There is nothing in an engine that changes after breaking in....The piston rings gradually wear to fit the bore, the crank seals get a little looser, NOTHING else...If it shakes when new with the carb PROPERLY adjusted it will shake just as much after 100 gallons of fuel has been run through it, if it still runs

There is no carb on the planet that needs 6 turns out on the low needle to run...Anything over 3 turns open will only cause the needle to fall out in flight...
If a carb needs more than 2 turns open to run there is another problem somewhere...
Factory settings are a myth, no one can predict what the operating conditions will be...If you start with 2 turns open on both and the engine will not start, the problem is either a bad carb or a leak somewhere...
It's too bad ALL manufactureres and/or dealers don't run ALL engines before shipping, many problems could be fixed at the beginning.
Too many dealers just want to turn a quick profit, buy some cheap Chinese engines and get them out as quickly as possible...
I AM NOT BEING RACIST BY REFERRING TO ENGINES MADE IN CHINA AS CHINESE ENGINES.. If SOMEONE (YOU KNOW WHO YOU ARE) COULD TELL ME WHAT ELSE TO CALL CHINESE ENGINES I WILL "MAYBE" DO IT....
And SOMEONE is also getting some flak on the OTHER engine site for questionable advertising....Nuff said