Honda CRF50F Owner's Manual page 71

Other viscosities shown in the following chart
may be used when the average temperature in
your riding area is within the indicated range.
JASO T 903 standard
The JASO T 903 standard is an index for
engine oils for 4-stroke motorcycle engines.
There are two classes: MA and MB.
Oil conforming to the standard is labeled on the
oil container. For example, the following label
shows the MA classification.
(1) oil code
(2) oil classification
Servicing Your Honda
Engine Oil
(1)
(2)
63