Hi, I just bought a 82 goldwing and have been noticing when it is cold and lighly reving the engine it seems to have a knocking sound. I notice this also when I first start to take off. If I start with higher rpm's it seems to be lesser in noise and when the engine is warm it lessens some. Almost feels as if it is no firing all alll cylinders also at low rpms but runs great on the road. any suggetions. is this normal?