My guess is that bad timing and carb setting probably will give you more in bad running and
poor performance than actual damage, unless you ran it as hard as you could for a long time.
I suggest you find out what the condition REALLY is with a compression test, etc.
Immediate result of retarded ignition is low power and burned exhaust pipes and manifold.
If the manifold and pipes have not glowed red or cracked, you probably have not damaged them.
Bearings are damaged by running without oil.
If your valve clearance has not decreased, you probably have not hurt them either.
Don't listen to scare tactics, just fix the problems!
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George Downs, Bartlesville, Heart of the USA!