Ok, so make sure you replace the starter oring with a genuine one, we've all tried other ones , but they're either too big, or too small or too fat, or too skinny and just don't seem to work right bringing you back to square one quickly.
The loose carby on the manifold is a concern and suggest to me that the oring is either not there, or squashed and flat(and probably hard) and therefore not doing it's job, so the engine sucks air, runs lean and over revs. I've taken a pic of the manifold you have and it shows where the oring should sit. Once you replace it with a nice new soft fresh one the carby should sit tight and not turn upward like it is in your photo. This would also be a good opportunity to make sure that the 2 phillips screws that hold the manifold to the block are tight(one on top and one on bottom), but dont rush out to remove it and replace the small oring between the block and manifold as this rarely gets damaged unless it is disturbed.
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If the carb still does not sit right after replacing the oring and wavy washer then we'll have to look at whether the 2 tangs on the manifold that hold the carb in place are intact or whether the carb itself is worn or damaged.