don't rev your bike hard the mechanic had pour 1l oil in your bike due to that the bike is not rev smoothly and not achieving the speed it should I would again say drain the oil as it is a desi totka of mechanic to pour oil in clucth plates to let them settle in their place rev your bike with more oil than limit will put pressure on engine seals and you may end up it engine leaking oil from every where rest it your bike and your choice