US gas has 115,000 BTU's and that is with all octanes.

When more fuel (BTU's) is burned more power is made. That is how 87 octane gas can produce more power. The higher the octane the slower the burn and the more deposits in the engine. It has been awhile but I think 1 HP is 5,000 BTU's but I would have to look that up again to be sure.

My dealer has taken my trade ins and commented on how strong they run without any performance tunes. He has even mentioned it to HD exec's.

With all my bikes from 88's, to 110's I get 50 to 52 mpg, no pinging at all and a uptick in performance over stock.

I run 87 octane E-10 and have a very clean combustion chamber, no pinging, great gas mileage ( I ride 30K+ a year so that helps) and spend very little money on performance mods. However I am doing a 120R drag bike that will need copper plugs and 93 Octane. I do play every now and again.

 

Wow, glad I didn't ask who has the best looking wife or girlfriend! :-). Thanks for the input on the plugs! T.