Read bunch of stuff on these can't seem to find the right answer, been running Ngk DCPR7EIX in the bike came in it for last 20,xxx decided to change them and now she pings after 5,ooo rpm never did before,has a Thundermax auto on it, Chris Waddell dyno tuned her last yr at Strugis WOW!! definitely worth the monies!!! anyway gaped them .40 thou...any idea's?? going to play with gap a little
Tks Randy

 

Ngk DCPR7EIX is one step hotter than stock plugs. If you are going to run NGK which I like The 8 is suppose to be same as stock and 9 one step cooler. Gap them on .035" also. Make sure not to get any anti seize on the tip as it will cause lots of trouble. If too much on the seating area can cause problems too. Really just need it on threads. Little dab will do you. Haven't tried them but the Harley VRod plugs are 2 steps cooler than the Twin Cam plugs. Colder plug isn't going to hurt you as a too hot will. It may be little harder to start or not idle as smoothly, but not likely. Low fuel pressure can cause this also.

 

Will have to check that out...think something else is prob as the ones I took were same plug ran great til the changing of new one's..tks

 

DCPR8EIX is one step colder than the stock plug which i run in my bike @11.1 compression. the 7EIX is same as stock. I run a gap of .035 also.

 

It really depends on which chart you look at to compare the temp ranges. They do vary. It is likely your 8 is one step colder. I don't understand how he ran for 20000 miles with 7 and no ping then new ones ping. Something going on with that. If he still has the old plugs put them back in and see if it pings. Pinging after 5000 rpms makes me think more in the line of low fuel pressure. Strange things happen some times.

 

I agree with u on that its not a spark plug issue.