OK. I assume you set the timing when it was running. Correct?
Since you cannot check the timing now,
did you check the point gap after it stopped working? I'm not doubting you or your previous efforts, but something has changed and we need to start with the basics and work up. You stated earlier that you have fire at plugs and gas in the carb, so logically it has to be timing. Also the backfiring points to timing.
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
-Unknown-
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