The engine cylinder head cover nut has a torque of between 7 to 9 foot-pounds. This measurement specification also applies for the '80, '81, and '82 Z50R builds.
well monkeys use to ride thease little pit bike back in the 80s thay rode these littlle honda z50 i own a honda z50r really good little bike
SAE 10w30 any major brand. I highly recommend you use Synthetic oil in any air cooled engine.
It may stall out.
try to find a good oil for a Honda z50 i use a semi-sinthectic oil and filler up till the oil is imbetween low and hi markers on the dipstick remember to dump old oil before replacing.