The 247cc engine was rated at 10hp, or 14hp on the supers (they had two little HL carbs hooked up with a progressive linkage!)
The 300's were 12hp to 16hp, depending on year, and carb.
320's were 18hp, and there were two or 3 versions of the 335. There was a free-air jug and sunburst head ported to deliver about 30hp for the 335, and guys would port them and shave heads for even more power.
Almost universally, they'd stick the pistons. I saw a Sachs (very similar) stick a piston so hard that it broke the ears off the jug and the jug/piston weldment would go up and down. Those cast-iron cylinders didn't expand like aluminum, and soon piston clearance was no more.
Dykes rings and increased piston clearance helped, but at power levels approaching 90bhp/liter, useful engine life was poor. My uncle built and raced sleds in those days; the old 297 Sachs (very similar) in full race mode wouldn't make it to the end of a cross-country race (100 miles).