Yes replace the exhaust coupler, also add a rubber band on your carby to close the carby as a fail safe. I have had a few HoBao engines that the carby action wasn't smooth causing me issues. Some people have replaced the carby to a Novarossi one as a solution and this has also helped with tuning. But remember this is a cheap engine so don't spend a heap of money trying to get it too run.
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