thanks , i've already seen it , but what i really am searching is some more detailed info ; how much oil in gear box, how to adjust the carburator , etc...
As far as serious details, BCS manuals lack. BCS America never even had a shop manual for the 700 and 800 series from 1995 to early 2000 and I didn't see any shop manuals on the pages I showed you, either. They had parts breakdowns, but no shop manuals. It's mind boggling that BCS America hands dealers a shop manual for the 715, 725, and 735 from the 1980's and expects them to work on an 853 with them. Lucky for you, though, since you have a 715...
Carb adjustments and such would be covered by the manual for your engine. I do not know of any site that has Acme service manuals up.
Here's a quick answer to your questions. Use gear oil SAE 80-90 wt rated GL-5 for the tractor and tiller gearboxes. Fill the tractor gearbox to the upper mark on the dipstick with the tractor sitting level. Fill the tiller gearbox to within 2" of the top of the fill hole again with the gearbox sitting level. Tiller gear oil should be changed with each set of replacement tines.
The carburetors are mostly all fixed main jet so the only adjustment is the low speed mixture. Adjust the screw on the side for smooth running at about 1800 rpm. Don't mess too much with the carburetor as the parts are not available.