Spark Plugs, is there a difference?
Ultimate HDF Member
Joined: Dec 2007
Posts: 9,254
Likes: 283
From: Lake City, Florida (Native)
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 ..
Seasoned HDF Member
Joined: Mar 2010
Posts: 38,315
Likes: 6,329
From: Honah Lee
Just my opinion
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.
Last edited by Jackie Paper; Sep 14, 2018 at 10:27 AM.
Road Master
Joined: Jun 2008
Posts: 1,065
Likes: 33
From: Illinois
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Ultimate HDF Member
Joined: Jan 2008
Posts: 6,532
Likes: 132
From: SoCal
No difference except platinum tipped will last longer than std. So I guess there is a difference
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Road Warrior
Joined: May 2010
Posts: 1,348
Likes: 52
From: Central Illinois
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.
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.
