hi guys a bit of advice please,my gs12 ,o5 plate 13500miles ,has started to run like a loppy dog,took the plugs out ,the left one is perfect colour,but the right one is all sooted up,it struggles to tick over jumping all over the place ,normal riding it seams to hold back a bit ,the exhaust tone just doesnt sound right to like a fluffing ,oh i have checked i have a good spark on all four plugs,whitch leads me to suspect an oxygen sensor on that side ,any advice please.
