What type of gearbox oil does a Yamaha SR125 motorcycle use?

According to the Haynes Manual for YAMAHA XT & SR125 Singles, 1982-2002

" Use only SAE 20W40SE Engine oil when topping up / changing."

//////////////////////////// That is ok if you live in a hot country or in the desert its too thick for UK you need 10 W 40 dont use full synthetic semi is best or rock oil change every 1,000 -1500 miles for a healthy engine