I don't want this to become another spark plug debate thread, but I had a strange experience on my 07 SB this week. I was running Screamin' Eagle plugs and decided to swap in some NGK iridiums. The bike started fine, but then, while in traffic, I went to take off from a stop and it almost stalled right out of idle. Later, although running great, I throttled it hard in 1st off a stop and after revving out a but, suddenly, it cuts out! I let off an it came back. I swapped back to the SE plugs and have tried to reproduce the problem, but nothing, it seems to run fine.

Any ideas? hard to believe different plugs would have that kind of effect.

 

I'm not sure what the system is called(maybe the anti knock or something like that), but I've heard if you run plugs other than Harley plugs it can mess with the way the bike runs. I've been told by HD mechanics and people/companies that are big into racing and stuff like that that the best plugs to run in a Harley is Harley plugs.

 

I wonder if the plug gap was too close.
I run HD plugs only, never a problem.

 

I have had issues with fancy brand name plugs in my jet skis, and always just had great luck with NGK standard plugs. So in my Harley I only run the cheapo Harley plugs, not even the Screamin Eagle ones. They run great for me.

 

I've been running the NGK iridiums for 4 years in the SB and around 15k miles and I've never had any issues. The anti knock thing doesn't matter. The resistance of a stadard plug and the iridiums are the same. The only difference is the electrode. I tried to go back to the stock plugs just out of curiosity and after a week the iridiums went right back in. I stalled the bike like 3 times because the throttle response was slow with the stock plugs. The cold starts (first start of the day) the bike would cough and spit. Once I got a few miles down the road and the stock plugs were warmed up the bike ran a lot better. The biggest difference for me with iridiums were the cold starts.

As said above I would make sure the gap is right. Make sure the boot is full seated and make sure the cap the plugs snap onto are tight. I won't go back to stock plugs. Stay away from E3's. I had one implode in my car. Maybe you just got a bad set.

I've ran iriduims for 13 years from cars, trucks, jets skies and my R6. Never had a problem with NGK's or Denso's.

 

Harley Screamin Eagle plugs are made by Champion, NGK plugs are a better plug. Check the gap.