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Nightfly
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4,042 Posts
Discussion Starter #1
A couple weeks ago a guy who sold his Sportster gave me a set of (new) Screaming Eagle Spark plugs to try. I had recently installed an adjustable ECM, with RPM redline set at 6500. New Crane Cam coils and a few other mods. Before installing SE plugs the bike pulled strong and went right to 6500 no problem. Put the SE plugs in and I could not get it over 6000, sometimes barely over 5500. It would just nose dive at that point. After slowing down to about 3000 rpm the bike would kick back in.

After checking all the electronics and finding everything working as it should, I decided to change the plugs out and put in a fresh set of NGK. What a difference. Engine seemed to pull stronger than ever and goes right to 6500 rpm no problem.

I read on other forums that no one had a problem with the SE plugs. But those were all in touring bikes and not much for the higher rpm. I could cruise all day at lower RPM but winding it out is where the problem seemed to be.

I'm not pushing NGK or any other brand of spark plugs, I'm sure everyone has their brand of preference. NGK is what the shop closest to me had in stock.
 

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ZAMM Fanatic
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2,730 Posts
If you don't mind my asking, did you set/check the gap on the SE plugs prior to installation?

Did the new coils come with any recommendation on changing that gap, based on the higher output of those coils? If so, did you re-set the timing afterwards?

Did the instructions that came with your new coils make any mention of using a ballast resistor?

I installed a big fat yellow coil on an old Subaru I owned without properly wiring in a ballast resistor and within 1000 miles 80% of the electrodes on the plugs had been vaporized. Gone..

That coil would put out a blue spark well over an inch long running on full 13.8 without a ballast.
 

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Female Rider
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9,324 Posts
Yep, my bike rebels at anything other than NGK too. Gaps were set correctly. She just kept stalling out. Put the old ones back in and she hums beautiful songs.
 

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Nightfly
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4,042 Posts
Discussion Starter #6
Part number 32192-10 That part number seems to be recommended for a wide range of Harley's. I wonder about the heat range. They were pretty black when I pulled them out. Considering I was "trying" to hammer it at the end, that's not a good sign.
 

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Gone.
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17,871 Posts
That's the right number for a Sportster SE plug. Maybe there was something wrong with one of the plugs? Cracked insulator maybe?

Harley plugs, SE plugs, Autolite, NGK, and Champion all seem to work about equally as well from what I've seen. One might resist fouling longer then another, but I've never noticed any performance difference.
 

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Registered
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4,169 Posts
I have had great luck over the years using NGK plugs. For me it has nothing to do with performance but I like a plug I can just install and then forget it. The NGKs do that for me.
 

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Pegasus trapped in a human body on a motorcycle
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9,225 Posts
I ran NGK plugs in my Shadow, and they did excellent. That is what is in my Yammie as well. Outstanding plugs.
I am considering moving to Iridium plugs, if I end up goin with an aftermarket ignition. I believe NGK has them.
 

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Nightfly
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4,042 Posts
Discussion Starter #11
That's the right number for a Sportster SE plug. Maybe there was something wrong with one of the plugs? Cracked insulator maybe?

Harley plugs, SE plugs, Autolite, NGK, and Champion all seem to work about equally as well from what I've seen. One might resist fouling longer then another, but I've never noticed any performance difference.
Today I put about 60 hard miles on the bike. After a couple high rpm quarter mile runs, I pulled the plugs and both had a light tan - gray color. Engine never missed a beat. Can't say if the SE plugs had a crack as they were quickly deposited in the nearest dumpster.

I agree with you Eye, most plugs have never given me a problem. This is the first time any plug has actually caused my engine to cut out. In my drag racing days I've tried all brands, usually switching around because of the heat range needed and other variables. Never felt a performance difference either. They either fired or they did not.

I know most guys swear by "their" brand but I've never had one in particular that I thought was better. Whatever works, right now it's NGK. In the future I'll be a bit suspicious of SE plugs.
 
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