MZ/MuZ Riders

Gentlemen ,

I am the new owner of a 1968 ES 175/2 Trophy (Yeah, the red one) , Im looking for a manual but in the meantime Im wanting to change fluids. I'm running 33-1 oil ratio that I learned here on this forum as well as use 1 liter of 85w90. Now my question is: I have three drain plug looking things on the bottom of my engine, from left side to right they are small/medium/large and there is what looks to be a filler almost above the middle (medium size) plug. If nobody knows off the top, I'll take pictures, so....which is the drain and what are the others?

Thank You, I love my MZ and I dont want to blow it up out of stupidity.

BTW this is not my engine but some image off the great and all powerful intranet.

The large is for oil draining, the other ones are for gearchange adjust. So don´t touch these unless you want to pull the engine apart..

thank you, that is exactly what I needed to hear. I did order a manual but the unknown age and quality of gear oil concerns me. Again, thanks,