Frank M:
The KT-17 Series II motors and the M-18 are basically the same, except for the Oil Filter and Solid State Ignition.
The KT-17 had two series of Motors, being Series I and Series II. Series I had a partial pressurized lubrication system in them. Kohler had a lot of problems with this series of motor if they were used on non-level applications (ie: mowing a ditch bank, etc.) If the motor was tilted just right, one could starve the Oil Pickup Tube. I have a friend of mine that has a KT-17 Series I in a 682 and he has not had a single issue since the tractor was new in 1982. His lawn is flat. LOL
Attached, is a diagram from the Kohler Service Manual that shows the type of lubrication system in the KT-17's:
Attached is the Lubrication system from the M-18 Service Manual:
As you can see, the lubrication system of the KT-17 Series II and the M-18 are the same.
As stated before, some of the KT-17 Series II motors had the option of installing a Oil Filter, on the block or remote. Those motors had a block off/ByPass plate attached to the block. Although, not all KT-17 Series II motors had this option, of which mine was one of those.
I hope this sheds some light on your inquiry.