Halfway up into the Escalante Range in Utah I had a similar problem from contaminating my oil. Ran half the day with my choke on. Saved my bacon by doing a quick oil change up off the road. If you let it go until the engine stopped your lower end is toast and a rebuilt switch-out is in order. Oil is always important, but moreso on an aircooled.

__________________
89 300E
79 240D
72 Westy
63 Bug sunroof
85 Jeep CJ7
86 Chevy 6.2l diesel PU

"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."
Marcus Aurelius