Honda FR500 Owner's Manual page 11

Rotary oil level
Place the tiller on level ground and remove the oil level check bolt. The oil
level should be up to the lower edge of the check bolt hole. If the level is
low, add engine oil until it begins to flow out of the hole (see page 8 for
recommended oil).
OIL LEVEL CHECK BOLT
OIL FILLER CAP
10