voltage regulator/rectifier or the charging coil in my 1995 yamaha ca50 scooter

hello I know this isnt a motercyle foram but i have a technical question . I have a 1995 yamaha 50cc scooter it is not charging the battery but runs great!,i put in a new battery and cleaned all the conections and also cleand all the surfaces in the mageto/stator. i tested the recifier and it had resistance in one direction as i beleive that means it working the problem is low voltage to the battery and the battry keeps going dead the machine was run without a battery for a while so my question is it likely the voltage regulator or is the charging coil overworked and burnt out the is resistance to the stator so im not sure if its going out or not any suggestions would be helpfull p.s this is a 2-cycle engine with a seperate regulator/rectifier and thoughts thank you briguyman.