I have an '03 yzf450 and I just noticed a thin film of oil on the outside of the engine body, it seems to be coming from the head gasket, maybe the cylinder base gasket. I notice no oil in the coolant, nor coolant in the oil. The bike doesn't seem to be running any hotter than normal, either. I was wondering if this is something I need to tend to immediately, or if it can wait till I'm doing something like replacing the valves. Any input would be appreciated.