2001 SV 650 S 36.000Km - water in the oil/ creamy substance

This is usually caused by improper crank ventilation . Check the small vacuum line that runs into the breather box and follow it back to the engine . There should be a pcv valve there it may be plugged and need to be replaced.If the breather filter is plugged this can also cause poor crank ventilation . Its not likely the head gasket as it would be a more noticeable problem , it would cause the oil to turn to what would look like chocolate milk, you would also notice a performance drop as well as overheating of the engine.