The last few days i have noticed a rattling sound coming from the engine, generally only when the engine is up in the rev range (8000rpm+). Ive never known what pining sounds like before, but i think the rattling is pining. I always put BP premium in my bike, however I have only noticed rattling sound on this tank of fuel. Also, I read somewehere that in some cases, using high octane fuel in bikes like gpx's can sometime cause pining and make the bike run rich? Anyone know if this is true? Im considering filling up with standard unleaded for a few tanks to see how it runs. Any advice would be great thanks.