Spark Plug Material
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Road Captain
Joined: Nov 2018
Posts: 614
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From: Hendeson, NV
Spark Plug Material
I just completed a Stage 1 upgrade and am thinking about changing spark plugs. I will appreciate any feed back on
1. platinum compared to iridium spark plugs,
2. your use of the HD SE standard compression spark plug, (It seems HD likes this spark plug after an stage upgrade.)
3. your gap setting. (The service manual calls for a .038 to .043 gap, but the SE plugs come with a .035 gap; I am curious about where in the range specified in the service manual to set new plugs.)
Thanks.
1. platinum compared to iridium spark plugs,
2. your use of the HD SE standard compression spark plug, (It seems HD likes this spark plug after an stage upgrade.)
3. your gap setting. (The service manual calls for a .038 to .043 gap, but the SE plugs come with a .035 gap; I am curious about where in the range specified in the service manual to set new plugs.)
Thanks.
Seasoned HDF Member
Joined: Jul 2008
Posts: 9,282
Likes: 1,139
From: southeast PA
Use of anything other than the stock plugs is of questionable benefit. If it makes you feel better and you want to get more expensive plugs then go ahead, but you won't see any real world advantages.
Road Master
Joined: Nov 2015
Posts: 1,240
Likes: 395
From: georgia
And there might be disadvantages. The ion sensing is based on stock plugs.
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,074
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the truth is that most any plug can be used, they even have multi-strike ion systems. all the plug does is ignite the mixture which basically any plug can do. the magic of ion sense is that the ESTABLISHED flame kernal can conduct an electrical current and it is this current that is measured and interpreted for various functions.
Ultimate HDF Member
Joined: Jul 2014
Posts: 8,251
Likes: 3,990
From: Windwardside, Saba N.A.
If your ride is to the level that spark plugs make a difference, you are ahead of 99.99% of owners.
That said, for exotic spark plug electrode material, Ruthenium > Iridium > double Platinum > single Platinum.
Champion-made resistor spark plugs use 20K Ohm resistance, virtually every other maker uses 4K Ohm. Harley spark plugs are made by Champion. If you want Ruthenium plugs your source will be NGK (they are expensive and sometimes available only from Japan).
For street Harleys, 0.044" gap seems to work best for me. If you build a truly high-compression engine, a smaller gap might work better.
YMMV
ETA: There was a time last year that I bought ALL the Harley double-Platinum VROD spark plugs that were on eBay. They were "obsoleted" by Harley and I like them. I now have several years supply, maybe a lifetime.
That said, for exotic spark plug electrode material, Ruthenium > Iridium > double Platinum > single Platinum.
Champion-made resistor spark plugs use 20K Ohm resistance, virtually every other maker uses 4K Ohm. Harley spark plugs are made by Champion. If you want Ruthenium plugs your source will be NGK (they are expensive and sometimes available only from Japan).
For street Harleys, 0.044" gap seems to work best for me. If you build a truly high-compression engine, a smaller gap might work better.
YMMV
ETA: There was a time last year that I bought ALL the Harley double-Platinum VROD spark plugs that were on eBay. They were "obsoleted" by Harley and I like them. I now have several years supply, maybe a lifetime.
Last edited by Sierra977; Feb 16, 2019 at 09:55 AM.
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Road Captain
Joined: Nov 2018
Posts: 614
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From: Hendeson, NV
I have a 2017 1200 Sportster. The HD Service Manual lists the range of spark plug gap at 0.038 to 0.043. The SE spark plug for the 2017 Sportsters comes pre-gapped at 0.0325. I just completed a Stage 1 upgrade that didn't include an change to the compression of the engine.
I am still trying to get answers as to
1> Why the range of gap specifications in the Service Manual,
2> What factors should be considered in choosing where in the range to gap the plugs, and
3> Does the gap requirement change if you use SE plugs after a Stage one upgrade?
All information and ideas will be greatly appreciated.
I am still trying to get answers as to
1> Why the range of gap specifications in the Service Manual,
2> What factors should be considered in choosing where in the range to gap the plugs, and
3> Does the gap requirement change if you use SE plugs after a Stage one upgrade?
All information and ideas will be greatly appreciated.
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Seasoned HDF Member
Joined: Jul 2008
Posts: 9,282
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From: southeast PA
1. There is a range because .0005 gap will make no difference with your setup. You can try gapping them at both extremes, go for a couple of long rides and see if you can tell any change.
2. The factors that come into play are usually when you have a built, hi comp motor. You don't, so no worries.
3. Use the gap as recommended by the plug maker.
You are over thinking this. As long as you're going down this road you might want to index each plug. It might help more than a couple thousands in a gap.
http://www.nightrider.com/biketech/h...s_indexing.htm
2. The factors that come into play are usually when you have a built, hi comp motor. You don't, so no worries.
3. Use the gap as recommended by the plug maker.
You are over thinking this. As long as you're going down this road you might want to index each plug. It might help more than a couple thousands in a gap.
http://www.nightrider.com/biketech/h...s_indexing.htm
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