HD, no real reason to go different - unless you're racing the bike.

 

What plugs are you using and are they all created equal?

 

I use the HD gold ones and seem to work well. Change them every spring(~12k miles). I know others that use Autolites and they work well too.

 

Any plug made for the Application and proper Gap will work I like NGK Iridiums, overkill am sure but starts a tad quicker with them probably not enough to matter but love just touching the button and fires right up without a seconds hestation.. I get them at a pretty good discount from the Indy ..

 

Just my opinion. Type of plug has little difference on performance on engine that you could measure. I find it interesting that my service manual says no substitution which is referring to heat ranges and not the fact that you cannot use another plug other then one with Harley's name on it. I use an NKG not that it's any cheaper since Harley's plug which appears to be one thing they sale at a fair completive price but that's it available closer to home. Also it has to be who make Harley's Softail plug since other then not having Harley on it it is identical. I have see were other's say Champion makes Harley's plug but I am a machinist and I know they are identical in all details.

 

What NGK Iridium # are you Guys using? Thanks, Mike

 

Bosch Platinum in my last 6-7 bikes (Shovels, Evos and TCs).

 

No difference except platinum tipped will last longer than std. So I guess there is a difference

 

A plug might be a plug but I used some NGK's on my 2010 Ultra and using the TTS data recording was stunned by all the knock retard. Switched them out with the stock HD plugs and the spark retard disappeared.

Bike ran fine with the NGK's but the ECM was removing up to 8 degrees of timing. I don't think there was any real knock issue but the electronics obviously need to have exact resistance to work properly. If I were to use the NGK's again I'd likely turn the fast knock retard off.

 

I sold parts at an HD Dealer and unless you build a full race motor the standard HD plug and wires are recommended.