I was gonna guess .018 - .020 and usually, the old set of points has the metal spring band that when unscrewed from the post where the wire goes, it can be bent away and used as a feeler guage to set the new points with. Its in the correct thickness range ifn' I remember right.
Make sure you have 12 volts at the points with the ignition on.
Make sure when points close, they are all the way closed.
Are you points clean?
Make sure your condensor is grounded with the lead going to the points (alot of jap bikes have the condensor mounted by the coil with the lead going to one of the terminals (-)on the coil(s))
Make sure the other terminal (+) on the coil goes to the IGN terminal on the switch.
Do you know your coils are OK? Check with ohmeter usually they are 3 - 6 ohm but I'm not a jap guy.
Sounds to me that you have a fairly simple problem.