just found this cross reference table and thought i would post it for those that might want to change brands of plugs.

http://www.harley-performance.com/ha...park-plug.html
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Great reference chart. Thanks...

 

web link for cross reference.

select power sport not automotive then follow the drop down selections

http://www.sparkplugs.com/

 

I run Champion RN12Yc in my 93 Tour Glide. Tried the HD 5R6A as recommended in the manual they fouled out the 1st day put the Champs back in and have had no problem. They appear to be the same size ceramic which would indicate the same heat range. might try the BPR5ES-11 to see how they do.

 

investigate "ion" before switching away from H-D plugs....
It can affect the way your ECM operates based on an 80 volt DC charge the ECM sends down the plug wire between cylinder firings measuring combustion by way of ION content and resistance to ground.

There is a bunch of information regarding this searching this forum....Take the time to read them.

 

I have used stock and one step colder heat range NGK, Autolite and Champion in 03 and 07 HDs.
Absoluteley no issues with any of them. Take a look at the standard HD plug and compare it to
a Champion. They are the same.

 

IIRC that is only on bikes made after 2005. That said on my 03' I use the NGK Iridium plug in one heat range hotter than stock. I have not checked the since I have had the SERT install, but judging from what they looked like before the install, they should be just right, as they were a bit reading a bit lean to start with.
On my 08' FLHX I will stick with the HD branded plugs basically because of the reason stated above. I may switch out to another brand in the future.....only time will tell.

 

I compared the RN12Ycand the HD 5R6A side by side up side down inside out measured checked and scoped. found no difference in them at all. Don't know why it will not run on the HD plug.