Hi guys,
I'm new here and this is my first post. I have a burning question (pun intended) about using iridium plugs in a 2006 twin cam 88. I bought and installed brand new NGK Iridium plugs in my engine. I soon noticed carbon coming out of the exhaust with a reduction in performance. I pulled the plugs and noticed they were fouled with a thick layer of fluffy carbon (sorry, I didn't think of taking a pic). The plugs I wanted to replace were the HD copper type. They worked well and there was no noticeable fouling on these plugs so there were no fuel/air ratio or ignition problems that I could see before installing the Iridiums. I just want a superior plug with a gain in performance and longevity. Would anyone know why this happened? has anyone had a similar experience or has anyone installed Iridium plugs in a similar engine without any issues? Oh ya, the bike is an EFI. Thanks for your help.

 

Read the other thread above yours with nearly the same title.
Stock plugs are best for HD. Even the SE plugs have caused some people issues.
Ion sensing ignition system. Or whatever the hell its called.
HD OEM plugs will last longer than your bike.

 

Ya thanks Donk 316,
that's exactly what I did. I soon realized this subject was beaten to death almost as much as the great oil debate. I'm back with the original plugs and no further issues. FWIW, I put Iridium in my honda 750 and it ran great. Apparently they improve HP a bit on a harley according to some guy doing a dyno test on youtube so I thought I'd give it a try.

 

 

I've been running the Iridiums in my '04 for about 8 years with no troubles.

 

Might be a hit or miss thing Put NKG's on my 06' last year and right away started running horrible, be going down the road and it felt like it just cut out for a tenth of a second .Started great though. Pulled them and found one of the towers loose. Cranked on the towers with pliers and next day bad again. Tower loose again. put a little red locktite and still ran bad. Took off put on oem's non-removable towers, still there. Only bought the NGK from what I had read here. Now they are like an elf on the shelf.

 

They are NGK DCPR7EIX Hyper IXtreme Iridium plugs. Cross reference checks out according these guys: http://www.harley-performance.com/harley-spark-plug.html. Even Dennis Kirk sells them as a replacement for the 2006 EFI Softail Deluxe: https://www.denniskirk.com/ngk/iridium-ix-spark-plug-dcpr7eix.pdcpr7eix.prd/DCPR7EIX.sku

 

Do you remember which one's you used? Did you have to change the air/fuel ratio?

 

i run them also. are they fine wire? gap makes a big diff.
ex: i installed a set in my nissan qr2.5 and had issues, i increased the gap by .004 and issues went away. yep, not hd but sorta related subject. do not trust mfg gap out the box and the machine maker only makes a recommendation for AVERAGE service.

 

Yup, fine wire, they are iridium. I just check the gap: .038 right on the lower end of specs. Should I go to the widest 0.043 maybe?