Have a John Deere lawn tractor with no manual. Wonder where to check the oil? There is no visible dip stick.

Don't know the model, look for a 'Plug"/ cap on the motor above the "Base" of the motor, not the plug to drain the oil. Many small engines don't have what looks like a dip stick Handel. It may be on under the cap to where you add oil.

I looked up the 160 and it seems to be a 13 & 15 HP Kawasaki engine in it below is a parts blow out see if it looks looks like your engine

http://www.j-thomas.com/catalog/166_kawasaki_kai_engine_fh430v.html

Look at 44 on picture