I just want to add my experience to the database. This is what happens when you have a Broken Head Gasket on a Kohler K321 Engine.
Engine Losing Power under Load
White Smoke coming from engine area other than exhaust
Engine Stalling Under Load
Discovered Head gasket broke towards front of engine. Losing Compression.
Replaced Head Gasket
This is what a broken head gasket looks like for those of you who have never seen it.
14 HP Kohler K321AS