i've just bumped into an old friend , and he has started using bosch plugs in his wrf 400 , because the ngk were breaking down after a couple of weeks, he tells me that bosch have no problems and are ultra reliable....and i remember about 10 years ago when i was a bike mechanic that 1 out of 5 NGK plugs we fitted to bikes were duff especially on two stroke machines. it could be our weather though, apparantly if the spark plug packet (box) gets damp then the moisture travels up the electrode in the plug and then you have a duff plug,this is why they stopped putting that miniature cardboard tube around the thread on a new plug because of moisture absorbtion.
