Here is something I found doing a search on the web.
=========================
Kohler Engine Identification Numbers:
The engine model and serial numbers appears on a metal tag or decal that's attached or affixed to the flywheel shroud, on the carburetor side of the engine. But if there's no metal tag or decal that originally came with the engine, or if the engine block was replaced with a replacement short block or if the blower shroud has been replaced, there's no way of knowing exactly what year the engine is. All you'll know is the year of the blower shroud itself. Tags/decals and flywheel shrouds can be swapped from one engine to another and there are no numbers or identification characteristics on the blocks themselves (except for the 10hp through 14hp engines has 9 head bolts, the 16hp has 10 head bolts and the 18hp is OHV). Therefore, to see what size the engine actually is, it's best remove the cylinder head and measure the bore and stroke to determine engine size. Because a 10hp can be bored and stroked to a 12hp, using a 12hp piston, rod and crank, and a 12hp can be bored to a 14hp, using a 14hp piston, rod and crank.
