Radiator cooling capacity is dropping

[bartsscooterservice]

It that case it seems normal and there's nothing to worry about ?

[Stanley]

Since the coolant level was low, maybe check the radiator and all hose connections carefully for leaks. After a few weeks even a tiny leak will bring the coolant level down enough to overheat the engine. Also use coolant recover radiator cap and overflow bottle, Sapporo or otherwise. They also have a one-liter beer can for extreme conditions such as the desert.