Manual says B9ES, but "spark plug table" says B8ES.

I have been running a "9" because its colder and because this bike is sensitive to detonation.  Plug looks great, so I am sticking with the 9, but nonetheless curious on correct plug

thanks

Plug fouling is the primary concern.  There is no reason to run a hotter range than is required to keep the plug clean.

If it doesn't foul with a 9 then you are good to go.  An 8 should be perfectly safe as well.  I run a 9 in my 125's.  35 hp and 13000 RPM.  Puts a lot more heat into the plug than the 360 ever will.

"Charts" are not always correct...  but then Yamaha data isn't always either. 

Factory service manual and Tech data sheet says B9ES

thanks Dan, that was my thinking
I think it runs close to or as good as stock gets an the semi-synthetic Lucas burns super clean too
how did you get so much power out of your 125?
 

Its a 2004 KX125. They punch out 35 bone stock.