I have a 14hp kohler engine in a 1980 john deere skid steer, I have put on new batteries but they don't stay charged, I replaced the regulator but still doesn't charge, what could I do next thanks John

Do you have a generator or an alternator? If you have a voltage regulator sounds like you may have a generator. If so check brushes in generator.

Have you tested the unit for output on the charging system?

No I haven't, Should it test between 10 to 12 amps, and is the starter act like a generator, also does the regulator need to be polared, thanks john

Should probably test about 14 volts. (volts, not anps). No, I don't think the starter can double as a generator.
Have you checked to make sure that you don't have something draining the battery while you sleep?

I have a 14 horse kohler in my 310 bobcat. I had a problem like yours. If it sat more than a day it was dead. I had a short between the switch and the starter. Fixed that and it has been great ever since.
Mike
PS my generator puts out between 14 - 15 volts when charging.