They are a "fouling resistant" plug according to NGK part number listing. Looks like some 2-stroke snow mobiles use them in OE applications. Just wondering if any has run them with any luck?

 

Once you go R6725-x or R7420-x you will never run anything else unless you are out of money.

 

+1!!

Interesting observation I have had with plugs - I run BUR7EQ leading and BUR9EQ trailing on the street and R6725-11's all round on the track.
Car sits about 98*C water temp constant on the track with the R6725-11's, but if I use the BUR's on the track, the car will overheat after about 2-3 laps.

I'd use the R6725-11s all the time if they weren't $120 a plug over here!

 

Try getting the Greddy RE11's instead, identical plug to the 7420, just re-badged and (shockingly for Greddy) cheaper. You can get them through RHDJapan for $200 NZD for a pack of 4 shipped: http://www.rhdjapan.com/trust-greddy...tary-13b-13926

 

does these plugs really make that much of a difference? or is it because u r pushing over 450 whp that's when its required?