I've been following the thread about the spark plug choice for a C5. And it got me curious about what is in my 2011 B5, so I pulled it out tonight to check the condition. I was expecting a Bosch WR7 from reading the other posts. Surprised, it is an NGK B5ES. The bike was purchased from a dealer, new in April 2012.
The spark plugs for UCE bikes have been discussed, tested and written about several times in great lengths.
NGK 5ES has two aspects that are not in harmony with the OEM Bosch spark plugs. First, it is non-projected (Bosch is) and secondly 5 is a tad too hot.
How did it get there ? The very likely reason is that dealer put it there. Why this plug ? The older iron barrel (older REs) had non-projected spark plugs so he picked the same feature. Why 5 heat range ? In the very very early days of UCE introduction in US, it was assumed that the Bosch OEM plug was equivalent to that.
The bike will run on all kinds of plugs in heat range of 5 to 8. It will also keep running whether projected or non-projected plug is used. It will also run whether it has resistance or not. You may not see their effects in a short time but in the long run they can affect the longevity of engine, and other performance.
The closest to OEM in all aspects including heat range, depth of spark in chamber and resistance is NGK BPR6ES. The link below has a comparison of different types of plugs.
http://www.enfieldmotorcycles.com/forum/index.php/topic,10553.0/all.html