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Discussion Starter · #1 · (Edited)
I have read through a lot of posts on here about spark plug indexing, but haven’t seen a picture showing the optimum direction of where the side electrode opening should be pointed viewed from outside of the head. I have the Screamin’ Squeegle Plugs and will be changing to because that’s what I run. Not going to say which one, as this will start another spark plug post, then it will go in a downward spiral, to “Hell in a Handbasket”, turning into an oil topic.

So I am asking for pictures from outside of the cylinder head, where the opening or of the side electrode should be.

I have read that getting a box of 4 is recommended, as the thread differences will not have the side electrode in the same place. Loosening the plug to the correct direction is obviously not an option.

Removed mine, marked where the opening is pointing, and I assume it is opening to the outside of the combustion chamber.
A little over 1000 miles on these plugs, including 2 trips to the Dynoand on the Dyno in those miles.

H-D Part Number:

Handwriting Blue Product Black Azure


Front and installed opening location:

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Not front (rear) and location:

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Not heard of that, but there is spark plugs you can get with two or three electrodes which actually don't cover the tip just the sides, think the reviews were crap though!
 

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Discussion Starter · #3 ·
Thank you HH but I’m staying with iridium.
 
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Corey did you check this thread:


It has some good information regarding which direction the electrode should be pointed as well as using various thickness of shimming washers to make that happen.

Cheers!
 

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Discussion Starter · #5 ·
Gene. That is one of them that I read through. Yes good information indeed. When my Iridium Plugs arrive I’ll check them like I have my current plugs.
 
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Hang on though- if the intention of indexing plugs is to gain a little better combustion efficiency by having the open face of the plug gap optimully exposed to the intake valve & thus the incoming charge of air/fuel mix, wouldn't spark timing be slightly advanced relative to TDC of the piston crown by shimming the plug position, thus bringing the electrode gap a little deeper into tne combustion chamber? Thus worsening (very slightly) any tendency to pre ignition?

Inquiring minds etc...

J.
And btw, I just installed a new set of NGK Iridiums last week. I got 50,000 km (~30,000 miles) out of them, instead of the 100,000 km claimed. But even 50,000 km is 10 years riding pretty much every day for me. I'm happy with that. Especially as they were $32.50 AUD (~ $22 USD) each, versus $25 back in 2012.
 

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Discussion Starter · #7 ·
I just actually want to have the opening towards the combustion chamber in instead it’s against or facing the cylinder wall in my pictures above, if I am correct.
 

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It doesn't matter.

I've done it and dyno'd. You won't see a power change.

If you are splitting thousandths in the quarter mile, and you optimize timing with the indexing, you might pick up a thousandth in the quarter. But on the street, you won't see any difference.
 
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Discussion Starter · #10 ·
It would be nice to know where the opening is facing. I’ll try the 4 new plugs due in Thursday.
 

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It would be nice to know where the opening is facing. I’ll try the 4 new plugs due in Thursday.
Mark the plug where the open end of the electrode is, and when it is torqued in, you will know where it is facing. Bob's your uncle! Easy peasy............
 

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Discussion Starter · #12 ·
That is what I did on the above pictures.
 
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and you can of course buy indexing washers.

But, again, this is pointless on the street.
 
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Discussion Starter · #14 ·

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Good thread! I think there is still one unanswered question though - the optimum direction the plug should be facing in the combustion chamber (if one were to go through the trouble of indexing). From the outside, standing on the left side of the bike and facing the engine - should the ground strap be at 6:00 relative to the kickstand side of the bike? (so the open end of the plug is facing 12:00 to the exhaust-pipe side?
 

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Discussion Starter · #17 · (Edited)
New NGK Iridium Plugs, gapped to .8mm installed. Pictures showing where the opening of the gap located.

Font Bullet Gun accessory Auto part Cylinder


Only test installed 2 of the 4, because I have to work today. Both lined up the same direction. Leaving them there. The Screamin Eagle Plugs were gapped at .9mm.

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Discussion Starter · #19 · (Edited)
When I got the bike I changed the spark plugs and spark plug wires to Screamin Eagle right away. I’ve run those for about 1000 miles and because I’ve always run iridium in everything, I just changed the plugs. Been running them for the past two days. I really can’t tell the difference.
 
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