Porta Champ oil change question(s)

[Atabuoy]

Have acquired a single cylinder Porta Champ, single cylinder. Circa early ‘90’s. Excellent condition. Doubtful oil has ever been changed? Don’t see a dip stick or sight glass? Have opened fill plug, can see some oil. I’d like to know what the fill capacity is? E.g., till it over flows or a specific quantity?
Appreciate any comments or advice.
thank you

 

[Sumboodie]

I'd guess level to the fill hole that's on the side of the pump facing the motor. Lot of small engines were like that years ago. Probably some still are, haven't worked on much new stuff.

 

[nadogail]

Fill the oil to the bottom of the threads of the opening where the Drain Plug screws in, the oil should be high enough that you can touch it with your extended smallest finger; but low enough to not cover the threads that will receive the plug.

 

[The Cobbler]

most likely fill to top of fill plug opening